Bidirectional signaling between sarcoglycans and the integrin adhesion system in cultured L6 myocytes.
The rat L6 skeletal muscle cell line was used to study expression of the dystrophin-containing glycoprotein complex and its interaction with the integrin system involved in the cell-matrix adhesion reaction. A complex of dystrophin and its associated proteins was fully expressed in L6 myotubes, from which anti-dystrophin or anti-alpha-sarcoglycan co-precipitated integrin alpha 5 beta 1 and other focal adhesion-associated proteins vinculin, talin, paxillin, and focal adhesion kinase. Immunostaining and confocal microscopy revealed that dystrophin, alpha-sarcoglycan, integrin alpha 5 beta 1, and vinculin exhibited overlapping distribution in the sarcolemma, especially at focal adhesion-like, spotty structures. Adhesion of cells to fibronectin- or collagen type I-coated dishes resulted in induction of tyrosine phosphorylation of alpha- and gamma-sarcoglycans but not beta-sarcoglycan. The same proteins were also tyrosine-phosphorylated when L6 cells in suspension were exposed to Arg-Gly-Asp-Ser peptide. All of these tyrosine phosphorylations were inhibited by herbimycin A. On the other hand, treatment of L6 myotubes with alpha- and gamma-sarcoglycan antisense oligodeoxynucleotides resulted in complete disappearance of alpha- and gamma-sarcoglycans and in significant reduction of levels of the associated focal adhesion proteins, which caused about 50% reduction of cell adhesion. These results indicate the existence of bidirectional communication between the dystrophin-containing complex and the integrin adhesion system in cultured L6 myocytes.
Yoshida
T
T
Department of Molecular Physiology, National Cardiovascular Center Research Institute, Osaka, Japan.
Pan
Y
Y
Hanada
H
H
Iwata
Y
Y
Shigekawa
M
M
D000818:Animals; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D016189:Dystrophin / Q000378:metabolism*; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D019012:Integrin beta1 / Q000378:metabolism*; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D018613:Microscopy, Confocal; D018482:Muscle, Skeletal / Q000166:cytology*; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D049031:Sarcoglycans; D014443:Tyrosine / Q000378:metabolism; D016596:Vinculin / Q000378:metabolism
D015815:Cell Adhesion Molecules; D003598:Cytoskeletal Proteins; D016189:Dystrophin; D019012:Integrin beta1; D046911:Macromolecular Substances; D008562:Membrane Glycoproteins; D016376:Oligonucleotides, Antisense; D049031:Sarcoglycans; D016596:Vinculin; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496052:Ptk2 protein, rat