Utrophin, the autosomal dystrophin-related protein (DRP), is expressed in HeLa cells, smooth muscle-like BC3HI cells from mouse brain, COS monkey kidney cells, the P38BD1 monocyte-macrophage cell line and untransformed human skin fibroblasts, as well as in rat C6 glioma and Schwannoma cells. It was undetectable, however, in the Sp2/O mouse myeloma cell line and in hybridoma lines derived from it. Dystrophin was not detected in any of these cell lines. Although all utrophin-containing cells were capable of forming monolayers in culture, no major effects of either attachment to substratum or length of time in culture (2–17 days) on utrophin levels were observed. After subcellular fractionation ofBC3HI or glioma cells, nearly all of the utrophin was found in the Triton-soluble fraction, suggesting an association with cell membranes.
