SLO3: A Conserved Regulator of Sperm Membrane Potential

Lyon, Maximilian D.; Ferreira, Juan J.; Li, Ping; Bhagwat, Shweta; Butler, Alice; Anderson, Kelsey; Polo, Mónica Patricia; Santi, Celia M.

doi:10.3390/ijms241311205

Cited by 2 publications

(2 citation statements)

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“…An important regulator of SLO3 is the leucine-rich-repeat-containing protein 52 (LRRC52) 40 . The significance of LRRC52 for SLO3 activity was demonstrated in Lrrc52 KO mice, where alkalinization failed to hyperpolarize sperm Em to the same extent as in WT sperm, suggesting a crucial role for LRCC52 in SLO3 response to alkalinization 39 . In this regard, Na + /H + exchangers (NHEs) have emerged as potential contributors to sperm alkalinization during capacitation.…”

Section: Discussionmentioning

confidence: 94%

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The sodium-proton exchangers sNHE and NHE1 control plasma membrane hyperpolarization in mouse sperm

Novero,

Rodríguez,

De la Vega Beltrán

et al. 2024

Preprint

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Sperm capacitation, crucial for fertilization, occurs in the female reproductive tract and can be replicatedin vitrousing a medium rich in bicarbonate, calcium, and albumin. These components trigger the cAMP-PKA signaling cascade, proposed to promote hyperpolarization of the mouse sperm plasma membrane through activation of SLO3 K+channel. Hyperpolarization is a hallmark of capacitation: proper membrane hyperpolarization renders higherin vitrofertilizing ability, whileSlo3KO mice are infertile. However, the precise regulation of SLO3 opening remains elusive. Our study challenges the involvement of PKA in this event and reveals the role of Na+/H+exchangers. During capacitation, calcium increase through CatSper channels activates NHE1, while cAMP directly stimulates the sperm-specific NHE, collectively promoting the alkalinization threshold needed for SLO3 opening. Hyperpolarization then feeds back Na+/H+activity. Our work is supported by pharmacology, and a plethora of KO mouse models, and proposes a novel pathway leading to hyperpolarization.TeaserAlkalinization of sperm cytoplasm activates potassium channels to hyperpolarize the plasma membrane in a PKA independent cascade.

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Section: Discussionmentioning

confidence: 94%

“…The mouse SLO3 channel was found to be activated by intracellular alkalinization 38 , though the precise mechanism of its modulation by pHi remains unresolved (for an in-depth review, see 39 ). An important regulator of SLO3 is the leucine-rich-repeat-containing protein 52 (LRRC52) 40 .…”

Section: Discussionmentioning

confidence: 99%

The sodium-proton exchangers sNHE and NHE1 control plasma membrane hyperpolarization in mouse sperm

Novero,

Rodríguez,

De la Vega Beltrán

et al. 2024

Preprint

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Flagellar pH homeostasis mediated by Na+/H+ exchangers regulates human sperm functions through coupling with CatSper and KSper activation

Liang,

Ji,

Song

et al. 2024

Human Reproduction

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STUDY QUESTION Whether and how do Na+/H+ exchangers (NHEs) regulate the physiological functions of human sperm? SUMMARY ANSWER NHE-mediated flagellar intracellular pH (pHi) homeostasis facilitates the activation of the pH-sensitive, sperm-specific Ca2+ channel (CatSper) and the sperm-specific K+ channel (KSper), which subsequently modulate sperm motility, hyperactivation, flagellar tyrosine phosphorylation, and the progesterone (P4)-induced acrosome reaction. WHAT IS KNOWN ALREADY Sperm pHi alkalization is an essential prerequisite for the acquisition of sperm-fertilizing capacity. Different sperm functions are strictly controlled by particular pHi regulatory mechanisms. NHEs are suggested to modulate sperm H+ efflux. STUDY DESIGN, SIZE, DURATION This was a laboratory study that used samples from >50 sperm donors over a period of 1 year. To evaluate NHE action on human sperm function, 5-(N,N-dimethyl)-amiloride (DMA), a highly selective inhibitor of NHEs, was utilized. All experiments were repeated at least five times using different individual sperm samples or cells. PARTICIPANTS/MATERIALS, SETTING, METHODS By utilizing the pH fluorescent indicator pHrodo Red-AM, we detected alterations in single-cell pHi value in human sperm. The currents of CatSper and KSper in human sperm were recorded by the whole-cell patch-clamp technique. Changes in population and single-cell Ca2+ concentrations ([Ca2+]i) of human sperm loaded with Fluo 4-AM were measured. Membrane potential (Vm) and population pHi were quantitatively examined by a multimode plate reader after sperm were loaded with 3,3′-dipropylthiadicarbocyanine iodide and 2′,7′-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein, acetoxymethyl ester, respectively. Sperm motility parameters were assessed by a computer-assisted semen analysis system. Tyrosine phosphorylation was determined by immunofluorescence, and sperm acrosome reaction was evaluated by Pisum sativum agglutinin-FITC staining. MAIN RESULTS AND THE ROLE OF CHANCE DMA-induced NHEs inhibition severely acidified the human sperm flagellar pHi from 7.20 ± 0.04 to 6.38 ± 0.12 (mean ± SEM), while the effect of DMA on acrosomal pHi was less obvious (from 5.90 ± 0.13 to 5.57 ± 0.12, mean ± SEM). The whole-cell patch-clamp recordings revealed that NHE inhibition remarkably suppressed alkalization-induced activation of CatSper and KSper. As a consequence, impairment of [Ca2+]i homeostasis and Vm maintenance were detected in the presence of DMA. During the capacitation process, pre-treatment with DMA for 2 h potently decreased sperm pHi, which in turn decreased sperm motility and kinetic parameters. Sperm capacitation-associated functions, including hyperactivation, tyrosine phosphorylation, and P4-induced acrosome reaction, were also compromised by NHE inhibition. LARGE SCALE DATA N/A. LIMITATIONS, REASONS FOR CAUTION This was an in vitro study. Caution should be taken when extrapolating these results to in vivo applications. WIDER IMPLICATIONS OF THE FINDINGS This study revealed that NHEs are important physiological regulators for human CatSper and KSper, which are indispensable for human sperm fertility, suggesting that malfunction of NHEs could be an underlying mechanism for the pathogenesis of male infertility. FUNDING/COMPETING INTEREST(S) This work was supported by the National Natural Science Foundation of China (32271167 and 81871202 to X.Z.), Jiangsu Innovation and Entrepreneurship Talent Plan (JSSCRC20211543 to X.Z.), the Social Development Project of Jiangsu Province (No. BE2022765 to X.Z.), the Society and livelihood Project of Nantong City (No. MS22022087 to X.Z.), and the Natural Science Foundation of Jiangsu Province (BK20220608 to H.K.). The authors have no competing interests to declare.

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SLO3: A Conserved Regulator of Sperm Membrane Potential

Cited by 2 publications

References 113 publications

The sodium-proton exchangers sNHE and NHE1 control plasma membrane hyperpolarization in mouse sperm

The sodium-proton exchangers sNHE and NHE1 control plasma membrane hyperpolarization in mouse sperm

Flagellar pH homeostasis mediated by Na+/H+ exchangers regulates human sperm functions through coupling with CatSper and KSper activation

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