The C‐Terminal Domain V of Perlecan Promotes β1 Integrin‐Mediated Cell Adhesion, Binds Heparin, Nidogen and Fibulin‐2 and Can be Modified by Glycosaminoglycans

Open Access
Publisher Website
Google Scholar
Abstract
Domain V of the major basement‐membrane proteoglycan perlecan, a domain which consists of three laminin type G (LG) and four epidermal‐growth‐factor‐like (EG) modules, was obtained in recombinant form by transfecting embryonic kidney cells with an episomal expression vector. A major 90‐kDa fragment V was obtained together with fragments Va (74 kDa) and Vb (26 kDa) which were generated by endogenous proteolysis in front of the most C‐terminal LG module. All three fragments bound to a heparin affinity column and could be displaced at a moderate (0.2 M) NaCl concentration. Rotary‐shadowing electron microscopy demonstrated a three‐globule structure for fragment V. Fragment V also showed a strong immunological cross‐reaction with tissue‐derived perlecan, indicating that it was folded into a native structure. A further, larger fragment, Vc, was apparently substituted with heparan sulphate and/or chondroitin sulphate chains and failed to bind to heparin. Fragment V but not fragment Vc promoted a distinct adhesion of several cell lines and this could be blocked by antibodies against the integrin β1 chain. This domain may, however, represent only one of several cell‐adhesive sites of perlecan. The recombinant perlecan fragment V bound in surface plasmon resonance assays to fibulin‐2, laminin‐nidogen complex, nidogen and two nidogen fragments. This indicated two different nidogen‐binding epitopes on perlecan domain V with about a 10‐fold difference in their affinities (Kd= 0.05–0.2 μM and about 2 μM). Perlecan domain V therefore seems to participate in the supramolecular assembly and cell connections of basement membranes.

This publication has 50 references indexed in Scilit: