Structure-activity relationships of chromogranin A in cell adhesion - Identification of an adhesion site for fibroblasts and smooth muscle cells

Previous studies showed that chromogranin A (CgA), a glycoprotein stored an d co-released with various hormones by neuroendocrine cells and neurons, ca n modulate cell adhesion. We have investigated the structure-activity relat ionships of CgA using fibroblasts and coronary artery smooth muscle cells i n adhesion assays. A recombinant CgA fragment 1-78 and a peptide 7-57 conta ining reduced and alkylated cysteines (Cys(17) and Cys(38)) induced cell ad hesion after adsorption onto solid phases at 50-100 nM. Peptides lacking th e disulfide loop region, including residues 47-68, 39-59, and 39-68, induce d cell adhesion, either bound to solid phases at 200-400 nM or added to the liquid phase at 5-10 mu M, whereas peptide 60-68 was inactive, suggesting that residues 47-57 are important for activity. The effect of CgA-(1-78) wa s blocked by anti-CgA antibodies against epitopes including residues Arg(53 ), His(54), and Leu(57). Substitutions of residues His(54) Gln(55), and Asn (56) with alanine decreased the cell adhesion activity of peptide 47-68. Th ese results suggest that the region 47-57 (RILSILRHQNL) contains a cell adh esion site and that the disulfide bridge is not necessary for the proadhesi ve activity. The ability of soluble peptides to elicit proadhesive effects suggests an indirect mechanism. The high sequence conservation and accessib ility to antibodies suggest that this region is important for the physiolog ical role of CgA.