Structure and Function of Ion Channels Regulating Sperm Motility-An Overview.

Karolina Nowicka-Bauer,Monika Szymczak-Cendlak

doi:10.3390/ijms22063259

Karolina Nowicka-Bauer, Monika Szymczak-Cendlak

Open Access

https://doi.org/10.3390/ijms22063259

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Abstract

Sperm motility is linked to the activation of signaling pathways that trigger movement. These pathways are mainly dependent on Ca2+, which acts as a secondary messenger. The maintenance of adequate Ca2+ concentrations is possible thanks to proper concentrations of other ions, such as K+ and Na+, among others, that modulate plasma membrane potential and the intracellular pH. Like in every cell, ion homeostasis in spermatozoa is ensured by a vast spectrum of ion channels supported by the work of ion pumps and transporters. To achieve success in fertilization, sperm ion channels have to be sensitive to various external and internal factors. This sensitivity is provided by specific channel structures. In addition, novel sperm-specific channels or isoforms have been found with compositions that increase the chance of fertilization. Notably, the most significant sperm ion channel is the cation channel of sperm (CatSper), which is a sperm-specific Ca2+ channel required for the hyperactivation of sperm motility. The role of other ion channels in the spermatozoa, such as voltage-gated Ca2+ channels (VGCCs), Ca2+-activated Cl-channels (CaCCs), SLO K+ channels or voltage-gated H+ channels (VGHCs), is to ensure the activation and modulation of CatSper. As the activation of sperm motility differs among metazoa, different ion channels may participate; however, knowledge regarding these channels is still scarce. In the present review, the roles and structures of the most important known ion channels are described in regard to regulation of sperm motility in animals.

Highlights

Sperm motility is a unique characteristic of sperm physiology that is necessary to achieve egg fertilization
The review describes some of the more important ion channels involved in the regulation of sperm motility in different animal species based on the available literature
A clear consensus has emerged from the reviewed literature, where the known ion channels governing sperm motility are mainly voltage-gated channels

Summary

Introduction

Sperm motility is a unique characteristic of sperm physiology that is necessary to achieve egg fertilization. The induction of motility in the epididymis is linked to the gradual transition from phosphatase to kinase activities, and with the gradual phosphorylation of proteins [8] This basic type of motility is characterized by low-amplitude symmetrical tail movements that enable linear motility for spermatozoa; to ensure the success of fertilization, spermatozoa must become hyperactivated after entering the uterus (reviewed in Reference [8]). Despite the varying locations and methods of fertilization, the activation and maintenance of sperm motility in all animals is dependent on the membrane potential (Vm), intracellular pH (pHi ), and proper balance of intracellular ions All of these factors are tightly interlinked, and their effective cooperation provides cellular signals required for sufficient sperm motility. The structure and physiological role of some of the important ion channels that are critical to spermatozoa motility are discussed

Calcium Channels

Chloride Channels

Potassium Channels

Conclusions