ORCID
https://orcid.org/0000-0002-2930-1726
Date of Award
8-4-2023
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Sperm from mammalian species are incapable of fertilization at the point of ejaculation. Several maturation steps must take place in the female genital tract that give the sperm the capacity to fertilize, which are collectively called capacitation. The mechanisms behind and interactions between these steps appear to rapidly evolve between species. One of these steps is a hyperpolarization of the membrane to a more negative potential. Human sperm hyperpolarize during capacitation, however the processes that regulate and are regulated by this hyperpolarization remain unclear. This is due in part to discrepancies between what is known about hyperpolarization in other species, such as the mouse where it is well described, and has been observed in humans. Mouse sperm hyperpolarize due to activation of SLO3, potassium channel functionally expressed only in sperm. The first publications describing the potassium currents in human sperm found that the human sperm potassium current, hKSper, is activated by calcium and not pH, which activates mouse sperm potassium currents (IKSper) and SLO3. These characteristics matched the closely related channel SLO1, which is highly conserved and broadly expressed. Shortly after, the human SLO3 channel was cloned and found to share calcium and pH sensitivity with hKSper. Subsequent studies attempted to determine the relative contribution of SLO3 or SLO1 to human sperm hyperpolarization, and by extension fertility, but were hindered by a lack of known loss-of-function mutations or inhibitors selective to the human channels. In 2022, two publications identified three men lacking functional SLO3 who were all infertile. These findings demonstrated that SLO3 is necessary for human male fertility, however they did not preclude the possibility that SLO1 also plays a necessary but not sufficient role in hyperpolarization. In this thesis I describe my work testing putative selective inhibitors for human SLO3. We tested the effect of several inhibitors identified in a high-throughput screen performed by collaborators at Vanderbilt University on human SLO3 and SLO1. Next, we examined the effects of one of these inhibitors, VU0546110, in more depth to demonstrate that selective inhibition of hSLO3 recapitulated the effects of functional hSLO3 loss and completely inhibited hKSper. The screen and effects of VU0546110 were published in the Proceedings of the National Academy of Science and are included in this thesis. Finally, I describe my ongoing work to characterize second-generation inhibitors based off scaffolds identified in the screen with improved selectivity for hSLO3 against other potential off-targets and the methods by which we will test their contraceptive potential. The work presented here provides further evidence of the essential role of hSLO3 in human sperm fertilization and male fertility. Furthermore, this work may serve as the basis for the development of highly selective non-hormonal contraceptives targeting a channel expressed exclusively in sperm.
Language
English (en)
Chair and Committee
Celia Santi
Recommended Citation
Lyon, Maximilian Daniel, "The Sperm-Specific K+ Channel SLO3, a regulator of human fertility and new target for contraception" (2023). Arts & Sciences Electronic Theses and Dissertations. 3119.
https://openscholarship.wustl.edu/art_sci_etds/3119