Interaction of skeletal muscle cells with collagen type IV is mediated by perlecan associated with the cell surface

We have previously shown that the expression of perlecan, a heparan sulfate proteoglycan localized on the myoblast surface, is down-regulated during t erminal differentiation of skeletal muscle myoblasts (Larrain et al. [1997] Exp. Cell Res. 234:405-412). In this study, we have evaluated the biochemi cal characteristics of perlecan, its association with the myoblast surface, and its involvement in C2C12 myoblast adhesion to different substrates. Pe rlecan associated with myoblasts was solubilized by Triton X-100, whereas h eparin, high salt, and RGD peptides were unable to solubilize perlecan. Pre -incubation of myoblasts with [S-35]-Na2SO4, followed by solubilization wit h Triton X-100 and immunoprecipitation with antibodies against murine perle can, demonstrated that this proteoglycan present on the cell surface has a heterogeneous size profile with a K-av value of 0.45, determined by Sepharo se CL-4B chromatography. Myoblasts were found to adhere with decreasing aff inities to collagen type IV, type I, laminin, fibronectin, perlecan, and ma trigel. We found that cell adhesion to collagen type IV was inhibited by bl ocking this substrate with exogenous perlecan prior to cell plating, wherea s no effect was observed for laminin. Furthermore, adhesion of myoblasts to collagen type IV was inhibited by the perlecan core protein obtained by tr eatment of perlecan with heparitinase, as well as by pre-incubation of the cells with antibodies against murine perlecan. These data support the idea that skeletal muscle cells interact with collagen type IV through the perle can core protein present on the surface of undifferentiated myoblasts. (C) 1999 Wiley-Liss, Inc.