Mallia C M, Smith M, Clejan S, Beckman B S
Department of Pharmacology, Tulane University School of Medicine, New Orleans, LA 70112, USA.
J Lipid Mediat Cell Signal. 1997 Dec;17(3):135-50. doi: 10.1016/s0929-7855(97)00027-8.
Erythropoietin (EPO) is a hormone, as well as a hematopoietic growth factor, that specifically regulates the proliferation and differentiation 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 A2, C, and D. A cascade of serine and threonine kinases, including Raf-1, MAP kinase and protein kinase C (PKC) is activated following tyrosine phosphorylation. In this study, we have examined whether changes in nuclear PKC and 1,2-diacylglycerol (DAG) are induced following EPO treatment of the murine target cell line, B6SUt.EP. Western blot analysis using isoform-specific antibodies demonstrated the presence of PKC beta II, but not PKC alpha, beta I, gamma, epsilon, delta, eta, or zeta in the nuclei of cells stimulated with EPO. The increase in nuclear beta II levels was accompanied by an immediate rise in DAG mass levels with both of the increases peaking by 1 min. These rapid increases in nuclear DAG and PKC beta II expression suggest a mechanism for EPO-induced changes in gene expression necessary for cell proliferation.
促红细胞生成素（EPO）是一种激素，也是一种造血生长因子，它特异性地调节红系祖细胞的增殖和分化。尽管EPO的膜结合受体没有内在的激酶活性，但它通过磷脂酶A2、C和D触发蛋白激酶的激活。在酪氨酸磷酸化后，包括Raf-1、丝裂原活化蛋白激酶（MAP激酶）和蛋白激酶C（PKC）在内的一系列丝氨酸和苏氨酸激酶被激活。在本研究中，我们检测了用EPO处理小鼠靶细胞系B6SUt.EP后，细胞核内PKC和1,2-二酰甘油（DAG）是否会发生变化。使用亚型特异性抗体进行的蛋白质印迹分析表明，在用EPO刺激的细胞的细胞核中存在PKCβII，但不存在PKCα、βI、γ、ε、δ、η或ζ。细胞核βII水平的增加伴随着DAG质量水平的立即升高，两者均在1分钟时达到峰值。细胞核DAG和PKCβII表达的这些快速增加表明了一种EPO诱导细胞增殖所需基因表达变化的机制。
