Analysis of an NHE inhibitor signaling pathway that regulates sperm motility.

描述（由申请人提供）：运动性的获得和维持是精子生理的重要组成部分，在确保生育方面起着关键作用。虽然结构/运动蛋白和离子通道在精子运动中的作用正在深入研究中，并开始变得清晰，但活性膜转运蛋白在调节精子运动中的作用尚未得到很好的理解。然而，最近的证据表明，Na/H交换器（NHE）在维持精子运动的最佳细胞内pH值方面很重要。与这一假设一致的是，敲除精子特异性NHE NHE10会导致小鼠精子不动，这证实了NHE活性与精子活力之间的联系。这些NHE10基因敲除精子的活力可以通过增加细胞内pH值或增加细胞内cAMP浓度来恢复。我们的初步研究表明，为了使cAMP恢复酸化精子的活力，需要一个活跃的NHE。为了确定三种精子NHE亚型中哪一种是cAMP恢复活力所必需的，我们发现了一个令人兴奋的发现，即NHE抑制剂本身可以完全恢复NHE10敲除精子的活力。在这里提出的研究中，我们将定义参与由NHE抑制剂激活的Camp依赖性运动恢复途径的细胞内信号分子，我们将确定精子中发现的三种NHE中哪一种启动了这一途径，以及这些同工异构体中哪一种作为最终的下游效应物来恢复运动。这些研究不仅对确定NHE在调节精子运动中所起的作用很重要，而且还可能具有医学意义：人类精子也含有这种NHE抑制剂启动的运动调节信号通路，因此一部分不育男性可能由于该通路的破坏而不育，该通路的特定抑制剂或激活剂可能被开发为男性生育/不育治疗的疗法。

DESCRIPTION (provided by applicant): Acquisition and maintenance of motility are important components of sperm physiology in that they play critical roles in ensuring fertility. While the roles that structural/motor proteins and ion channels play in sperm motility is under intense investigation and is beginning to become clear, the roles that active membrane transporters play in regulating sperm motility is not as well understood. However, recent evidence suggests that the Na/H exchanger (NHE) is important in maintaining an optimal intracellular pH critical for sperm motility. In agreement with this hypothesis, knockout of the sperm-specific NHE, NHE10, results in immotile mouse sperm confirming a link between NHE activity and sperm motility. The motility of these NHE10 knockout sperm can be restored either by increasing intracellular pH or by increasing intracellular cAMP concentration. Our preliminary studies demonstrate that in order for cAMP to restore motility to acidified sperm, an active NHE is required. Towards defining which of the three sperm NHE isoforms is required for cAMP to restore motility, we made the exciting discovery that an inhibitor of the NHE, by itself, can completely restore motility to NHE10 knockout sperm. In the studies proposed here, we will define the intracellular signaling molecules participating in the Camp dependent, motility-restoring pathway activated by the NHE inhibitor, we will identify which of the three NHE found in sperm initiate this pathway, and which of these isoforms serves as the ultimate downstream effectors to restore motility. These studies will not only be important for defining the role that the NHEs play in regulating sperm motility but they also may have medically relevant implications: Human sperm also contains this NHE inhibitor initiated motility-regulating signaling pathway and therefore a subset of infertile men may be infertile due to disruption in this pathway and specific inhibitors or activators of this pathway could be developed as therapies for male fertility/infertility treatments. PUBLIC HEALTH RELEVANCE: It is well accepted that adequate sperm motility is one of the key components of male fertility. Individuals with poorly motile or immotile sperm are typically infertile. In the US alone an estimated 10-15% of couples are considered infertile as defined by World Health Organization criteria. Among them, it is estimated that 30% of these couples are infertile due to the male partner. Therefore, a thorough understanding of the molecular events that allows sperm to acquire and maintain motility will help us to address issues related to infertility associated with poorly motile or immotile sperm. In addition, the knowledge gained in understanding the molecules involved in maintaining sperm motility could be useful in developing targets for effective male contraception.