Involvement of Protein Phosphorylation in the Degranulation from Rat Basophilic Leukemia Cells

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In this study,we inverstigate the inhibitory mechanism of various cytochalasins on the serotonin release from RBL-2H3 cells. All cytochalasins which inbibit the serotonin release suppressed the protein kinase C activity and the phosphorylation of 36 kDa membrenous protein. On the other hand, cytochalasins which engance the release did not inhibit the protein kinase C and the phosphorylation of 36 kDa protein.Enhancement of the phosphorylation of 18 kDa protein was also observed by the antigen (DNP-BSA) stimulation. The phosphorylation of this protein was Ca^<2+>-dependent. The phosphorylated protein was precipitated with actomyosin and behave as a myosin light chain.we,furthermore,studied the effect of various drugs on the degranulation from RBL-2H3 cells. phosphoinosiitdes (PI) turnover and diacylglycerol (DG) formation were enganced by the antigen stimulation. However,when the formation of DG was inhibited by neomycin,the serotonin release was suppressed in proportion to the degree of the inhibition of DG formation. All of these results support our concept that the phosphorylation of 36 kDaprotein by protein kinase C is essential for the degranulatuion from RBL-2H3 cells