FIBRILLIN - EVIDENCE THAT CHONDROITIN SULFATE PROTEOGLYCANS ARE COMPONENTS OF MICROFIBRILS AND ASSOCIATE WITH NEWLY SYNTHESIZED MONOMERS

We have investigated the potential association of proteoglycans with i ntact fibrillin-containing microfibrils from foetal bovine elastic tis sues and with newly synthesised fibrillin in human and bovine cell cul tures. Microfibril integrity was disrupted by chondroitinase ABC lyase and chondroitinase AC lyase, but not by keratanase or hyaluronidase. Following chondroitinase treatment, beads were disrupted but the under lying fibrillar scaffold appeared intact. Cuprolinic blue was prominen tly associated with beaded domains at a critical electrolyte concentra tion. Electron-dense rods were often associated with cuprolinic blue-t reated microfibrils isolated from fixed tissues. Positive staining rev ealed charged foci at the beads. Newly synthesised fibrillin could be labelled with S-35 TransLabel, [H-3]glucosamine or (SO4)-S-35 but its electrophoretic mobility was not influenced by treatment with chondroi tinase ABC or AC lyase. A diffuse (SO4)-S-35-labelled chondroitinase-s ensitive component with a resistant band (M(r) 35000) co-immunoprecipi tated with fibrillin. These experiments indicate that chondroitin sulp hate proteoglycans associate with fibrillin and contribute to microfib ril assembly, This association has major implications for microfibril function in health and disease.