Identification of a novel calcium-binding protein (CP22 ) in multidrug-resistant murine and hamster cells

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Abstract
Analysis of cytoplasmic extracts of multidrug-resistant murine and hamster cells by SDS gel and 2D gel electrophoresis showed that they expressed an abundant 22 kDa protein which was absent from the drugsensitive parent lines. SDS gel electrophoresis in the presence of EGTA and direct binding tests with 45Ca2+ showed that the resistance-associated protein is a specific calcium-binding protein. Thus the development of multidrug resistance in both colchicine-selected hamster cells and adriamycin-selected murine cells is associated with a major change in calcium metabolism. These observations provide the first molecular basis for the hypothesis that Ca2+ plays a central role in the development of the multidrug resistance phenomenon.