Oligomerization of beta-dystroglycan in rabbit diaphragm and brain as revealed by chemical crosslinking.
The surface component beta-dystroglycan is a member of the dystrophin-glycoprotein complex providing a trans-sarcolemmal linkage between the actin membrane cytoskeleton and the extracellular matrix component laminin-alpha2. Although abnormalities in this complex are involved in the pathophysiology of various neuromuscular disorders, little is known about the organization of dystrophin-associated glycoproteins in diaphragm and brain. We therefore investigated the oligomerization of beta-dystroglycan and its connection with the most abundant dystrophin homologues in these two tissues. Employing detergent solubilization and alkaline extraction procedures of native membranes, it was confirmed that beta-dystroglycan behaves like an integral surface molecule as predicted by its cDNA sequence. Immunoblot analysis following chemical crosslinking of native membranes showed that beta-dystroglycan has a tendency to form high-molecular-mass complexes. Within these crosslinkable complexes, immuno-reactive overlaps were observed between beta-dystroglycan, alpha-dystroglycan, laminin and 427 kDa dystrophin in diaphragm and skeletal muscle. In synaptosomes, the major brain dystrophin isoform Dp116 also exhibited an immuno-reactive overlap with members of the dystroglycan complex. These findings demonstrate that beta-dystroglycan does not exist as a monomer in native membranes and imply that certain dystrophin isoforms and dystrophin-associated components interact with this surface protein in diaphragm and brain as has been previously shown for skeletal and heart muscle.
Finn
D M
DM
Department of Pharmacology, University College Dublin, Belfield, Dublin 4, Ireland.
Ohlendieck
K
K
D000818:Animals; D001923:Brain Chemistry; D003432:Cross-Linking Reagents / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D003964:Diaphragm / Q000737:chemistry; D049030:Dystroglycans; D016189:Dystrophin / Q000031:analogs & derivatives / Q000378:metabolism; D007797:Laminin / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000737:chemistry; D009206:Myocardium / Q000737:chemistry; D011108:Polymers / Q000378:metabolism*; D011817:Rabbits
D003432:Cross-Linking Reagents; D003598:Cytoskeletal Proteins; D016189:Dystrophin; D007797:Laminin; D008562:Membrane Glycoproteins; D011108:Polymers; D049030:Dystroglycans