AIMTo investigate the molecular mechanisms of smooth muscle 22 alpha (SM22alpha) whereby cytoskeleton remodeling of vascular smooth muscle cells (VSMCs) is regulated.

METHODSSynthetic (dedifferentiated) VSMCs were converted to contractile (differentiated) VSMCs by serum deprivation. Cells were transfected with pEGFP-SM22alpha, and localization of SM22alpha and its relationship with F-actin were observed through fluorescence microscopy. Fractional extraction of proteins and Western blotting were used to detect polymerization of SM alpha-actin in antisense-pcD2-SM22alpha-transfected VSMCs.Furthermore, effect of SM22alpha on F-actin cross-linking was observed by F-actin polymerization experiment.

RESULTSFluorescence microscopy showed that SM22alpha co-localized with F-actin in contractile VSMCs. Western blotting of protein extracts from F-/G-actin fractions revealed that polymerization of SM alpha-actin was lower in antisense-pcD2-SM22alpha-transfected VSMCs, in which SM alpha-actin mostly existed as soluble G-actin. Moreover, F-actin polymerization in vitro also showed that GST-SM22alpha could promote cross-linking of F-actin to form thick and bundled stress fibres,while extracts from VSMCs transfected with antisense-pcD2-SM22alpha could not effectively induce the polymerization of F-actin.

CONCLUSIONSM22alpha acts as a modulator to participate in VSMC cytoskeleton remodeling. It can not only induce polymerization of G-actin to F-actin, but also promote cross-linking of F-actin to bundled stress fibres, indicating its vital role in cytoskeleton remodeling.