O'Sullivan Colleen M, Liu Shi Ying, Karpinka J Bradley, Rancourt Derrick E
Department of Biochemistry and Molecular Biology, Southern Alberta Cancer Research Centre, University of Calgary, Alberta, Canada.
Mol Reprod Dev. 2002 Jul;62(3):328-34. doi: 10.1002/mrd.10142.
Embryo hatching and outgrowth are the first critical steps on the way to a successful pregnancy. It is generally held that serine proteases are responsible for this process, although the exact mechanisms of action are not clearly understood. Recently, we described two novel implantation serine proteinase (ISP) genes that are expressed during the implantation period. The ISP1 gene encodes the embryo-derived enzyme strypsin, which is necessary for blastocyst hatching in vitro and the initiation of invasion. The ISP2 gene, which encodes a related tryptase, is expressed in endometrial glands and is regulated by progesterone during the peri-implantation period. Based on similarities between ISP2 gene expression and that of a progesterone-regulated lumenal serine proteinase activity associated with lysis of the zona pellucida, we have suggested that the strypsin related protein, ISP2, may encode a zona lysin proteinase. As tryptases naturally assemble to form tetrameric structures, we have hypothesized that ISP1 and ISP2 tetramerize to form strypsin and lysin, respectively. In this study, we demonstrate that like ISP2, the ISP1 gene is also expressed in endometrial glands and is positively regulated by progesterone during implantation. Using in situ hybridization of adjacent tissue sections, we show that the ISP1 and ISP2 genes are co-expressed within the endometrial gland. Following evidence that ISP1 and 2 can efficiently form homotetramers and heterotetramers in silico, we suggest that ISP heterotetramers may be also be secreted into the uterine lumen during the implantation period. That the embryonic hatching enzyme, may also be secreted into the uterine lumen from uterus, may provide insight into the mechanisms of hatching and implantation initiation.
胚胎孵化和生长是成功妊娠过程中的首个关键步骤。一般认为丝氨酸蛋白酶负责这一过程，尽管其确切作用机制尚不清楚。最近，我们描述了两个在着床期表达的新型着床丝氨酸蛋白酶（ISP）基因。ISP1基因编码胚胎来源的酶——胰蛋白酶，它是体外囊胚孵化和侵袭起始所必需的。ISP2基因编码一种相关的类胰蛋白酶，在子宫内膜腺体中表达，并在着床期受孕酮调节。基于ISP2基因表达与一种与透明带溶解相关的孕酮调节的腔隙丝氨酸蛋白酶活性的相似性，我们推测与胰蛋白酶相关的蛋白质ISP2可能编码一种透明带溶解蛋白酶。由于类胰蛋白酶自然组装形成四聚体结构，我们推测ISP1和ISP2分别四聚化形成胰蛋白酶和溶解素。在本研究中，我们证明与ISP2一样，ISP1基因也在子宫内膜腺体中表达，且在着床期受孕酮正向调节。通过对相邻组织切片进行原位杂交，我们发现ISP1和ISP2基因在子宫内膜腺体内共表达。基于ISP1和2在计算机模拟中能有效形成同型四聚体和异型四聚体的证据，我们认为ISP异型四聚体在着床期也可能分泌到子宫腔中。胚胎孵化酶也可能从子宫分泌到子宫腔中，这可能为孵化和着床起始机制提供线索。
