# The macrophage-derived motor protein KIF13B enhances MERTK-mediated efferocytosis and prevents atherosclerosis in mice Researcher: Ge Zhang Chinese name: 张格 ORCID identity anchor: https://orcid.org/0000-0002-3116-3246 Canonical researcher: https://drgezhang.com/#person Journal: European Heart Journal Year: 2025 Type: Article DOI: 10.1093/eurheartj/ehaf523 Canonical page: https://drgezhang.com/papers/doi-10-1093-eurheartj-ehaf523.html Markdown record: https://drgezhang.com/papers/doi-10-1093-eurheartj-ehaf523.md ## Full Authors 1. Yitong Xu 2. Jingxuan Chen 3. Yiran Liu 4. Ge Zhang 5. Guolin Miao 6. Jingdong Wu 7. Kaikai Lu 8. Yinqi Zhao 9. Wenxi Zhang 10. Liwen Zheng 11. Lianxin Zhang 12. Jinxuan Chen 13. Zihao Zhou 14. Yufei Han 15. Pingping Lai 16. Jiabao Guo 17. Donghui Wu 18. Si Mei 19. Ling Zhang 20. Yang Zhao 21. Wei Huang 22. Yuhui Wang 23. Junnan Tang 24. Dongyu Zhao 25. Xunde Xian ## Official Abstract ### Background and Aims Atherosclerosis is a chronic inflammatory disorder with high morbidity and mortality rates worldwide. Emerging evidence has reported that kinesin family member 13B (KIF13B), a crucial motor protein, integrates hepatic lipid metabolism and inflammatory response to protect liver disease. However, the relationship between KIF13B and atherosclerosis remains unknown. The present study aimed to elucidate the specific role of KIF13B in atherosclerosis and its potential therapeutic significance. ### Methods The investigation first assessed the relationship between the expression levels of KIF13B and the progression of atherosclerosis in human cohort data and carotid plaques from patients. Subsequently, the authors generated Kif13b knockout (Kif13b−/−) mice on low-density lipoprotein receptor (Ldlr)-deficient background (Ldlr−/−) to obtain double knockouts (Kif13b−/−;Ldlr−/−) and myeloid-specific Kif13b knockout mice (Lyz2 Cre;Kif13bf/f) with adeno-associated virus 8 (AAV8)-mediated overexpression of proprotein convertase subtilisin/kexin type 9 (PCSK9). Moreover, Ldlr−/− mice received bone marrow transplants from either Kif13b−/−;Ldlr−/− or Ldlr−/− mice and were fed a Western diet (WD) for 12 weeks. ### Results KIF13B expression was significantly reduced in patients with atherosclerosis and negatively associated with the severity of atherosclerotic progress in WD-fed Ldlr−/− mice. In contrast to Kif13b−/−;Ldlr−/− mice showing a significant increase in plasma total cholesterol and more atherosclerosis lesions compared with the corresponding control mice, depletion of myeloid-derived Kif13b and bone marrow transplantation with macrophages lacking Kif13b both did not alter plasma lipid levels but elicited the larger atherosclerotic plaques with increased macrophage infiltration and more apoptotic cells. In vitro studies showed that upon oxidized low-density lipoprotein treatment, macrophages with Kif13b deficiency also display significantly increased cholesterol accumulation and impaired efferocytosis with reduced MER proto-oncogene, tyrosine kinase (MERTK) expression. Mechanistic study revealed that loss of Kif13b decreased the expression of Itchy E3 ubiquitin protein ligase (ITCH), leading to accelerated ubiquitination and degradation of MERTK mediated by Casitas B-lineage lymphoma (CBL) in macrophages. Moreover, oral administration of NX-1607, a CBL antagonist, significantly reversed the reduction of MERTK protein level and defective efferocytosis, ultimately protecting against atherosclerotic development caused by Kif13b deficiency in vivo. ### Conclusions The study results revealed that KIF13B is a crucial modulator responsible for maintaining proper macrophage efferocytosis to prevent atherosclerotic development through KIF13B/ITCH/CBL/MERTK axis, suggesting that KIF13B will be a potential therapeutic target for the treatment of atherosclerosis in future clinical trials. Text reproduced verbatim from publisher ([source](https://academic.oup.com/eurheartj/article/46/45/4969/8212255)); [DOI](https://doi.org/10.1093/eurheartj/ehaf523); [OUP-AUTHOR-ABSTRACT-REUSE](https://academic.oup.com/pages/open-research/open-access/charges-licences-and-self-archiving/author-self-archiving-policy). ## Research & review context ### Research fields - Atherosclerosis research - Innate immune vascular biology ### Review topics - Macrophage efferocytosis in plaque - Post-translational control of apoptotic-cell clearance ### Scientific role Macrophage KIF13B mechanism study connecting MERTK regulation, efferocytosis and experimental atherosclerosis. ### Evidence position Mouse and macrophage perturbation and rescue experiments with associative human plaque observations; preclinical plaque protection, not proven human treatment efficacy. ### Related concepts - Myeloid plaque biology - Efferocytosis-regulatory mechanisms ### Possible citation contexts - Background: defective apoptotic-cell clearance in atherosclerosis. - Mechanistic evidence: experimental regulation of macrophage efferocytosis, distinct from VSMC KIF13B state remodeling. Possible literature-review contexts, not evidence of existing citations. Read the findings and Evidence Scope before citing the original article. ## Evidence Scale **The macrophage-derived motor protein KIF13B enhances MERTK-mediated efferocytosis and prevents atherosclerosis in mice** A mechanistic translational preclinical study linking myeloid KIF13B to MERTK-dependent efferocytosis and experimental plaque protection, with associative human tissue evidence and article-reported NX-1607 rescue in cells and mice. | Evidence | Value | | --- | --- | | GSE40231 