Selvais Charlotte, Gaide Chevronnay Héloïse P, Lemoine Pascale, Dedieu Stéphane, Henriet Patrick, Courtoy Pierre J, Marbaix Etienne, Emonard Hervé
Cell Biology Unit, de Duve Institute, Université catholique de Louvain, B-1200 Brussels, Belgium.
Endocrinology. 2009 Aug;150(8):3792-9. doi: 10.1210/en.2009-0015. Epub 2009 Apr 30.
Cyclic elimination of the endometrium functional layer through menstrual bleeding results from intense tissue breakdown by proteolytic enzymes, mainly members of the matrix metalloproteinase (MMP) family. In contrast to menstrual-restricted MMPs, e.g. interstitial collagenase (MMP-1), gelatinases A (MMP-2) and B (MMP-9) mRNAs are abundant throughout the cycle without detectable tissue degradation at proliferative and secretory phases, implying a tight posttranslational control of both gelatinases. This paper addresses the role of low-density lipoprotein receptor-related protein (LRP)-1 in the endocytic clearance of endometrial gelatinases. LRP-1 mRNA and protein were studied using RT-PCR, Western blotting, and immunolabeling. Posttranslational control of LRP-1 was analyzed in explant culture. The receptor-associated protein (RAP), used as LRP antagonist, strongly increased (pro)gelatinase accumulation in medium conditioned by endometrial explants, suggesting a role for LRP-1 in their clearance. Although LRP-1 mRNA remained constant throughout the cycle, the protein ectodomain vanished at menses. LRP-1 immunolabeling selectively disappeared in areas of extracellular matrix breakdown in menstrual samples. It also disappeared from explants cultured without estrogen and progesterone (EP) due to ectodomain shedding in the medium. The shedding was inhibited by metalloproteinase inhibitors, including a disintegrin and metalloproteinase (ADAM) inhibitor, and by tissue inhibitors of MMPs (TIMP)-3 and -2, but barely by TIMP-1, pointing to ADAM-12 as the putative sheddase. In good agreement, ADAM-12 mRNA expression was repressed by EP. In conclusion, the efficient LRP-1-mediated clearance of gelatinase activity in nonbleeding endometrium is abrogated upon EP withdrawal, due to shedding of LRP-1 ectodomain by a metalloproteinase, presumably ADAM-12, itself regulated by EP.
月经出血导致子宫内膜功能层的周期性脱落，这是由蛋白水解酶，主要是基质金属蛋白酶（MMP）家族成员引起的强烈组织分解所致。与月经期间受限制的MMP不同，例如间质胶原酶（MMP-1），明胶酶A（MMP-2）和B（MMP-9）的mRNA在整个周期中都很丰富，在增殖期和分泌期没有可检测到的组织降解，这意味着这两种明胶酶都受到严格的翻译后调控。本文探讨了低密度脂蛋白受体相关蛋白（LRP）-1在子宫内膜明胶酶内吞清除中的作用。使用逆转录聚合酶链反应（RT-PCR）、蛋白质印迹法和免疫标记法研究了LRP-1的mRNA和蛋白质。在器官培养中分析了LRP-1的翻译后调控。用作LRP拮抗剂的受体相关蛋白（RAP）显著增加了子宫内膜器官培养物条件培养基中（原）明胶酶的积累，表明LRP-1在其清除中起作用。尽管LRP-1的mRNA在整个周期中保持恒定，但该蛋白的胞外域在月经时消失。LRP-1免疫标记在月经样本的细胞外基质分解区域选择性消失。由于培养基中的胞外域脱落，它也从无雌激素和孕激素（EP）培养的器官中消失。这种脱落受到金属蛋白酶抑制剂的抑制，包括去整合素和金属蛋白酶（ADAM）抑制剂，以及MMP组织抑制剂（TIMP）-3和-2，但几乎不受TIMP-1的抑制，这表明ADAM-12是假定的脱落酶。与此一致的是，ADAM-12的mRNA表达受到EP的抑制。总之，由于金属蛋白酶（可能是ADAM-12，其本身受EP调控）导致LRP-1胞外域脱落，在停用EP后，非出血性子宫内膜中LRP-1介导的明胶酶活性的有效清除被消除。
