INTERACTIONS OF TYPE-IV COLLAGEN AND ITS DOMAINS WITH HUMAN MESANGIALCELLS

Type TV collagen (COL-M interacts with a variety of cell types, We pre sent evidence that human mesangial cells (HMC) bind directly to COL-IV , its major triple helical domain, and the main non-collagenous, NC1 d omain, A synthetic peptide, REP-Ill, and its triple helical counterpar t (TRP-III), previously reported to be a heparin-binding domain, also promoted approximate to 15% adhesion of HMC. HMC bound to solid-phase- immobilized, intact COL-IV (approximate to 75%), isolated NC1 domain ( approximate to 15%), and a pepsin-derived triple helical fragment,whic h lacks Hep-III (approximate to 65%). We further examined inhibition o f HMC adhesion to COL-TV and its domains by using anti-integrin antibo dies. Blocking monoclonal antibodies against the alpha(2) integrin res ulted in 70% inhibition of adhesion to COL-IV and 80% inhibition to HE P-III, Moderate inhibition was observed on the NC1 and triple helical fragments. Anti-alpha(1) antibodies inhibited the binding of HMC to CO L-IV, the NC1, and triple helical domains, but not to peptide HEP-III. Anti-beta(1) antibodies inhibited almost completely (>95%) the adhesi on to COL-IV, the NC1, and triple helical fragments; inhibition on HEP -III was approximate to 30%. Affinity chromatography studies with soli d-phase HEP-III and mesangial cell lysate also demonstrated the presen ce of integrin alpha(2) beta(1) along with alpha(3) beta(1). We conclu de that alpha(2) beta(1) and alpha(1) beta(1) integrins mediate HMC ad hesion to COL-IV. Peptide HEP-III is a major, specific site for alpha( 2) integrin-mediated binding of mesangial cells to COL-IV. Both the al pha(2) beta(1) and alpha(1) beta(1) integrins interact with the NC1 an d triple helical fragments of COL-IV, Therefore, we demonstrate that s everal sites for integrin-mediated interactions exist on several colla genous and non-collagenous domains of COL-IV.