Lamellipodia and tail retraction in cell F-actin stained with Acti- Stain™ 488 (Cat. #PHDG1)
Lining blood vessel walls, vascular smooth muscle cells (VSMCs) display a quiescent, contractile phenotype. VSMC contraction and changes in phenotype rely upon regulated actomyosin activity. Mechanical cues (e.g., blood flow-derived stretch and matrix stiffness) stimulate VSMCs to adapt a proliferative synthetic phenotype. Here, the authors examine how the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex, which spans the nuclear envelope and links cytoplasmic F-actin with the nuclear lamina, regulates remodeling of VSMC actin cytoskeleton during actomyosin-mediated force generation. Disruption of the LINC complex in isolated VMSCs by siRNA-mediated loss of SUN1 and SUN2 (members of the nesprin and Sad1p, UNC-84 [SUN]-domain family), two essential components of the complex, results in reduced RhoA activation and actomyosin activity. The authors conclude that RhoA (via ROCK [rho-associated, coiled-coil-containing protein kinase] effector signaling) and SUN1/2 comprise a biophysical circuit which controls actomyosin activity in isolated VSMCs. Cytoskeleton’s RhoA G-LISA activation assay and Total RhoA ELISA kits (Cat. # BK124 and BK150, respectively) were essential in identifying specific changes in RhoA activity, thus demonstrating that RhoA serves as a molecular mediator of actomyosin-mediated morphological and motile changes in VSMCs. Furthermore, a mechano-signaling loop between RhoA and SUN2 in the regulation of actomyosin activity is hypothesized.
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