Ca2+/calmodulin binds and dissociates K-RasB from membrane.

We have investigated the interaction of calmodulin (CaM) with Ras-p21 and the significance of this association. All Ras-p21 isoforms tested (H-, K-, and N-Ras) were detected in the particulate fraction of human platelets and MCF-7 cells, a human breast cancer cell line. In MCF-7 cells, H- and N-Ras were also ...
detected in the cytosolic fraction. K-RasB from platelet and MCF-7 cell lysates was found to bind CaM in a Ca2+ -dependent but GTPgammaS-independent manner. The yeast two-hybrid analysis demonstrated that K-RasB binds to CaM in vivo. Incubation of isolated membranes from platelet and MCF-7 cells with CaM caused dissociation of only K-RasB from membranes in a Ca2+ -dependent manner. CaM antagonist, W7, inhibited dissociation of K-RasB. Addition of platelet or MCF-7 cytosol alone to isolated platelet membranes did not cause dissociation of K-RasB and only addition of exogenous CaM caused dissociation. The results suggest a potential role for Ca2+/CaM in the regulation of K-RasB function.
Mesh Terms:
Blood Platelets, Calcium, Calmodulin, Cell Fractionation, Cell Membrane, Genes, ras, Guanosine 5'-O-(3-Thiotriphosphate), Humans, Protein Binding, Protein Isoforms, Proto-Oncogene Proteins p21(ras), Tumor Cells, Cultured, Two-Hybrid System Techniques
Biochem. Biophys. Res. Commun.
Date: May. 16, 2003
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