Chemosensory signal transduction in human sperm

在输卵管卵丘细胞周围的卵母细胞释放孕酮。在人类精子中，孕酮通过一种非基因组机制激活精子特异的钙通道CatSper。随之而来的钙离子增加控制着精子的趋化性、过度激活和顶体胞吐，从而协调受精过程。黄体酮诱导的钙信号由快速的钙瞬变和随后缓慢而持续的钙升高组成。钙信号的瞬时和持续阶段都依赖于通过CatSper的钙离子内流。然而，影响钙反应的机制尚不清楚。特别是，通过CatSper抑制钙离子内流的机制仍然不清楚。我们认为这可能涉及到CatSper与精子特异性钙激活的K+通道slo3之间的相互作用：通过CatSper的钙离子内流可能激活slo3，随后的钙诱导的超极化降低了CatSper的开放概率，从而减少了钙离子内流。在这项研究工作中，我们想仔细研究这一模式。为此，我们想用快速电压敏感染料和动态停流荧光法，通过光学方法研究孕酮对人精子S膜电压(Vm)的影响。为了研究CatSper和Slo3的相互作用，阐明Ca~(2+)和Vm信号是否以及如何相互联系，并描绘事件的顺序，我们将通过荧光多路复用同时监测孕酮诱导的Ca~(2+)和Vm反应。用这项技术获得的初步数据有力地支持了这样的观点，即Vm和Ca~(2+)信号在人类精子中紧密地缠绕在一起，并且Slo3是非基因组孕酮信号通路的关键决定因素。

In the oviduct cumulus cells surrounding the oocyte release progesterone. In human sperm, progesterone activates the sperm-specific Ca2+ channel CatSper by a non-genomic mechanism. The ensuing Ca2+ increase controls chemotaxis, hyperactivation, and acrosomal exocytosis of sperm and, thereby, orchestrates the fertilization process. The progesterone-induced Ca2+ signal consists of a rapid Ca2+ transient followed by a slower, sustained Ca2+ elevation. Both the transient and sustained phase of the Ca2+ signal rest on Ca2+ influx via CatSper. The mechanisms shaping the Ca2+ response are, however, unknown. In particular, the mechanism that curtails Ca2+ influx via CatSper has remained elusive. We proposed that this might involve an interplay between CatSper and the sperm-specific Ca2+-activated K+ channel Slo3: Ca2+ influx via CatSper might activate Slo3 and the ensuing Ca2+-induced hyperpolarization decreases the open probability of CatSper, curtailing the Ca2+ influx. In this research endeavor, we want to scrutinize this model. To this end, we want to investigate by optical methods progesterone-induced changes of human sperm´s membrane voltage (Vm) using fast voltage-sensitive dyes and kinetic stopped-flow fluorimetry. To study the interplay of CatSper and Slo3, to elucidate whether and how Ca2+ and Vm signaling is interconnected, and to delineate the sequence of events, we will simultaneously monitor progesterone-evoked Ca2+ and Vm responses by fluorescence multiplexing. Preliminary data obtained with this technique strongly support the notion that Vm and Ca2+ signaling are intimately entangled in human sperm and that Slo3 is a critical determinant of the non-genomic progesterone-signaling pathway.