arterial-wall samples | STAGE/CABG human dataset: 40 non-atherosclerotic arterial-wall samples and 40 atherosclerotic arterial-wall samples; these are sample counts, not 80 unique participants. | | Human carotid lesion tissues | Early lesions n=6 and advanced lesions n=6. | | Mouse plaque progression | Ldlr-deficient mice after Western diet for 12 or 20 weeks; n=6 mice per group. | | Global Kif13b loss | Ldlr-deficient control and Kif13b-deficient Ldlr-deficient mice after 12 weeks of Western diet; n=6 mice per group. | | Public single-cell GSE155513 | Figure 3 describes n=1 single-cell library at each 8-week and 26-week dietary time point; do not treat library counts as mouse counts. | | Study-generated aortic single-cell experiment | Five mice pooled into one single-cell library per genotype; the Results state 20 weeks of Western diet while Figure 3E states 12 weeks of high-fat diet. | | Public macrophage single-cell GSE215103 | Reanalysis of Apoe-deficient mouse peritoneal macrophages; no unique mouse or library count inferred here. | | Myeloid conditional model | Kif13b-floxed controls n=9 versus Lyz2-Cre;Kif13b-floxed mice n=6, AAV8-PCSK9 and 12 weeks of Western diet. | | Bone-marrow transplantation | Ldlr-deficient recipients of control or Kif13b-deficient donor marrow; n=6 mice per group after 12 weeks of Western diet. | | BMDM transcriptomics | Wild-type versus Kif13b-deficient BMDMs n=3 per group, including apoptotic-cell co-incubation transcriptomics n=3 per group. | | NX-1607 mouse intervention | Ldlr-deficient and Kif13b-deficient Ldlr-deficient mice, n=6 per group; 20 weeks total Western diet with 5 mg/kg/day NX-1607 only during the final 16 weeks. | ### Counting note Counts have different denominators: human tissue samples, mice, pooled single-cell libraries, independent cultures or experiments. They cannot be summed as unique participants or independent biological replicates. Five mice pooled to one library per genotype are not five independent libraries; the generated single-cell experiment has conflicting Results and Figure 3E diet durations. ## Research Question Does KIF13B restrain experimental atherosclerosis by preserving macrophage MERTK-dependent efferocytosis through a post-translational ITCH/CBL regulatory network, and can pharmacologic intervention rescue impaired efferocytosis and atherosclerotic phenotypes in experimental models? Human tissue observations are associative; causal and pharmacologic tests are preclinical. ## Author Evidence Summary The study combined associative human arterial and carotid-plaque observations with mouse atherosclerosis genetics, public and study-generated single-cell/transcriptomic analyses, macrophage experiments, genetic rescue and preclinical pharmacologic intervention. KIF13B expression was lower in advanced human arterial/plaque tissue and progressing mouse plaques. Global Kif13b loss worsened atherosclerosis in Ldlr-deficient mice but increased circulating lipids in that model. Myeloid-specific deletion and Kif13b-deficient bone-marrow transplantation worsened lesion burden, necrotic cores, macrophage and apoptotic-cell accumulation without corresponding plasma-lipid changes, supporting a local myeloid/hematopoietic contribution in mice. Kif13b-deficient macrophages showed impaired efferocytosis and lower MERTK protein; restoring MERTK in deficient BMDMs improved efferocytosis. Unchanged Mertk mRNA, reduced MERTK protein stability, proteasome dependence, increased MERTK ubiquitination, KIF13B/ITCH interaction and ITCH/CBL/MERTK rescue results support a post-translational regulatory model, although the exact proposed ITCH-mediated CBL degradation step remains incompletely demonstrated. The article reported that NX-1607 improved MERTK/efferocytosis phenotypes in macrophages and reduced atherosclerotic phenotypes in mice. The article describes NX-1607 as a CBL inhibitor, whereas external authoritative drug-development sources identify it as a CBL-B/CBLB inhibitor; CBL and CBLB are distinct genes. Thus NX-1607 is reported as preclinical pharmacologic rescue, not unambiguous target validation of endogenous CBL. No human atherosclerosis treatment efficacy was tested. ## Key Findings ### KF1: KIF13B expression is lower in advanced human arterial and carotid lesions and in progressing mouse plaques. Context: Human findings are associative, not evidence that manipulating KIF13B changes human atherosclerosis. | Evidence | Value | | --- | --- | | GSE40231 | 40 non-atherosclerotic and 40 atherosclerotic arterial-wall samples showed lower KIF13B in atherosclerotic tissue. | | Human carotid tissue | Early n=6 and advanced n=6 lesions showed lower KIF13B protein in advanced plaques, with macrophage co-localization. | | Mouse progression | Ldlr-deficient mice, n=6 per group, showed lower plaque KIF13B after 20 versus 12 weeks of Western diet. | Source locator: Results: The expression of KIF13B is negatively correlated with the progression of atherosclerosis in patients and mice; Figure 1 and Supplementary Figure S1. ### KF2: Global Kif13b loss worsened experimental atherosclerosis in Ldlr-deficient mice, but circulating lipids also increased in that model. Context: The global Ldlr-deficient comparison does not isolate a lipid-independent mechanism; Apoe-background observations did not show the same lipid effect. | Evidence | Value | | --- | --- | | Ldlr model | After 12 weeks of Western diet, control versus global Kif13b-deficient Ldlr-deficient mice had n=6 mice per group; lesions and circulating total cholesterol and triglycerides