Matsuda Miho, Hirata Masato
Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan.
Laboratory of Molecular and Cellular Biochemistry, Faculty of Dental Science, Kyushu University, Fukuoka 812-8582, Japan; Fukuoka Dental College, Fukuoka 814-0193, Japan.
J Biol Chem. 2017 May 19;292(20):8369-8380. doi: 10.1074/jbc.M116.759928. Epub 2017 Mar 30.
Phospholipase C-related but catalytically inactive proteins PRIP-1 and -2 are inositol-1,4,5-trisphosphate binding proteins that are encoded by independent genes. Ablation of the genes in mice impairs female fertility, which is manifested by fewer pregnancies, a decreased number of pups, and the decreased and increased secretion of gonadal steroids and gonadotropins, respectively. We investigated the involvement of the PRIPs in fertility, focusing on the ovaries of and double-knock-out (DKO) mice. Multiple cystic follicles were observed in DKO ovaries, and a superovulation assay showed a markedly decreased number of ovulated oocytes. Cumulus-oocyte complexes showed normal expansion, and artificial gonadotropin stimulation regulated the ovulation-related genes in a normal fashion, suggesting that the ovulation itself was probably normal. A histological analysis showed atresia in fewer follicles of the DKO ovaries, particularly in the secondary follicle stages. The expression of luteinizing hormone receptor (LHR) was aberrantly higher in developing follicles, and the phosphorylation of extracellular signal-regulated protein kinase, a downstream target of LH-LHR signaling, was higher in DKO granulosa cells. This suggests that the up-regulation of LH-LHR signaling is the cause of impaired follicle development. The serum estradiol level was lower, but estradiol production was unchanged in the DKO ovaries. These results suggest that PRIPs are positively involved in the development of follicles via their regulation of LH-LHR signaling and estradiol secretion. Female DKO mice had higher serum levels of insulin, testosterone, and uncarboxylated osteocalcin, which, together with reduced fertility, are reminiscent of polycystic ovary syndrome in humans.
磷脂酶C相关但催化无活性的蛋白PRIP-1和PRIP-2是由独立基因编码的1,4,5-三磷酸肌醇结合蛋白。敲除小鼠体内的这些基因会损害雌性生育能力，表现为怀孕次数减少、幼崽数量减少，以及性腺类固醇和促性腺激素分泌分别减少和增加。我们研究了PRIPs在生育中的作用，重点关注PRIP-1和PRIP-2双敲除（DKO）小鼠的卵巢。在DKO小鼠的卵巢中观察到多个囊性卵泡，超排卵试验显示排卵的卵母细胞数量明显减少。卵丘-卵母细胞复合体显示正常扩张，人工促性腺激素刺激以正常方式调节排卵相关基因，这表明排卵本身可能是正常的。组织学分析显示，DKO小鼠卵巢中闭锁的卵泡较少，特别是在次级卵泡阶段。促黄体生成素受体（LHR）在发育中的卵泡中的表达异常升高，细胞外信号调节蛋白激酶（LH-LHR信号的下游靶点）在DKO颗粒细胞中的磷酸化水平更高。这表明LH-LHR信号的上调是卵泡发育受损的原因。DKO小鼠血清雌二醇水平较低，但卵巢中雌二醇的产生没有变化。这些结果表明，PRIPs通过调节LH-LHR信号和雌二醇分泌，积极参与卵泡的发育。雌性DKO小鼠的血清胰岛素、睾酮和未羧化骨钙素水平较高，再加上生育能力下降，让人联想到人类的多囊卵巢综合征。
