Macrophage SR-BI modulates autophagy via VPS34 complex and PPARα transcription of Tfeb in atherosclerosis
Huan Tao, Patricia G. Yancey, John L. Blakemore, Youmin Zhang, Lei Ding, W. Gray Jerome, Jonathan D. Brown, Kasey C. Vickers, MacRae F. Linton
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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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 10

Impact of Tfeb on transcription of VPS34.

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Impact of Tfeb on transcription of VPS34. (A) Knockdown of TFEB by siRNA...
(A) Knockdown of TFEB by siRNA attenuates Vps34 gene expression. J774A.1 macrophages were transfected with 25 nM Tfeb siRNA for 24 hours, and then treated with FC for 24 hours. The expression levels of mRNA encoding TFEB, VPS34, Rab7, and LC3 were detected by real-time PCR. Real-time PCR data are expressed as mean ± SEM from 3 independent experiments (n = 3 per group). *P < 0.05 by unpaired Student’s t test. (B) The potential TFEB binding sites in the Vps34 gene promoter and 5′ UTR were analyzed by in silico methodology, and 2 potential sites were revealed (sites I and II) in the 5′ UTR. (C) TFEB protein interacts with Vps34 gene DNA. The specific DNA oligonucleotides (site I) were labeled with IRDy700. TFEB protein (5 μg) and 1 μL of 25 nM dsDNA were incubated in EMSA buffer for 20 minutes, and then resolved by 5% TBE polyacrylamide gel electrophoresis and the image was captured by LI-COR Odyssey.