increased with Kif13b loss. | | Plaque phenotype | Necrotic-core area rose up to approximately twofold, CD68-positive macrophage infiltration more than threefold, and apoptotic-cell accumulation increased. | | Apoe background | Worsened plaques were also reported in the Apoe-deficient background without the same circulating-lipid change. | Source locator: Results: Deletion of Kif13b in Ldlr−/− mice exacerbates atherosclerosis; Figure 2 and Supplementary Figure S2. ### KF3: Single-cell and macrophage analyses implicated altered macrophage states with lower Kif13b during experimental atherosclerosis. Context: The study-generated aortic single-cell comparison pooled five mice into one library per genotype; Results and Figure 3E disagree on diet duration, so no single definitive duration is assigned. | Evidence | Value | | --- | --- | | GSE155513 | Figure 3 uses one single-cell library at each 8-week and 26-week high-fat-diet time point; macrophage abundance rose and Kif13b reduction was prominent in macrophages. | | Study-generated single-cell | Five aortas were pooled per genotype into one library, yielding 14 clusters and eight cell types; Cd80-positive, Il1b-positive, Spp1-positive and Cd206-positive macrophage states were emphasized, with Kif13b loss associated with fewer Cd206-positive and more Il1b-positive and Spp1-positive states. | | Independent observations | GSE215103 Apoe-deficient macrophage reanalysis and ox-LDL-treated BMDM and THP-1 experiments also showed lower KIF13B. | Source locator: Results: Kif13b deficiency primarily affects macrophage dynamics in mouse atherosclerosis; Figure 3. ### KF4: Myeloid conditional deletion and Kif13b-deficient bone-marrow transfer worsened plaque phenotypes without corresponding plasma-lipid changes in their mouse models. Context: These results support a lipid-independent myeloid or hematopoietic contribution in the tested models, not a macrophage-exclusive or proven human causal effect. | Evidence | Value | | --- | --- | | Lyz2-Cre model | Kif13b-floxed controls n=9 versus Lyz2-Cre;Kif13b-floxed mice n=6 after AAV8-PCSK9 and 12 weeks of Western diet; lesions, necrotic core, macrophages and apoptotic cells increased without material total-cholesterol, triglyceride or lipoprotein differences. | | Bone-marrow transfer | Ldlr-deficient recipients of control versus Kif13b-deficient donor marrow, n=6 per group after 12 weeks of Western diet, showed worse plaque outcomes without plasma-lipid change. | Source locator: Results: Myeloid-specific deletion of Kif13b aggravates atherosclerosis in a lipid-independent manner; Figure 4 and Supplementary Figures S3–S4. ### KF5: Kif13b-deficient macrophages had impaired efferocytosis and reduced MERTK protein; restoring MERTK in deficient BMDMs improved efferocytosis. Context: The genetic rescue was a macrophage cell experiment, not a demonstrated in vivo MERTK therapy or human rescue. | Evidence | Value | | --- | --- | | Transcriptomics | Wild-type and knockout BMDM RNA-seq n=3 per group and apoptotic-cell co-incubation RNA-seq n=3 per group nominated efferocytosis pathways. | | Functional phenotype | BMDM efferocytosis assays n=5 per group and MERTK immunofluorescence n=10 per group implicated lower MERTK among evaluated efferocytosis proteins; in vivo conditional and marrow-transfer models also had impaired efferocytosis. | | MERTK restoration | MERTK restoration in Kif13b-deficient BMDMs improved efferocytosis; western blot n=3 per group and efferocytosis rescue n=10 per group. | Source locator: Results: Loss of Kif13b inhibits MERTK-mediated macrophage efferocytosis; Figure 5. ### KF6: The KIF13B–ITCH–CBL–MERTK data support post-translational MERTK regulation, while the exact proposed ITCH-mediated CBL degradation step remains incompletely demonstrated. Context: CBL is the endogenous gene/protein investigated; CBLB is distinct. Unchanged Mertk mRNA argues against a transcriptional explanation of lower MERTK protein in this experiment. | Evidence | Value | | --- | --- | | MERTK turnover | Mertk mRNA was unchanged in compared BMDMs n=3 per group; in THP-1 knockdown cells MERTK protein fell to about 40% at 16 hours of cycloheximide chase. | | Protein mechanism | Proteasome inhibitor MG132 at 10 µM, but not chloroquine at 10 µM, blocked MERTK loss; MERTK ubiquitination and CBL protein increased with KIF13B loss. | | ITCH interaction and rescue | KIF13B and ITCH co-immunoprecipitated, ITCH fell with KIF13B loss, and ITCH overexpression in deficient BMDMs reversed higher CBL and lower MERTK; direct proof of each proposed ITCH-to-CBL degradation step is incomplete. | | Human association | Advanced human plaque tissues n=6 per group showed lower KIF13B, ITCH and MERTK and higher CBL; this is associative. | Source locator: Results: KIF13B decreases CBL-mediated ubiquitination of MERTK by interacting with itch in macrophages; Figure 6. ### KF7: NX-1607 improved MERTK and efferocytosis phenotypes in macrophages and reduced atherosclerotic phenotypes in mice; its target identity does not unambiguously validate endogenous CBL. Context: The article calls NX-1607 a CBL inhibitor, while external authoritative drug-development sources identify it as a CBL-B/CBLB inhibitor; CBL and CBLB are distinct genes. These are preclinical rescue results, not human atherosclerosis treatment efficacy. | Evidence | Value | | --- | --- | | Macrophage assays | NX-1607 at 50 nM increased MERTK in BMDMs; MERTK/CBL western blot n=3 per group, efferocytosis at DMSO, 50 and 100 nM n=10 per group, and 50 nM co-immunoprecipitation