Type IV collagen is one of the major components of basement membranes, along with laminin and proteoglycans. Both structural and functional abnormalities of these basement membrane components are associated with diabetes mellitus. For example, hyperglycemia causes increased levels of nonenzymatic glycation of basement membranes. Non-enzymatic glycation reduces the affinity of heparin-type IV collagen binding, and the cooperative binding of heparin-type IV collagen with laminin or fibronectin. We will chemically synthesize triple-helical and non-triple-helical peptides from type. IV collagen which (a) bind heparin and (b) promote cell adhesion and migration. Peptides will be both glycated and non-glycated, and incorporate postranslationally modified amino acids such as hydroxyproline (Hyp) and hydroxylysine (Hyl), and mono- and disaccharide-modified Hyl. Using these peptides, we will determine how levels of non-enzymatic glycation, primary amino acid sequence, and protein secondary structure affect the affinity and specificity of heparin and cell binding, and the cooperative binding of heparin with laminin or fibronectin. These studies will help to better define the functional changes that occur in basement membranes following non-enzymatic glycation, and may influence the development of triple-helical peptides as new therapeutic agents.
