TMEM16A and myocardin form a positive feedback loop that is disrupted by KLF5 during Ang II-induced vascular...

Area of Science:

• Cardiovascular Biology
• Molecular Cell Biology
• Vascular Physiology

Background:

• TMEM16A (Anoctamin-1) is a Ca(2+)-dependent Cl(-) channel (CaCC) crucial in vascular smooth muscle cells (VSMCs).
• TMEM16A has been shown to inhibit angiotensin II-induced proliferation in rat basilar smooth muscle cells.
• The precise role of TMEM16A in vascular remodeling, particularly VSMC proliferation, remains incompletely understood.

Purpose of the Study:

• To elucidate the regulatory mechanism of TMEM16A expression in human aortic smooth muscle cells (HASMCs).
• To investigate the role of the myocardin-SRF complex and Angiotensin II/KLF5 in regulating TMEM16A.
• To explore the therapeutic potential of targeting the TMEM16A feedback loop in vascular remodeling.

Main Methods:

• Luciferase reporter assays to assess promoter activity.
• Western blotting and qRT-PCR to measure protein and gene expression.
• In vivo studies using angiotensin II infusion in mice, including KLF5 null models.

Main Results:

• Myocardin and SRF form a complex that binds the TMEM16A promoter, upregulating TMEM16A expression.
• Upregulated TMEM16A promotes myocardin and VSMC marker gene expression, creating a positive feedback loop that inhibits proliferation.
• Angiotensin II induces KLF5, which disrupts the myocardin-SRF complex, suppresses TMEM16A transcription, and promotes vascular remodeling, an effect blunted in KLF5(-/-) mice.

Conclusions:

• A novel positive feedback loop involving myocardin and TMEM16A regulates VSMC differentiation and proliferation.
• Angiotensin II-induced vascular remodeling is mediated by KLF5-dependent suppression of TMEM16A.
• Disrupting the myocardin-TMEM16A positive feedback loop presents a potential therapeutic strategy for vascular remodeling.