in three independent experiments were reported. | | Mouse schedule and outcome | Ldlr-deficient and Kif13b-deficient Ldlr-deficient mice received 20 weeks total Western diet, with NX-1607 5 mg/kg/day only in the final 16 weeks, n=6 per group; plaque burden, necrotic core, macrophage and apoptotic-cell accumulation declined, and MERTK/efferocytosis increased without reported lipid change. | | Safety and clinical boundary | ALT and AST showed no reported liver-toxicity signal in these mouse measurements, but white blood cells and lymphocytes declined; NCT05107674 is a Phase I advanced-malignancy trial, not an atherosclerosis trial. | Source locator: Results: The CBL inhibitor NX-1607 effectively ameliorates atherosclerosis by enhancing macrophage efferocytosis; Figure 7 and Supplementary Figures S6–S7. ## Study Design & Analytical Framework ### Study profile - Study Design: Mechanistic translational preclinical study combining associative human arterial and plaque observations with mouse atherosclerosis genetics, public and study-generated transcriptomics, macrophage experiments, genetic rescue and pharmacologic intervention. - Evidence Type: Human tissue association; causal mouse and macrophage experiments; public dataset reanalysis; preclinical pharmacologic rescue. - Population: Human arterial-wall and carotid-plaque tissue samples; Ldlr-deficient and Apoe-deficient mouse models; mouse bone-marrow-derived macrophages and THP-1 cells. No treated human atherosclerosis cohort. - Primary Endpoint: Experimental atherosclerotic lesion burden and macrophage efferocytosis across genetic and pharmacologic models. - Secondary Endpoint: Plaque necrotic core, macrophage and apoptotic-cell accumulation, circulating lipids, MERTK protein regulation and reported safety observations. - External dataset evaluation: Yes - Data modalities: Human tissue expression and immunostaining, Mouse plaque histology and plasma lipids, Public and pooled aortic single-cell RNA sequencing, BMDM RNA sequencing, Macrophage efferocytosis and protein assays, Genetic rescue and preclinical pharmacology ## What This Study Adds - Connects lower KIF13B in human arterial and plaque tissue with experimental genetic evidence from mouse atherosclerosis without treating human associations as causal. - Separates the lipid-confounded global Ldlr-deficient knockout from myeloid conditional and marrow-transfer phenotypes that occurred without corresponding plasma-lipid changes. - Links KIF13B loss to impaired macrophage efferocytosis and lower MERTK protein, with cell-level MERTK restoration supporting functional involvement. - Proposes a post-translational KIF13B–ITCH–CBL–MERTK regulatory network while acknowledging that the precise ITCH-mediated CBL degradation step remains incompletely proven. - Reports preclinical NX-1607 rescue while explicitly separating article-described CBL inhibition from external CBL-B/CBLB target identification and from clinical efficacy. ## Evidence Scope ### Supports - Association between lower KIF13B and advanced human arterial or carotid-plaque tissue, and progression in mouse plaque observations. - Causal worsening of mouse plaque phenotypes after global, myeloid or hematopoietic Kif13b perturbation within their respective experimental models. - A myeloid or hematopoietic contribution without corresponding plasma-lipid differences in conditional and transplantation models, separate from the lipid increase in global Ldlr-deficient knockout mice. - Reduced MERTK protein and efferocytosis after Kif13b loss and improvement of BMDM efferocytosis following MERTK restoration. - Evidence consistent with post-translational ITCH/CBL/MERTK regulation and article-reported NX-1607 rescue in macrophages and mice. ### Does Not Establish - Human KIF13B causality, prediction of clinical outcomes or human atherosclerosis treatment efficacy. - That the global Ldlr-deficient knockout plaque phenotype is lipid independent. - Macrophage-exclusive effects of Lyz2-Cre deletion or bone-marrow transplantation, or five independent single-cell libraries from five pooled mice. - One definitive diet duration for the study-generated pooled aortic single-cell comparison, because Results and Figure 3E disagree. - That MERTK restoration is an effective in vivo or human therapy, or that every proposed ITCH-to-CBL ubiquitination and degradation step has been directly resolved. - That NX-1607 reverses 20 weeks of established disease, has proven human atherosclerosis benefit, or unequivocally validates endogenous CBL rather than the distinct CBLB target described by external sources. ### Limitations - Human arterial-wall and carotid-plaque results are associative tissue observations with small carotid groups, not causal human intervention evidence. - The global Kif13b-deficient Ldlr model had higher circulating cholesterol and triglycerides, limiting attribution of its plaque phenotype solely to local plaque biology. - Lyz2-Cre targets myeloid lineages and donor-marrow transplantation changes hematopoietic compartments; neither isolates macrophages exclusively. - Study-generated single-cell data pooled five mice to one library per genotype, limiting independent biological replication at the library level. - The Results and Figure 3E give discordant 20-week Western-diet and 12-week high-fat-diet descriptions for the pooled aortic single-cell experiment. - GSE155513 Figure 3 time points use one single-cell library each; sample and library counts must not be conflated. - MERTK restoration rescue was demonstrated in Kif13b-deficient BMDMs, not