Sorbs2 mediates phenotypic plasticity and mechanotransduction in vascular smooth muscle cells

Objective: Sorbs2 has previously been identified as a protein highly expressed in vascular tissues relative to other tissue types. Our goal is to understand the role of Sorbs2 in vascular biology. Hypothesis: Sorbs2 regulates the cytoskeletal dynamics of vascular smooth muscle cells (VSMC) and facilitates VSMC phenotypic plasticity and mechanotransduction. Methods and Results: To test if Sorbs2 regulates VSMC proliferation, three experiments were performed. Immortalized rat SMCs were transfected with control or Sorbs2-siRNA, primary VSMCs from Sorbs2-F/F mice were transduced with Ad5-GFP or Ad5-CRE, or primary VSMCs were isolated from Sorbs2-WT and Sorbs2-KO mice. Primary VSMCs were taken from mice of both sexes. Proliferation was assayed via MTT or Cell Titer Glo. Our data show that Sorbs2-siRNA knockdown reduced SMC cell number ~ 50% after 3 days in culture (n=8, p<0.01). Acute Sorbs2-KO showed decreased proliferation after 48 hours compared to WT (n=6, p<0.01). Sorbs2- global KO SMC showed decreased PDGF-stimulated proliferation over 72 hours (AUC, GFP=118±2.8 vs CRE=97±1.2, n=5) compared to WT. To test if Sorbs2 is involved in VSMC mechanical signaling responses, primary Sorbs2-WT or Sorbs2-KO VSMC were plated on elastic membranes and cultured with or without stretch for 24 hours. After, cells were isolated for protein and RNA expression analysis via western blots (WB), qPCR, and RNAseq. Under static conditions, WB of contractile proteins shows higher expression of Calponin, and MRFT-A in Sorbs2-KO (n=6). qPCR analysis of the same contractile genes shows reduced mRNA expression, suggesting post-transcriptional gene regulation. Stretch increased phosphorylation of ERK1/2, and decreased Sorbs2 expression. RNA sequencing of Sorbs2-KO VSMC vs WT showed an increase in genes involved in VSMC contractility (Z=4.8, p<0.0001) and focal adhesion pathways (Z=5.8, p<0.0001). When these cultures underwent stretch, Sorbs2-KO VSMCs still showed compensatory upregulation of genes associated in focal adhesion (Z=4.9, p<.0001) compared to WT. Conclusion: Our results suggest Sorbs2 is a novel regulator of VSMC phenotypic plasticity and is involved with cellular signaling responses to mechanical stress. We think this is due to its role regulating cytoskeletal stability by regulating focal adhesion protein expression, actin cytoskeletal dynamics, and microtubule stability. Future work will dissect specific molecular interactions between Sorbs2 isoforms’ roles in regulating the phenotypic plasticity of vascular smooth muscle cells. Funding Sources: American Heart Association 23-CDA-1055147 Alzheimer’s Association AARF-22-971256 This abstract was presented at the American Physiology Summit 2025 and is only available in HTML format. There is no downloadable file or PDF version. The Physiology editorial board was not involved in the peer review process.