LC4-5 Domains of Laminin-211 Binds alpha-Dystroglycan to Allow Myotube Attachment and Prevent Anoikis

Poly(2-hydroxyethyl methacrylate) (PolyHEMA) prevents cell attachment was used here to study anoikis, the process where cells die when unattached or attached to an inappropriate matrix, in mouse C2C12 myotubes. A method was developed to efficiently embed proteins into PolyHEMA and the effect on cultured myotubes was determined. Myotubes grown on PolyHEMA-coated plates fail to attach to the surface and remain as rounded, suspended cells, undergo dramatic increases in apoptosis and necrosis, and the number of viable cells decreases. Incorporation of merosin (laminin-211) or the short laminin globular (LG4-5) modules of the laminin-alpha 2 chain C-terminus (called 2E3) that binds a-dystroglycan diminishes both apoptosis and necrosis and increases viability while bovine serum albumin had a much lesser effect, showing the specificity of this effect for these matrix proteins. One sarcolemma receptor for laminin-binding is alpha-dystroglycan. An antibody which binds alpha-dystroglycan but which does not block laminin-binding (VIA4) had little effect on apoptosis or viability on merosin or 2E3 embedded plates while another antibody (IIH6) which specifically blocks binding dramatically decreased viability and increased apoptosis. When merosin or 2E3 are added to culture media rather than embedded on plates these can also increase viability and decrease apoptosis even though the cells remain in suspension, though the effect is not as great as found for the embedded proteins where the cells attach. Thus, we conclude that the binding of a small LG4-5 modules of laminin-211 to alpha-dystroglycan is important in preventing anoikis and that attachment plus binding is necessary for maximal cell survival. J. Cell. Physiol. 222: 111-119, 2010. (C) 2009 Wiley-Liss, Inc.