as an in vivo MERTK treatment. - The exact ITCH-mediated CBL ubiquitination/degradation step in the proposed network remains incompletely demonstrated; MERTK regulation is not fully assigned to one mechanism. - The article's CBL-inhibitor description of NX-1607 conflicts with external CBL-B/CBLB target identification, preventing unambiguous pharmacologic validation of endogenous CBL. - NX-1607 was tested preclinically during the final 16 of 20 Western-diet weeks, not as reversal after 20 weeks of established disease; no human atherosclerosis efficacy was assessed. - Mouse NX-1607 measurements found no reported ALT/AST liver-toxicity signal but did report lower white blood cells and lymphocytes, so safety is not established. ## When This Study Is Useful to Cite ### CU1: What evidence links macrophage KIF13B to atherosclerosis? Human tissue associations and mouse genetic/single-cell experiments link lower KIF13B to atherosclerosis; human association is not human causality and pooled libraries are not independent mice. Evidence: [KF1](#kf1), [KF2](#kf2), [KF3](#kf3), [KF4](#kf4) ### CU2: How does KIF13B regulate macrophage efferocytosis through MERTK? KIF13B-deficient macrophages showed impaired efferocytosis and reduced MERTK protein, while MERTK restoration improved efferocytosis in deficient BMDMs. Evidence: [KF5](#kf5) ### CU3: What evidence supports post-translational regulation of MERTK by the KIF13B–ITCH–CBL network? Accepted protein-turnover and rescue evidence supports this model, but the exact proposed ITCH-mediated CBL degradation step remains incompletely demonstrated. Evidence: [KF6](#kf6) ### CU4: Does myeloid KIF13B affect experimental atherosclerosis independently of plasma lipid changes? Myeloid conditional deletion and marrow-transfer phenotypes occurred without corresponding lipid changes in the tested mouse models; the global Ldlr knockout is lipid-confounded. Evidence: [KF2](#kf2), [KF4](#kf4) ### CU5: What preclinical pharmacologic rescue evidence was reported for impaired KIF13B/MERTK efferocytosis? NX-1607 produced macrophage and mouse rescue in the reported experiments; evidence is preclinical and CBL versus CBLB target identity remains qualified. Evidence: [KF7](#kf7) ## What This Study Should Not Be Cited to Claim - Human tissue association is not human KIF13B causality or treatment efficacy. - The global Ldlr-deficient knockout model is confounded by increased circulating lipids. - Five pooled mice in one single-cell library are not five independent library replicates. - The exact proposed ITCH-mediated CBL degradation mechanism remains incompletely demonstrated. - CBL and CBLB are distinct and must not be conflated when interpreting NX-1607. - NX-1607 rescue is preclinical; no human atherosclerosis treatment efficacy was established. ## Evidence Matrix ### KF1: KIF13B expression is lower in advanced human arterial and carotid lesions and in progressing mouse plaques. - Context: Human findings are associative, not evidence that manipulating KIF13B changes human atherosclerosis. - Finding: KIF13B expression is lower in advanced human arterial and carotid lesions and in progressing mouse plaques. GSE40231: 40 non-atherosclerotic and 40 atherosclerotic arterial-wall samples showed lower KIF13B in atherosclerotic tissue.; Human carotid tissue: Early n=6 and advanced n=6 lesions showed lower KIF13B protein in advanced plaques, with macrophage co-localization.; Mouse progression: Ldlr-deficient mice, n=6 per group, showed lower plaque KIF13B after 20 versus 12 weeks of Western diet.. - Evidence Level: Human observational association - Scope: Human findings are associative, not evidence that manipulating KIF13B changes human atherosclerosis. - Source Locator: Results: The expression of KIF13B is negatively correlated with the progression of atherosclerosis in patients and mice; Figure 1 and Supplementary Figure S1. - Evidence refs: [KF1](#kf1) ### KF2: Global Kif13b loss worsened experimental atherosclerosis in Ldlr-deficient mice, but circulating lipids also increased in that model. - Context: The global Ldlr-deficient comparison does not isolate a lipid-independent mechanism; Apoe-background observations did not show the same lipid effect. - Finding: Global Kif13b loss worsened experimental atherosclerosis in Ldlr-deficient mice, but circulating lipids also increased in that model. Ldlr model: After 12 weeks of Western diet, control versus global Kif13b-deficient Ldlr-deficient mice had n=6 mice per group; lesions and circulating total cholesterol and triglycerides increased with Kif13b loss.; Plaque phenotype: Necrotic-core area rose up to approximately twofold, CD68-positive macrophage infiltration more than threefold, and apoptotic-cell accumulation increased.; Apoe background: Worsened plaques were also reported in the Apoe-deficient background without the same circulating-lipid change.. - Evidence Level: Preclinical experimental evidence - Scope: The global Ldlr-deficient comparison does not isolate a lipid-independent mechanism; Apoe-background observations did not show the same lipid effect. - Source Locator: Results: Deletion of Kif13b in Ldlr−/− mice exacerbates atherosclerosis; Figure 2 and Supplementary Figure S2. - Evidence refs: [KF2](#kf2) ### KF3: Single-cell and macrophage analyses implicated altered macrophage states with lower Kif13b during experimental atherosclerosis. - Context: The study-generated aortic single-cell comparison pooled five mice into one library per genotype; Results and Figure 3E disagree on diet duration, so no single definitive