All four CatSper ion channel proteins are required for male fertility and sperm cell hyperactivated motility

Abstract

Mammalian spermatozoa become motile at ejaculation, but before they can fertilize the egg, they must acquire more thrust to penetrate the cumulus and zona pellucida. The forceful asymmetric motion of hyperactivated spermatozoa requires Ca 2؉ entry into the sperm tail by an alkalinization-activated voltage-sensitive Ca 2؉ -selective current (ICatSper). Hyperactivation requires CatSper1 and CatSper2 putative ion channel genes, but the function of two other related genes (CatSper3 and CatSper4) is not known. Here we show that targeted disruption of murine CatSper3 or CatSper4 also abrogated I CatSper , sperm cell hyperactivated motility and male fertility but did not affect spermatogenesis or initial motility. Direct protein interactions among CatSpers, the sperm specificity of these proteins, and loss of I CatSper in each of the four CatSper ؊/؊ mice indicate that CatSpers are highly specialized flagellar proteins.calcium ͉ contraception ͉ flagella S permatozoa first acquire the potential for motility in the epididymis. They are capacitated in the female reproductive tract (1), where they acquire hyperactivated motility and other attributes that enable fertilization (2). During hyperactivation, the sperm tail motion changes from symmetric, fast, and low amplitude (sinusoidal) to asymmetric, slow, and large amplitude (whip-like; refs. 3-5). Hyperactivation is required for fertilization, providing the force needed to free the sperm cell from the oviductal reservoir and to penetrate the cumulus and zona pellucida surrounding the egg (1, 6, 7).Sperm cells become motile and progress directionally once they enter the female reproductive tract. Ca 2ϩ -independent flagellar dynein and ATP orchestrate the low-amplitude sinusoidal-activated motility of the tail. As the sperm cells encounter a more alkaline environment in the higher female reproductive tract, they hyperactivate, a process that requires Ca 2ϩ entry (3,8,9). Studies with antibodies or nucleotide probes have labeled several Ca 2ϩ -permeant channels, including voltage-sensitive Ca 2ϩ -selective channels (CatSpers and CaVs), cyclic nucleotide-gated channels, and transient receptor potential channels, in spermatocytes or spermatozoa (10-18). However, recent patch-clamp recordings of mouse epididymal spermatozoa (19) show that the predominant Ca 2ϩ -carrying current requires the CatSper1 gene that encodes a six-transmembrane-spanning protein of the voltage-gated ligand ion channel superfamily (20). In both whole-cell and perforatedpatch configurations, the Ca 2ϩ -selective current (I CatSper ) originated from the principal piece of the sperm tail and was absent in spermatozoa from CatSper1 Ϫ/Ϫ mice. CatSper1 Ϫ/Ϫ and CatSper2 Ϫ/Ϫ male mice are infertile (11,21), and sperm cells from CatSper1 Ϫ/Ϫ and CatSper2 Ϫ/Ϫ mice are unable to hyperactivate (4, 21). I CatSper was dramatically potentiated by a rise in intracellular pH, suggesting that the alkalinization that occurs during sperm capacitation activates I CatSper to increase intracellular [Ca 2ϩ ] and induce hypera...

Flagellar ion channels of sperm: similarities and differences between species

“…This weak voltage dependency is thought to be the result of heterogeneity of the arginine and lysine composition of the putative voltage sensor domains within the CatSper ␣ subunits. The characteristic CatSper current (I CatSper ) is lost in mice lacking any of the CatSper ␣ subunits (CatSper1-4) or the accessory subunit CatSper ␦ and, as previously mentioned, are all infertile due to an inability of CatSper null spermatozoa to hyperactivate resulting in an inability of sperm to pass into the oviduct to reach the egg [9,10,16,21,22,24,[71][72][73][81][82][83].…”

“…2). Loss of any one member of the complex is detrimental to male fertility due to their interdependent protein expression in spermatozoa though CatSper␤ and CatSper␥ null mice have yet to be observed [9,19,22,24,49,74]. Humans with mutations within the CatSper1 or CatSper2 genes were also shown to be infertile revealing CatSper's importance as a general mechanism in mammalian fertility potential [6,[75][76][77][78][79][80].…”

Progesterone significantly enhances the mobility of boar spermatozoa

“…Calcium influx through the CatSper ion channel is likely to contribute to all of these processes [35][36][37][38][39][40] and recently progesterone has been demonstrated to directly activate this channel in human, but not mouse sperm [11,12]. The characterisation of the effects of progesterone on boar sperm has been limited.…”

Le chimiotactisme du spermatozoïde est régulé par la fixation de la progestérone sur le canal calcique CATSPER

“…Le canal CATSPER est un canal calcique essentiel à la mobilité du spermatozoïde [3]. Sa structure est similaire à celle des canaux potassiques et forme un pore constitué de quatre sous-unités différentes (CATSPER 1-4), chacune comportant six segments transmembranaires [4]. Au moins deux sous-unités accessoires (CATSPER  et ) sont liées à ce canal et sont néces-saires à son fonctionnement [5,6].…”

“…Finalement, ils ont aussi montré une différence de réponse entre les spermatozoïdes selon qu'ils ont ou non subi l'étape de capacitation 1 [3]. miR-122 apparaît donc comme un élément crucial du réseau de régulation de l'expression des gènes hépatiques et pourrait être nécessaire à la synchronisation des gènes à l'interface entre plusieurs voies métaboliques (revue [4]). …”