The macromolecular associations of heat shock protein-27 in vascular smooth muscle

Background. Behavioral stress is a risk factor for hypertension and atherosclerosis. Stress leads to increases in the expression and phosphorylation of heat shock proteins (HSPs) in vascular smooth mss cb. Two small heat shock proteins, HSP27 and HSP20, have been implicated in the regulation of the contraction and relaxation of smooth muscle. We hypothesized that stress-induced alterations in the phosphorylation of HSP27 would effect the macromolecular associations of the small HSPs. Methods. Bovine carotid artery smooth muscle was treated with buffer alone or with the chemical stressor; arsenite. HSP27 phosphorylation was determined with isoelectric focusing immunoblotting Macromolecular interactions were determined with subcellular fractionation, molecular sieving, and glutaraldehyde cross-linking and immunoblotting. Results. Arsenite treatment led to increases in the phosphorylation of HSP27, a redistribution of some HSP27 from a cytosolic to a particulate fraction and to the formation of larger macromolecular aggregates of HSP27. Glutaraldehyde cross-linking and immunoblotting demonstrated that HSP27 existed in monomeric and dimeric forms, which suggested that the large aggregates were not simply aggregates of HSP27 but contained other proteins. Conclusions. Cellular stress leads to increases in the phosphorylation of HSP27 and to changes in the macromolecular associations of HSP27 in intact vascular smooth muscles. The functions of the small HSPs in the vascular smooth muscle may be dependent on both phosphorylation and macromolecular associations.