duration is assigned. - Finding: Single-cell and macrophage analyses implicated altered macrophage states with lower Kif13b during experimental atherosclerosis. GSE155513: Figure 3 uses one single-cell library at each 8-week and 26-week high-fat-diet time point; macrophage abundance rose and Kif13b reduction was prominent in macrophages.; Study-generated single-cell: Five aortas were pooled per genotype into one library, yielding 14 clusters and eight cell types; Cd80-positive, Il1b-positive, Spp1-positive and Cd206-positive macrophage states were emphasized, with Kif13b loss associated with fewer Cd206-positive and more Il1b-positive and Spp1-positive states.; Independent observations: GSE215103 Apoe-deficient macrophage reanalysis and ox-LDL-treated BMDM and THP-1 experiments also showed lower KIF13B.. - Evidence Level: Pooled single-cell or cellular experimental evidence - Scope: The study-generated aortic single-cell comparison pooled five mice into one library per genotype; Results and Figure 3E disagree on diet duration, so no single definitive duration is assigned. - Source Locator: Results: Kif13b deficiency primarily affects macrophage dynamics in mouse atherosclerosis; Figure 3. - Evidence refs: [KF3](#kf3) ### KF4: Myeloid conditional deletion and Kif13b-deficient bone-marrow transfer worsened plaque phenotypes without corresponding plasma-lipid changes in their mouse models. - Context: These results support a lipid-independent myeloid or hematopoietic contribution in the tested models, not a macrophage-exclusive or proven human causal effect. - Finding: Myeloid conditional deletion and Kif13b-deficient bone-marrow transfer worsened plaque phenotypes without corresponding plasma-lipid changes in their mouse models. Lyz2-Cre model: Kif13b-floxed controls n=9 versus Lyz2-Cre;Kif13b-floxed mice n=6 after AAV8-PCSK9 and 12 weeks of Western diet; lesions, necrotic core, macrophages and apoptotic cells increased without material total-cholesterol, triglyceride or lipoprotein differences.; Bone-marrow transfer: Ldlr-deficient recipients of control versus Kif13b-deficient donor marrow, n=6 per group after 12 weeks of Western diet, showed worse plaque outcomes without plasma-lipid change.. - Evidence Level: Preclinical experimental evidence - Scope: These results support a lipid-independent myeloid or hematopoietic contribution in the tested models, not a macrophage-exclusive or proven human causal effect. - Source Locator: Results: Myeloid-specific deletion of Kif13b aggravates atherosclerosis in a lipid-independent manner; Figure 4 and Supplementary Figures S3–S4. - Evidence refs: [KF4](#kf4) ### KF5: Kif13b-deficient macrophages had impaired efferocytosis and reduced MERTK protein; restoring MERTK in deficient BMDMs improved efferocytosis. - Context: The genetic rescue was a macrophage cell experiment, not a demonstrated in vivo MERTK therapy or human rescue. - Finding: Kif13b-deficient macrophages had impaired efferocytosis and reduced MERTK protein; restoring MERTK in deficient BMDMs improved efferocytosis. Transcriptomics: Wild-type and knockout BMDM RNA-seq n=3 per group and apoptotic-cell co-incubation RNA-seq n=3 per group nominated efferocytosis pathways.; Functional phenotype: BMDM efferocytosis assays n=5 per group and MERTK immunofluorescence n=10 per group implicated lower MERTK among evaluated efferocytosis proteins; in vivo conditional and marrow-transfer models also had impaired efferocytosis.; MERTK restoration: MERTK restoration in Kif13b-deficient BMDMs improved efferocytosis; western blot n=3 per group and efferocytosis rescue n=10 per group.. - Evidence Level: Preclinical experimental evidence - Scope: The genetic rescue was a macrophage cell experiment, not a demonstrated in vivo MERTK therapy or human rescue. - Source Locator: Results: Loss of Kif13b inhibits MERTK-mediated macrophage efferocytosis; Figure 5. - Evidence refs: [KF5](#kf5) ### KF6: The KIF13B–ITCH–CBL–MERTK data support post-translational MERTK regulation, while the exact proposed ITCH-mediated CBL degradation step remains incompletely demonstrated. - Context: CBL is the endogenous gene/protein investigated; CBLB is distinct. Unchanged Mertk mRNA argues against a transcriptional explanation of lower MERTK protein in this experiment. - Finding: The KIF13B–ITCH–CBL–MERTK data support post-translational MERTK regulation, while the exact proposed ITCH-mediated CBL degradation step remains incompletely demonstrated. MERTK turnover: Mertk mRNA was unchanged in compared BMDMs n=3 per group; in THP-1 knockdown cells MERTK protein fell to about 40% at 16 hours of cycloheximide chase.; Protein mechanism: Proteasome inhibitor MG132 at 10 µM, but not chloroquine at 10 µM, blocked MERTK loss; MERTK ubiquitination and CBL protein increased with KIF13B loss.; ITCH interaction and rescue: KIF13B and ITCH co-immunoprecipitated, ITCH fell with KIF13B loss, and ITCH overexpression in deficient BMDMs reversed higher CBL and lower MERTK; direct proof of each proposed ITCH-to-CBL degradation step is incomplete.; Human association: Advanced human plaque tissues n=6 per group showed lower KIF13B, ITCH and MERTK and higher CBL; this is associative.. - Evidence Level: Preclinical experimental evidence - Scope: CBL is the endogenous gene/protein investigated; CBLB is distinct. Unchanged Mertk mRNA argues against a transcriptional explanation of lower MERTK protein in this experiment. - Source Locator: Results: KIF13B decreases CBL-mediated ubiquitination of MERTK by interacting with itch in macrophages; Figure 