Protein kinase C translocates from cytosol to membrane upon hormone activation: effects of thyrotropin-releasing hormone in GH3 cells

The subcellular distribution of protein kinase C (PK C) was examined in thyrotropin-releasing hormone (TRH)--responsive GH3 pituitary cells. TRH treatment, which is known to stimulate polyphosphoinositide turnover and diacylglycerol generation, resulted in a rapid (less than or equal to 15 sec) and transient redistribution of the enzyme from cytosol to membrane fraction. Other agents which either stimulate PK C directly (1-oleoyl-2-acetyl-sn-glycerol and 12-O-tetradecanoyl phorbol-13-acetate) or elevate cellular diglyceride levels (phospholipase C) also promoted a redistribution of the enzyme from cytosol to membrane. These results provide evidence for the concept that cell-surface receptor-mediated phosphoinositide breakdown activates PK C. It appears that translocation of PK C to the membrane is an early step in the cellular activation of this enzyme.