EXPRESSION OF HEAT SHOCK GENES IN MOUSE SPERMATOGENIC CELLS

工作概要：本项目的目的是确定 两种独特的热休克蛋白70在男性生殖细胞发育和 功能 热休克蛋白70蛋白是分子伴侣， 新生多肽的折叠和变性蛋白质的重折叠 在热休克和其他压力下。 HSP 70 -1和HSP 70 - 3蛋白是 在大多数细胞中对应激反应高度诱导，但在 HSP 70 -2和HSC 70 T蛋白仅在生精细胞中表达， 以及对发育线索的反应。 因为HSP 70 -2是 在减数分裂过程中大量合成，与其他hsp 70相似 我们假设HSP 70 -2是一种已知的伴侣蛋白， 蛋白质在这一阶段的关键事件中的作用 精子发生 当敲除Hsp 70 -2基因时， 导致所有粗线期的发育停滞和凋亡 精母细胞减数分裂I期G2/M期转换。 由于这 事件需要细胞周期蛋白B1依赖的Cdc 2激酶活性，结果 表明HSP 70 -2是Cdc 2激活所需的分子伴侣。 虽然Cdc 2存在于Hsp 70 -2基因敲除小鼠的睾丸中，但它确实存在于Hsp 70 -2基因敲除小鼠的睾丸中。 不与细胞周期蛋白B1形成异二聚体，缺乏激酶活性。 将重组HSP 70 -2蛋白加入到小鼠睾丸匀浆中， Hsp 70 -2基因敲除小鼠恢复Cdc 2形成异源二聚体的能力 HSP 70 - 2与细胞周期蛋白B1结合，成为一种活性激酶，证实HSP 70 -2是 Cdc 2的伴侣 HSC 70 T蛋白仅存在于精子细胞中， 在雄性生殖细胞发育的后减数分裂阶段。 通过类比 与HSC 70 -2，我们假设HSC 70 T是一个伴侣，独特的， 参与减数分裂后生殖细胞发育的蛋白质。 然而，男性 hsc 70 t基因敲除小鼠具有生育能力，精子发育没有改变。 这表明精子细胞中存在的其他hsp 70蛋白可以 弥补精子发育过程中HSC 70 T蛋白的缺失 在正常情况下。 尚待确定是否缺乏HSC 70 T 增加精子细胞或精子对 热休克或环境化学品。

Summary of Work: The aim of this project is to determine the roles of two unique hsp70 heat-shock proteins in male germ cell development and function. The hsp70 proteins are molecular chaperones that assist in the folding of nascent polypeptides and in refolding of denatured proteins following heat shock and other stresses. HSP70-1 and -3 proteins are highly induced in most cells in response to stress but poorly induced in spermatogenic cells, while HSP70-2 and HSC70T proteins are expressed only in these cells and in response to developmental cues. Because HSP70-2 is synthesized in abundance during meiosis and is similar to other hsp70 proteins known to be chaperones, we hypothesized that HSP70-2 serves such a role for proteins involved in critical events during this phase of spermatogenesis. This was confirmed when a knock-out of the Hsp70-2 gene resulted in developmental arrest and apoptosis of all pachytene spermatocytes at the G2/M-phase transition of meiosis I. SInce this event requires cyclin B1-dependent Cdc2 kinase activity, the results suggested that HSP70-2 is a chaperone required for Cdc2 activation. Although Cdc2 was present in the testis of Hsp70-2 knock-out mice, it did not form a heterodimer with cyclin B1 and lacked kinase activity. Addition of recombinant HSP70-2 protein to a homogenate of testis from Hsp70-2 knock-out mice restored the ability of Cdc2 to form a heterodimer with cyclin B1 and to become an active kinase, confirming that HSP70-2 is a chaperone for Cdc2. The HSC70T protein is present only in spermatids, during the post-meiotic phase of male germ cell development. By analogy with HSC70-2, we hypothesized that HSC70T is a chaperone for unique proteins involved in post-meiotic germ cell development. However, male Hsc70t knock-out mice are fertile and sperm development is not altered. This suggests that other hsp70 proteins present in spermatids can compensate for the absence of HSC70T protein during sperm development under normal conditions. It remains to be determined if lack of HSC70T increases the sensitivity of spermatids or sperm to the effects of heat-shock or environmental chemicals.