The beta-delta-core of sarcoglycan is essential for deposition at the plasma membrane.
Mutations of any of the sarcoglycan complex subunits (alpha, beta, delta, and gamma) cause limb-girdle muscular dystrophy. Furthermore, individual mutations lead to a reduction or loss of all other members of the complex. In some cases of limb-girdle muscular dystrophies, however, residual sarcoglycan expression has been documented. Therefore, in this study we tested the hypothesis that formation of specific sarcoglycan subcomplexes is crucial for plasma membrane deposition. Using co-immunoprecipitation assays, we demonstrated that beta- and delta-sarcoglycan interact with alpha-sarcoglycan and these two subunits must be co-expressed for export from the endoplasmic reticulum. Advanced light-microscopic imaging techniques demonstrated that co-expression of beta-sarcoglycan and delta-sarcoglycan is also responsible for delivery to and retention of sarcoglycan subcomplexes at the cell surface. These data suggest that formation of the beta-delta-core may promote the export and deposition of sarcoglycan subcomplexes at the plasma membrane, and therefore identifies a mechanism for sarcoglycan transport.
Draviam
Romesh A
RA
Department of Cell Biology and Molecular Physiology, University of Pittsburgh School of Medicine, S224 Biomedical Science Tower, 3500 Terrace Street, Pittsburgh, Pennsylvania 15261, USA.
Shand
Stuart H
SH
Watkins
Simon C
SC
D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D002478:Cells, Cultured; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D006801:Humans; D047468:Immunoprecipitation; D021381:Protein Transport; D049031:Sarcoglycans / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D021601:trans-Golgi Network / Q000737:chemistry / Q000378:metabolism
C483098:SGCB protein, human; D049031:Sarcoglycans; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins