Bryostatin 1 induces biphasic activation of protein kinase D in intact cells.
Bryostatin 1 and phorbol esters are both potent activators of protein kinase C (PKC), although their specific biological effects can differ in many systems. Here, we report that bryostatin 1 activates protein kinase D ( PKD), a novel serine/threonine protein kinase, in intact Swiss 3T3 cells and secondary mouse embryo fibroblasts and in COS-7 cells transiently transfected with a PKD expression construct. The dose response of PKD activation induced by bryostatin 1 follows a striking biphasic pattern with maximal activation achieved at a concentration of 10 nM. Higher concentrations of bryostatin 1 (100 nM) reduced PKD activation induced by phorbol 12,13-dibutyrate to levels stimulated by bryostatin 1 alone. Bryostatin 1-induced PKD activation was markedly attenuated by treatment of cells with the PKC inhibitors bisindolylmaleimide I and Ro 31-8220. However, these agents did not inhibit PKD activity when added directly to in vitro kinase assays, suggesting that bryostatin 1 stimulates PKD activation through a PKC-dependent pathway in intact cells. Our results raise the possibility that activated PKD in intact cells could mediate some of the multiple biphasic biological responses induced by bryostatin 1.[1]References
- Bryostatin 1 induces biphasic activation of protein kinase D in intact cells. Matthews, S.A., Pettit, G.R., Rozengurt, E. J. Biol. Chem. (1997) [Pubmed]
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