EXPRESSION OF HEAT SHOCK GENES IN MOUSE SPERMATOGENIC CELLS

工作总结：本项目的目标是 确定两种独特的HSP70热休克蛋白在 男性生殖细胞的发育和功能。HSP70蛋白是 帮助新生细胞折叠的分子伴侣 多肽和变性蛋白质加热后的复性 震惊和其他压力。HSP70-1和-3蛋白高度 在大多数细胞中诱导对应激反应，但在 生精细胞，而HSP70-2和HSC70T蛋白 仅在这些细胞中表达，并对发育线索做出反应。 因为HSP70-2在减数分裂过程中大量合成， 与其他已知的伴侣蛋白HSP70类似，我们 假设HSP70-2对所涉及的蛋白质起到这样的作用 在精子发生的这一阶段的关键事件中。这是 当Hsp70-2基因敲除导致 所有粗线期精母细胞的发育停滞和凋亡 在减数分裂的G2/M期。由于这一事件需要 细胞周期蛋白B1依赖的CDC2激酶活性，结果提示 HSP70-2是CDC2激活所需的伴侣蛋白。虽然 在Hsp70-2基因敲除小鼠的睾丸中发现了Cdc2。 不与细胞周期蛋白B1形成异二聚体，缺乏激酶活性。 重组HSP70-2蛋白在猪血清匀浆中的添加 Hsp70-2基因敲除小鼠的睾丸恢复了CDC2的能力 与细胞周期蛋白B1形成异二聚体，成为活性激酶， 证实HSP70-2是CDc2的伴侣。HSC70T 蛋白质只存在于减数分裂后的精子细胞中。 雄性生殖细胞的发育。通过类比HSC70-2，我们 假设HSC70T是独特蛋白质的伴侣 参与减数分裂后生殖细胞的发育。然而，男性 Hsc70T基因敲除的小鼠可以生育，但精子发育不佳 被更改了。这表明其他HSP70蛋白存在于 精子细胞可以弥补HSC70T蛋白的缺失 在正常情况下精子发育过程中。它还有待于 确定缺乏HSC70T是否会增加对 精子细胞或精子对热休克或环境的影响 化学制品。

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.