6. - Evidence refs: [KF6](#kf6) ### KF7: NX-1607 improved MERTK and efferocytosis phenotypes in macrophages and reduced atherosclerotic phenotypes in mice; its target identity does not unambiguously validate endogenous CBL. - Context: The article calls NX-1607 a CBL inhibitor, while external authoritative drug-development sources identify it as a CBL-B/CBLB inhibitor; CBL and CBLB are distinct genes. These are preclinical rescue results, not human atherosclerosis treatment efficacy. - Finding: NX-1607 improved MERTK and efferocytosis phenotypes in macrophages and reduced atherosclerotic phenotypes in mice; its target identity does not unambiguously validate endogenous CBL. Macrophage assays: NX-1607 at 50 nM increased MERTK in BMDMs; MERTK/CBL western blot n=3 per group, efferocytosis at DMSO, 50 and 100 nM n=10 per group, and 50 nM co-immunoprecipitation in three independent experiments were reported.; Mouse schedule and outcome: Ldlr-deficient and Kif13b-deficient Ldlr-deficient mice received 20 weeks total Western diet, with NX-1607 5 mg/kg/day only in the final 16 weeks, n=6 per group; plaque burden, necrotic core, macrophage and apoptotic-cell accumulation declined, and MERTK/efferocytosis increased without reported lipid change.; Safety and clinical boundary: ALT and AST showed no reported liver-toxicity signal in these mouse measurements, but white blood cells and lymphocytes declined; NCT05107674 is a Phase I advanced-malignancy trial, not an atherosclerosis trial.. - Evidence Level: Preclinical experimental evidence - Scope: The article calls NX-1607 a CBL inhibitor, while external authoritative drug-development sources identify it as a CBL-B/CBLB inhibitor; CBL and CBLB are distinct genes. These are preclinical rescue results, not human atherosclerosis treatment efficacy. - Source Locator: Results: The CBL inhibitor NX-1607 effectively ameliorates atherosclerosis by enhancing macrophage efferocytosis; Figure 7 and Supplementary Figures S6–S7. - Evidence refs: [KF7](#kf7) ## KIF13B Atherosclerosis Evidence Network Shared entity: KIF13B; relationship: complementary cell-type-specific mechanisms. These studies provide complementary cell-type-specific experimental evidence for KIF13B in atherosclerosis, not independent replication of one identical mechanism. | Paper | Cell context | Mechanistic axis | Human evidence | Causal evidence | Preclinical intervention | Clinical boundary | | --- | --- | --- | --- | --- | --- | --- | | [The macrophage-derived motor protein KIF13B enhances MERTK-mediated efferocytosis and prevents atherosclerosis in mice](https://drgezhang.com/papers/doi-10-1093-eurheartj-ehaf523.html) ([DOI](https://doi.org/10.1093/eurheartj/ehaf523)) | macrophage / myeloid; experimental atherosclerosis | KIF13B → ITCH / CBL-related post-translational regulation → MERTK → efferocytosis | Associative human arterial/plaque evidence only | Preclinical mouse/macrophage experiments | NX-1607 rescue in macrophages and mice | The article calls NX-1607 a CBL inhibitor, while accepted evidence preserves CBL versus CBLB target-identity ambiguity; no human atherosclerosis treatment efficacy. | | [Vascular smooth muscle cell-derived KIF13B inhibits proinflammatory responses to protect against atherosclerosis](https://drgezhang.com/papers/doi-10-1172-jci194175.html) ([DOI](https://doi.org/10.1172/jci194175)) | vascular smooth muscle cell; experimental atherosclerosis / plaque stability | KIF13B → KCTD10-dependent KLF4 ubiquitination/proteasomal turnover → matrix/inflammatory VSMC state | Associative human plaque evidence only | Preclinical mouse/HASMC experiments | Kenpaullone rescue in cells and mice | Kenpaullone is not established here as a KLF4-selective human therapeutic; no human treatment efficacy. | - Human plaque observations are associative, not proof that KIF13B manipulation improves human ASCVD outcomes. - Neither experimental compound is an established human atherosclerosis therapy. ## Q&A ### What is the human evidence for KIF13B in atherosclerosis? KIF13B was lower in 40 atherosclerotic versus 40 non-atherosclerotic arterial-wall samples in GSE40231 and in advanced versus early carotid lesions (n=6 tissue samples per group). These are tissue associations; no human KIF13B intervention or causal human effect was tested. Evidence: KF1 ### Did Kif13b loss worsen mouse plaques independently of circulating lipids? Global Kif13b deletion in the Ldlr-deficient model worsened plaques and increased total cholesterol and triglycerides, so that comparison is lipid-confounded. Lyz2-Cre myeloid deletion and Kif13b-deficient donor-marrow transfer worsened lesion, necrotic-core, macrophage and apoptotic-cell outcomes without corresponding plasma-lipid changes in their tested mouse models. These approaches are not macrophage-exclusive. Evidence: KF2, KF4 ### What do the single-cell experiments show, and how many independent libraries were there? Public datasets and the study-generated aortic comparison implicated macrophage state changes with lower Kif13b. The generated experiment pooled five mice into one library per genotype, not five independent libraries. Its Results describe 20 weeks of Western diet while Figure 3E describes 12 weeks of high-fat diet, so this page does not resolve the duration. Figure 3 uses one GSE155513 library per 8-week and 26-week time point. Evidence: KF3 ### Is MERTK involved in the efferocytosis phenotype, and was it rescued in vivo? Kif13b-deficient BMDMs had lower MERTK protein and impaired efferocytosis. Restoring MERTK in deficient BMDMs improved