An RBPMS-driven splicing regulatory axis including MBNL1, RBFOX2, and QK promotes smooth muscle cell contractile...

Area of Science:

• Molecular Biology
• Cell Biology
• Cardiovascular Research

Background:

• Vascular smooth muscle cell (SMC) phenotype switching between contractile and proliferative states is a hallmark of cardiovascular disease.
• Alternative splicing (AS) programs, regulated by RNA-binding proteins (RBPs), are critical drivers of these phenotypic changes.
• RNA Binding Protein with Multiple Splicing (RBPMS) was previously identified as a master regulator of AS in differentiated SMCs.

Purpose of the Study:

• To investigate the roles of MBNL1, RBFOX2, and QK as coregulators with RBPMS in SMC AS and phenotype.
• To understand how these RBPs collectively maintain the contractile SMC phenotype.

Main Methods:

• Investigated the function of RBPMS, MBNL1, RBFOX2, and QK in SMCs.
• Utilized knockdown experiments to assess the impact of each RBP on SMC phenotype and AS.
• Analyzed splicing events enriched for functions related to actin filaments and focal adhesions.

Main Results:

• All four RBPs (RBPMS, MBNL1, RBFOX2, QK) generally promoted contractile SMC splicing, with RBPMS showing the strongest alignment.
• Coregulated splicing events were associated with actin filaments and focal adhesions, suggesting coordinated remodeling of the contractile machinery.
• Knockdown of RBPMS alone induced all aspects of phenotype switching (reduced contraction, increased proliferation, and motility), while individual knockdowns of other RBPs had varied effects.

Conclusions:

• RBPMS acts as a master regulator, guiding other RBPs to control SMC phenotype switching independently of transcriptional programs.
• This RBP network is crucial for maintaining SMC contractile function and preventing disease-associated phenotypic transitions.
• The findings reveal a coordinated regulatory axis by RBPs in driving fundamental cellular phenotype changes.