Reproductive Medicine Center, The Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, 210008, People's Republic of China.
Cell Death Dis. 2018 Feb 19;9(3):291. doi: 10.1038/s41419-018-0317-3.
Endometriosis (ENDO) is a common gynecological disease that causes infertility in many women. Previous studies noted that the dysregulation of Homeo box A10 (HOXA10) in the endometrium of women with ENDO was involved in the failure of embryo implantation. However, the mechanism by which HOXA10 expression is reduced in women with ENDO is still poorly understood. Here we found that a member of the calcium (Ca)-dependent cysteine protease family calpain7 (CAPN7), negatively correlated with HOXA10, was highly expressed in the endometrium of infertile women with ENDO and was significantly downregulated during the window of embryo implantation in mice. Overexpression of CAPN7 in Ishikawa cells or in the uterus of mice inhibited embryo implantation in vitro and in vivo. In the current study, we identified a sequence rich in proline, glutamic acid, serine, and threonine (PEST sequence) that enhanced the Ca-dependent degradation of HOXA10 by CAPN7. Furthermore, the interaction between HOXA10 and CAPN7 repressed the transcriptional activity and protein stability of HOXA10. In contrast, the administration of the calpain inhibitor ALLN reversed the CAPN7-induced HOXA10 degradation. Moreover, truncation of the PEST motif in HOXA10 abolished its CAPN7-dependent proteolysis. These studies reveal a novel pattern of HOXA10 regulation via PEST sequence-mediated calpain proteolysis that was demonstrated to be reversed by a calpain inhibitor. Thus, the inhibition of CAPN7-induced HOXA10 degradation may represent a novel potential therapeutic method to improve impaired embryo implantation in women with ENDO.
子宫内膜异位症（ENDO）是一种常见的妇科疾病，可导致许多女性不孕。先前的研究表明，ENDO 患者子宫内膜中同源盒 A10（HOXA10）的失调参与了胚胎着床失败。然而，ENDO 患者中 HOXA10 表达减少的机制仍知之甚少。在这里，我们发现钙（Ca）依赖性半胱氨酸蛋白酶家族成员钙蛋白酶 7（CAPN7）与 HOXA10 呈负相关，在患有 ENDO 的不孕妇女的子宫内膜中高度表达，并在小鼠胚胎着床窗口期间明显下调。CAPN7 在 Ishikawa 细胞或小鼠子宫中的过表达抑制了体外和体内胚胎着床。在本研究中，我们鉴定了一个富含脯氨酸、谷氨酸、丝氨酸和苏氨酸（PEST 序列）的序列，该序列增强了 CAPN7 对 HOXA10 的 Ca 依赖性降解。此外，HOXA10 和 CAPN7 之间的相互作用抑制了 HOXA10 的转录活性和蛋白稳定性。相反，钙蛋白酶抑制剂 ALLN 逆转了 CAPN7 诱导的 HOXA10 降解。此外，HOXA10 中 PEST 基序的截断消除了其对 CAPN7 依赖性蛋白水解的作用。这些研究揭示了一种通过 PEST 序列介导的钙蛋白酶蛋白水解来调节 HOXA10 的新模式，该模式被钙蛋白酶抑制剂逆转。因此，抑制 CAPN7 诱导的 HOXA10 降解可能代表改善 ENDO 患者受损胚胎着床的一种新的潜在治疗方法。
