Apolipoprotein A-1 expression is resistant to dimethyl sulfoxide inhibition of myogenic differentiation.
Primary cultures of chick embryonic muscle (CEM) were analyzed for the differential expression of a 26-kDa protein during myogenesis. We have identified this 26-kDa protein as apolipoprotein A-1 (Apo A-1), the major protein of serum high density lipoprotein particles. Apo A-1 was expressed in a pattern temporally similar to those of muscle-specific proteins, by myoblasts at very low levels, and by myotubes at high levels. The half-life of Apo A-1 in CEM cell homogenates was 23 min. This fast turnover rate appeared to be due to the secretion of Apo A-1 into the culture medium. To further characterize the relationship of Apo A-1 expression and myogenic differentiation, CEM cultures were treated with dimethyl sulfoxide (DMSO). In the presence of 2% DMSO, myotubes exhibited an atrophied morphology and an inhibition of the synthesis and accumulation of muscle-specific sarcomeric proteins. During recovery from DMSO treatment, the expression and accumulation of muscle-specific proteins returned to high levels. In contrast, the rates of synthesis and secretion of Apo A-1 in control, DMSO-treated, and DMSO-recovered CEM cells were nearly equivalent. These results indicate that the expression of Apo A-1 is not strictly linked to the expression of muscle-specific sarcomeric proteins in skeletal muscle and suggest that independent, or additional regulatory mechanisms exist which modulate Apo A-1 expression during myogenesis.
Department of Biology, University of Iowa, Iowa City 52242.
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D000818:Animals; D016632:Apolipoprotein A-I / Q000096:biosynthesis* / Q000235:genetics; D015153:Blotting, Western; D002454:Cell Differentiation / Q000187:drug effects; D002478:Cells, Cultured; D002642:Chick Embryo; D004121:Dimethyl Sulfoxide / Q000494:pharmacology*; D004351:Drug Resistance; D015180:Electrophoresis, Gel, Two-Dimensional; D005786:Gene Expression Regulation; D006207:Half-Life; D008855:Microscopy, Electron, Scanning; D009132:Muscles / Q000166:cytology / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D014176:Protein Biosynthesis
D016632:Apolipoprotein A-I; D004121:Dimethyl Sulfoxide