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

Background. Behavioral stress is a risk factor for hypertension and atheros clerosis. Stress leads to increases in the expression and phosphorylation o f heat shock proteins (HSPs) in vascular smooth mss cb. Two small heat shoc k proteins, HSP27 and HSP20, have been implicated in the regulation of the contraction and relaxation of smooth muscle. We hypothesized that stress-in duced alterations in the phosphorylation of HSP27 would effect the macromol ecular 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 determin ed with isoelectric focusing immunoblotting Macromolecular interactions wer e determined with subcellular fractionation, molecular sieving, and glutara ldehyde cross-linking and immunoblotting. Results. Arsenite treatment led to increases in the phosphorylation of HSP2 7, a redistribution of some HSP27 from a cytosolic to a particulate fractio n and to the formation of larger macromolecular aggregates of HSP27. Glutar aldehyde cross-linking and immunoblotting demonstrated that HSP27 existed i n monomeric and dimeric forms, which suggested that the large aggregates we re not simply aggregates of HSP27 but contained other proteins. Conclusions. Cellular stress leads to increases in the phosphorylation of H SP27 and to changes in the macromolecular associations of HSP27 in intact v ascular smooth muscles. The functions of the small HSPs in the vascular smo oth muscle may be dependent on both phosphorylation and macromolecular asso ciations.