title: Binding of soluble type I collagen to fibroblasts: effects of thermal activation of ligand, ligand concentration, pinocytosis, and cytoskeletal modifiers.
abstract: Efficient binding of native, soluble 125I-labeled type I rat collagen to mouse 3T3 fibroblast monolayers requires prior warming of the ligand to 35-37 degrees C for 10-30 min. Decreased binding at high ligand concentrations is ascribed to ligand-ligand interactions rather than to negative cooperativity. Addition of bacterial collagenase to monolayers labeled with the 125I-ligand releases a constant fraction (80%) of the bound ligand over a 2-h interval at 37 degrees C, indicating that little of the ligand becomes inaccessible by pinocytosis. Colchicine (10(-7) M) and vinblastine (5 X 10(-8) M) do not inhibit binding by morphologically intact monolayers. Cytochalasins and concanavalin A show dose-related inhibition of binding by intact monolayers that is due to a reduction in the number of available binding sites rather than to a change in binding site affinity. The collagen binding site on the fibroblast surface is proposed as an organizing center for the assembly of periodic type I collagen fibrils.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D003078:Colchicine / Q000494:pharmacology; D003094:Collagen / Q000378:metabolism*; D003208:Concanavalin A / Q000494:pharmacology*; D003572:Cytochalasins / Q000494:pharmacology*; D005347:Fibroblasts; D006358:Hot Temperature; D051379:Mice; D010873:Pinocytosis; D011487:Protein Conformation; D014747:Vinblastine / Q000494:pharmacology
chemical_list: D003572:Cytochalasins; D003208:Concanavalin A; D014747:Vinblastine; D003094:Collagen; D003078:Colchicine