The sarcoglycan complex consists of four membrane-spanning proteins and was
shown to be exclusively distributed in striated muscles. In this study, we
analyzed the pattern of expression of the mRNAs and proteins of the sarcog
lycan subunits during cell differentiation in a culture of myocytes. All fo
ur sarcoglycan mRNAs were detectable in proliferating cells, and expression
of the alpha- and gamma-subunits was up-regulated by 20- and 50-fold follo
wing muscle cell fusion. However, sarcoglycan proteins were scarcely detect
able in proliferating cells and were first detected 2 days after the induct
ion to be differentiated. The accumulation of the sarcoglycan protein subun
its was accompanied by cell differentiation. The discrepancy between the ex
pression of the mRNAs and proteins of the sarcoglycan subunits in prolifera
ting cells may be ascribed to rapid degradation of the protein. (C) 1999 Ac
ademic Press.