Cameron M R, Foster J S, Bukovsky A, Wimalasena J
Department of Obstetrics/Gynecology, University of Tennessee Medical Center, Knoxville 37920, USA.
Biol Reprod. 1996 Jul;55(1):111-9. doi: 10.1095/biolreprod55.1.111.
A variety of growth factors and guanosine triphosphate (GTP) binding protein-linked receptors are known to activate mitogen activated protein kinases (MAPK); however, no evidence exists demonstrating activation of the MAPK pathway by glycoprotein hormones. Using porcine granulosa cells (PGC), we show that physiological concentrations of LH and FSH increase enzymatic activity 1) of p44MAPK extracellular regulated kinase 1 (ERK1) but not that of p42MAPK (ERK2) in the cytosol and 2) of both ERK1 and ERK2 in the nucleus. Cytosolic ERK1 was activated by LH more rapidly than by FSH. Cyclic AMP increased kinase activities of both ERK1 and ERK2 in the cytoplasm as well as in the nucleus. Activation of ERK1 by gonadotropins and cAMP was accompanied by increased tyrosine phosphorylation of the kinase. Immunohistochemical studies demonstrated predominantly cytoplasmic staining for MAPK in untreated PGC cultures whereas treatment with gonadotropins led to increased nuclear immunoreactivity indicating translocation of MAPK to the nucleus. The translocation as well as increase in nuclear ERK1 and ERK2 was delayed and coincided with a decrease in cytosolic ERK1 activity. Epidermal growth factor (EGF) increased ERK1 and ERK2-associated kinase activity 7-8-fold in the cytoplasm of PGC, while kinase activity of cytoplasmic ERK1 was enhanced 3-4-fold by LH, FSH, or cAMP. In summary, we have for the first time demonstrated that gonadotropins (and cAMP) can activate MAPK in appropriate target cells.
已知多种生长因子和鸟苷三磷酸（GTP）结合蛋白偶联受体可激活丝裂原活化蛋白激酶（MAPK）；然而，尚无证据表明糖蛋白激素能激活MAPK信号通路。我们利用猪颗粒细胞（PGC）进行研究，结果显示，生理浓度的促黄体生成素（LH）和促卵泡生成素（FSH）可提高1）细胞质中p44MAPK细胞外调节激酶1（ERK1）的酶活性，但不提高p42MAPK（ERK2）的酶活性，以及2）细胞核中ERK1和ERK2的酶活性。细胞质中的ERK1被LH激活的速度比被FSH激活的速度更快。环磷酸腺苷（cAMP）可提高细胞质和细胞核中ERK1和ERK2的激酶活性。促性腺激素和cAMP对ERK1的激活伴随着该激酶酪氨酸磷酸化的增加。免疫组织化学研究表明，未经处理的PGC培养物中MAPK主要呈细胞质染色，而用促性腺激素处理则导致核免疫反应性增加，表明MAPK转位至细胞核。转位以及细胞核中ERK1和ERK2的增加出现延迟，且与细胞质中ERK1活性的降低同时发生。表皮生长因子（EGF）可使PGC细胞质中ERK1和ERK2相关的激酶活性提高7 - 8倍，而LH、FSH或cAMP可使细胞质中ERK1的激酶活性提高3 - 4倍。总之，我们首次证明促性腺激素（和cAMP）可在合适的靶细胞中激活MAPK。
