ERYTHROPOIETIN STIMULATES NUCLEAR-LOCALIZATION OF DIACYLGLYCEROL AND PROTEIN-KINASE-C BETA-II IN B6SUT.EP CELLS

Erythropoietin (EPO) is a hormone, as well as a hematopoietic growth f actor, that specifically regulates the proliferation and differentiati on of erythroid progenitor cells. Although the membrane-bound receptor for EPO has no intrinsic kinase activity, it triggers the activation of protein kinases via phospholipases A(2), C, and D. A cascade of ser ine and threonine kinases, including Raf-1, MAP kinase and protein kin ase C (PKC) is activated following tyrosine phosphorylation. In this s tudy, we have examined whether changes in nuclear PKC and 1,2-diacylgl ycerol (DAG) are induced following EPO treatment of the murine target cell line, B6SUt.EP. Western blot analysis using isoform-specific anti bodies demonstrated the presence of PKC beta II, but not PKC alpha, be ta I, gamma, epsilon, delta, eta, or zeta in the nuclei of cells stimu lated with EPO. The increase in nuclear beta II levels was accompanied by an immediate rise in DAG mass levels with both of the increases pe aking by 1 min. These rapid increases in nuclear DAC and PKC beta II e xpression suggest a mechanism for EPO-induccd changes in gene expressi on necessary for cell proliferation. (C) 1997 Elsevier Science B.V.