Macrophage SR-BI modulates autophagy via VPS34 complex and PPARα transcription of Tfeb in atherosclerosis
Huan Tao, … , Kasey C. Vickers, MacRae F. Linton
Huan Tao, … , Kasey C. Vickers, MacRae F. Linton
Published March 4, 2021
Citation Information: J Clin Invest. 2021;131(7):e94229. https://doi.org/10.1172/JCI94229.
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Research Article Cardiology Vascular biology

Macrophage SR-BI modulates autophagy via VPS34 complex and PPARα transcription of Tfeb in atherosclerosis

Abstract

Autophagy modulates lipid turnover, cell survival, inflammation, and atherogenesis. Scavenger receptor class B type I (SR-BI) plays a crucial role in lysosome function. Here, we demonstrate that SR-BI regulates autophagy in atherosclerosis. SR-BI deletion attenuated lipid-induced expression of autophagy mediators in macrophages and atherosclerotic aortas. Consequently, SR-BI deletion resulted in 1.8- and 2.5-fold increases in foam cell formation and apoptosis, respectively, and increased oxidized LDL–induced inflammatory cytokine expression. Pharmacological activation of autophagy failed to reduce lipid content or apoptosis in Sr-b1–/– macrophages. SR-BI deletion reduced both basal and inducible levels of transcription factor EB (TFEB), a master regulator of autophagy, causing decreased expression of autophagy genes encoding VPS34 and Beclin-1. Notably, SR-BI regulated Tfeb expression by enhancing PPARα activation. Moreover, intracellular macrophage SR-BI localized to autophagosomes, where it formed cholesterol domains resulting in enhanced association of Barkor and recruitment of the VPS34–Beclin-1 complex. Thus, SR-BI deficiency led to lower VPS34 activity in macrophages and in atherosclerotic aortic tissues. Overexpression of Tfeb or Vps34 rescued the defective autophagy in Sr-b1–/– macrophages. Taken together, our results show that macrophage SR-BI regulates autophagy via Tfeb expression and recruitment of the VPS34–Beclin-1 complex, thus identifying previously unrecognized roles for SR-BI and potentially novel targets for the treatment of atherosclerosis.

Authors

Huan Tao, Patricia G. Yancey, John L. Blakemore, Youmin Zhang, Lei Ding, W. Gray Jerome, Jonathan D. Brown, Kasey C. Vickers, MacRae F. Linton

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Figure 5

Hematopoietic SR-BI deletion leads to attenuated autophagy in atherosclerotic lesions.

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Hematopoietic SR-BI deletion leads to attenuated autophagy in atheroscle...
(A) Total RNA was isolated from the aortic arches of Ldlr–/– mice transplanted with WT or Sr-b1–/– bone marrow and fed either a chow or Western diet for 16 weeks. Relative gene expression was analyzed by real-time qPCR. Data are presented as mean ± SEM (n = 3 mice per group). *P < 0.05, **P < 0.01 by 1-way ANOVA with Bonferroni’s post hoc test. (B and C) Ldlr–/– mice were reconstituted with WT, Sr-b1–/–, Apoe–/–, and Sr-b1–/– Apoe–/– (DKO) bone marrow and fed a Western diet for 16 weeks. (B) Proximal aortic sections were stained using anti–Beclin-1 primary antibody and FITC-labeled secondary antibody (green). Nuclei were counterstained with Hoechst (blue). Scale bar: 100 μm. (C) Beclin-1–positive area and total lesion area were quantitated by ImageJ software. (D and E) Apoe–/– mice were reconstituted with Apoe–/– or DKO bone barrow and fed a Western diet for 8 weeks. (D) Proximal aortic sections were immunofluorescently stained with anti-LC3II primary antibody and Alexa Fluor 568–labeled secondary antibody (red). Nuclei were counterstained with Hoechst (blue). Scale bar: 100 μm. (E) LC3II-positive area and total lesion area were quantified by ImageJ software. (B–E) Data are presented as mean ± SEM (n = 6 mice per group). ***P < 0.001 by 1-way ANOVA with Bonferroni’s post hoc test (C) and *P < 0.05 by Mann-Whitney test (E).