efferocytosis, supporting functional involvement in cells. This was not a demonstrated in vivo MERTK-restoration therapy or human treatment. Evidence: KF5 ### How certain is the proposed KIF13B–ITCH–CBL–MERTK mechanism? Unchanged Mertk mRNA, faster MERTK protein loss, proteasome-sensitive degradation, increased MERTK ubiquitination, KIF13B–ITCH interaction and ITCH overexpression rescue support a post-translational model. The precise proposed ITCH-mediated CBL ubiquitination/degradation step was not fully demonstrated; alternative routes including CBL self-ubiquitination remain possible. Evidence: KF6 ### What did NX-1607 do in cells and mice, and what safety findings were reported? In BMDMs, NX-1607 at 50 nM increased MERTK and 50–100 nM improved efferocytosis. In mice, 5 mg/kg/day was given only for the final 16 weeks of a 20-week Western-diet protocol, reducing plaque-related outcomes without reported lipid change. ALT/AST showed no reported liver-toxicity signal, but white blood cells and lymphocytes declined. This is preclinical intervention, not reversal after 20 completed weeks of established disease. Evidence: KF7 ### Has NX-1607 shown clinical benefit for atherosclerosis? No human atherosclerosis treatment efficacy was tested. NCT05107674 is a Phase I advanced-malignancy study, not an atherosclerosis trial; its existence does not establish clinical vascular benefit. Evidence: KF7 ### Does NX-1607 prove the endogenous CBL mechanism? No. The article describes NX-1607 as a CBL inhibitor, whereas external authoritative drug-development sources identify it as a CBL-B/CBLB inhibitor. CBL and CBLB are distinct genes. The observed preclinical rescue cannot by itself unambiguously assign the drug effect to the endogenous CBL mechanism proposed in this paper. Evidence: KF6, KF7 ## Concepts & Entities ### Conditions Atherosclerosis, Advanced atherosclerotic plaque, Plaque necrotic core, Atherosclerotic lesion progression ### Genes And Proteins KIF13B, MERTK, ITCH, CBL, CBLB (distinct from CBL), SPP1, IL1B, CD68, LYZ2, LDLR, APOE, PCSK9 ### Cells And Processes Myeloid cells, Macrophages, Bone-marrow-derived macrophages, THP-1 macrophages, Spp1-positive macrophages, Cd206-positive macrophages, Il1b-positive macrophages, Cd80-positive macrophages, Efferocytosis, Apoptotic-cell clearance, Protein ubiquitination, Proteasomal degradation, MERTK protein stability ### Models And Datasets Ldlr-deficient mouse, Kif13b-deficient Ldlr-deficient mouse, Apoe-deficient mouse, Lyz2-Cre conditional deletion, AAV8-PCSK9, Bone-marrow transplantation, Western diet, High-fat diet, ox-LDL, GSE40231, GSE155513, GSE215103 ### Intervention NX-1607 preclinical intervention ## Related Research - [Vascular smooth muscle cell-derived KIF13B inhibits proinflammatory responses to protect against atherosclerosis](https://drgezhang.com/papers/doi-10-1172-jci194175.html) — Complementary KIF13B work in vascular smooth muscle cells and atherosclerotic inflammatory responses; a distinct cell compartment and study. (DOI: 10.1172/jci194175) - [Smooth muscle cell fate decisions decipher a high-resolution heterogeneity within atherosclerosis molecular subtypes](https://drgezhang.com/papers/smc-fate.html) — Related atherosclerotic smooth-muscle-cell fate research, providing disease-context perspective rather than direct validation of the myeloid KIF13B mechanism. (DOI: 10.1186/s12967-022-03795-9) ## Publication & Provenance - DOI: https://doi.org/10.1093/eurheartj/ehaf523 - Doi: 10.1093/eurheartj/ehaf523 - Pmid: 40709729 - Publisher: Oxford Academic, European Heart Journal - Publisher: https://doi.org/10.1093/eurheartj/ehaf523 - Version Of Record: European Heart Journal 46(45):4969–4984; first published 25 July 2025. - Source Material: Publisher version of record, Supplementary Methods and Supplementary Figures S1–S7; public datasets GSE40231, GSE155513 and GSE215103. - Data Availability: The data underlying this article will be shared on reasonable request to the corresponding author. - Counting Note: Human samples, mice, cultures and pooled single-cell libraries are separate denominators; no overall unique n is inferred. - Scrna Duration Note: Study-generated aortic single-cell Results state 20 weeks of Western diet, whereas Figure 3E states 12 weeks of high-fat diet; five mice were pooled into one library per genotype. The discrepancy is not resolved here. - Nx Target Identity Note: The article describes NX-1607 as a CBL inhibitor; external authoritative drug-development sources identify it as a CBL-B/CBLB inhibitor. CBL and CBLB are distinct genes. NX-1607 rescue does not unambiguously validate the endogenous CBL mechanism. - Clinical Context Note: NCT05107674 is a Phase I study in advanced malignancies, not an atherosclerosis clinical trial; no human atherosclerosis treatment efficacy is established. ## Evidence-page notice This evidence page distinguishes associative human tissue observations from causal mouse and macrophage experiments. NX-1607 results are preclinical and do not establish human atherosclerosis efficacy or unambiguous pharmacologic validation of the endogenous CBL mechanism. The publisher article remains the authoritative record. ## Links - DOI: https://doi.org/10.1093/eurheartj/ehaf523 - HTML page: https://drgezhang.com/papers/doi-10-1093-eurheartj-ehaf523.html - Google Scholar query: https://scholar.google.com/scholar?q=%22The%20macrophage-derived%20motor%20protein%20KIF13B%20enhances%20MERTK-mediated%20efferocytosis%20and%20prevents%20atherosclerosis%20in%20mice%22 - ORCID: https://orcid.org/0000-0002-3116-3246