The overall aim of this project is to fully characterize the monocyte chemoattractant SMC-CF, which is secreted by baboon aortic smooth muscle cells (SMC) and which may regulate the intimal recruitment of blood monocytes in atherogenesis. This potent chemoattractant is associated with a low molecular weight (12-16 kD) basic monomeric protein which has been successfully purified to homogeneity. Baboon SMC express the c-sis gene, which encodes one of the two polypeptide chains of platelet-derived growth factor (PDGF), a potent mitogen for SMC. PDGF in both its monomeric and dimeric forms is also a potent chemoattractant for monocytes. Preliminary metabolic labeling studies indicate that baboon SMC synthesize and secrete non-mitogenic, monomeric PDGF-like proteins of MW 100 kD and 12 kD. It is possible that SMC-CF and PDGF-like protein are related.
The aim of these studies is to determine the primary amino acid sequence of SMC-CF, by determining the nucleotide sequencing of SMC-CF cDNA and compare it with the published sequence of PDGF and other proteins for homology. A polyclonal antiserum to SMC-CF will be developed for use in determining structural similarity between SMC-CF and PDGF and other chemoattractants. In addition, antibodies to PDGF and PDGF-related peptides provided by Drs. Antoniades and Graves will be used. Receptor studies will be carried out to characterize the binding of SMC-CF to monocytes. The functional similarity between SMC-CF, PDGF and other chemoattractants will be determined by competition for receptor sites. The intracellular processing pathways of both SMC-CF and PDGF-like proteins will be established in the SMC utilizing immunoprecipitation techniques. The influence of SMC phenotype on SMC-CF secretion, c-sis expression and the synthesis of PDGF-like proteins will also be examined. These proposed studies will provide basic biologic insights into the mechanism whereby SMC might regulate monocyte recruitment to the intima in atherogenesis.
