Components of the Protein Synthesis and Folding Machinery Are Induced in Vascular Smooth Muscle Cells by Hypertrophic and Hyperplastic Agents: IDENTIFICATION BY COMPARATIVE PROTEIN PHENOTYPING AND MICROSEQUENCING

Abstract

Vascular smooth muscle cells (VSMC) are the principal cellular component of the blood vessel wall. Atherosclerosis, hypertension, and angiogenesis are associated with abnormal VSMC growth. Angiotensin II is hypertrophic for cultured adult rat aortic VSMC, whereas platelet-derived growth factor and serum are hyperplastic. To identify changes in specific proteins associated with either hyperplastic or hypertrophic growth, high resolution two-dimensional gel electrophoresis was performed on extracts from quiescent rat aortic VSMC and from VSMC exposed for 24 h to growth factors (10% fetal calf serum, platelet-derived growth factor, or angiotensin II). 12 proteins were up-regulated and 5 down-regulated by treatment with growth factors. Eight of the up-regulated and one of the down-regulated proteins were identified by internal protein microsequencing from electroblotted two-dimensional gels or by co-electrophoresis of purified proteins in two-dimensional gels. Four of the proteins up-regulated by growth factors were identified as mediators of protein folding. These were heat shock proteins, HSP-60 and HSP-70, protein disulfide isomerase, and protein disulfide isomerase isozyme Q-2. Additional proteins were identified as elongation factor EF-1 beta, a component of the protein synthesis apparatus, and calreticulin, another putative molecular chaperone. Vimentin and actin were also up-regulated, whereas an isoform of myosin heavy chain was down-regulated. Hyperplastic and hypertrophic growth were accompanied by similar changes in protein expression, suggesting that both types of growth require up-regulation of the protein synthesis and folding machinery.