Cargando…

Conserved Mechanism of Bicarbonate-Induced Sensitization of CatSper Channels in Human and Mouse Sperm

To fertilize an egg, mammalian sperm must undergo capacitation in the female genital tract. A key contributor to capacitation is the calcium (Ca(2+)) channel CatSper, which is activated by membrane depolarization and intracellular alkalinization. In mouse epididymal sperm, membrane depolarization by...

Descripción completa

Detalles Bibliográficos
Autores principales: Ferreira, Juan J., Lybaert, Pascale, Puga-Molina, Lis C., Santi, Celia M.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Frontiers Media S.A. 2021
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8505895/
https://www.ncbi.nlm.nih.gov/pubmed/34650979
http://dx.doi.org/10.3389/fcell.2021.733653
_version_ 1784581632519307264
author Ferreira, Juan J.
Lybaert, Pascale
Puga-Molina, Lis C.
Santi, Celia M.
author_facet Ferreira, Juan J.
Lybaert, Pascale
Puga-Molina, Lis C.
Santi, Celia M.
author_sort Ferreira, Juan J.
collection PubMed
description To fertilize an egg, mammalian sperm must undergo capacitation in the female genital tract. A key contributor to capacitation is the calcium (Ca(2+)) channel CatSper, which is activated by membrane depolarization and intracellular alkalinization. In mouse epididymal sperm, membrane depolarization by exposure to high KCl triggers Ca(2+) entry through CatSper only in alkaline conditions (pH 8.6) or after in vitro incubation with bicarbonate (HCO(3)(–)) and bovine serum albumin (capacitating conditions). However, in ejaculated human sperm, membrane depolarization triggers Ca(2+) entry through CatSper in non-capacitating conditions and at lower pH (< pH 7.4) than is required in mouse sperm. Here, we aimed to determine the mechanism(s) by which CatSper is activated in mouse and human sperm. We exposed ejaculated mouse and human sperm to high KCl to depolarize the membrane and found that intracellular Ca(2+) concentration increased at pH 7.4 in sperm from both species. Conversely, intracellular Ca(2+) concentration did not increase under these conditions in mouse epididymal or human epididymal sperm. Furthermore, pre-incubation with HCO(3)(–) triggered an intracellular Ca(2+) concentration increase in response to KCl in human epididymal sperm. Treatment with protein kinase A (PKA) inhibitors during exposure to HCO(3)(–) inhibited Ca(2+) concentration increases in mouse epididymal sperm and in both mouse and human ejaculated sperm. Finally, we show that soluble adenylyl cyclase and increased intracellular pH are required for the intracellular Ca(2+) concentration increase in both human and mouse sperm. In summary, our results suggest that a conserved mechanism of activation of CatSper channels is present in both human and mouse sperm. In this mechanism, HCO(3)(–) in semen activates the soluble adenylyl cyclase/protein kinase A pathway, which leads to increased intracellular pH and sensitizes CatSper channels to respond to membrane depolarization to allow Ca(2+) influx. This indirect mechanism of CatSper sensitization might be an early event capacitation that occurs as soon as the sperm contact the semen.
format Online
Article
Text
id pubmed-8505895
institution National Center for Biotechnology Information
language English
publishDate 2021
publisher Frontiers Media S.A.
record_format MEDLINE/PubMed
spelling pubmed-85058952021-10-13 Conserved Mechanism of Bicarbonate-Induced Sensitization of CatSper Channels in Human and Mouse Sperm Ferreira, Juan J. Lybaert, Pascale Puga-Molina, Lis C. Santi, Celia M. Front Cell Dev Biol Cell and Developmental Biology To fertilize an egg, mammalian sperm must undergo capacitation in the female genital tract. A key contributor to capacitation is the calcium (Ca(2+)) channel CatSper, which is activated by membrane depolarization and intracellular alkalinization. In mouse epididymal sperm, membrane depolarization by exposure to high KCl triggers Ca(2+) entry through CatSper only in alkaline conditions (pH 8.6) or after in vitro incubation with bicarbonate (HCO(3)(–)) and bovine serum albumin (capacitating conditions). However, in ejaculated human sperm, membrane depolarization triggers Ca(2+) entry through CatSper in non-capacitating conditions and at lower pH (< pH 7.4) than is required in mouse sperm. Here, we aimed to determine the mechanism(s) by which CatSper is activated in mouse and human sperm. We exposed ejaculated mouse and human sperm to high KCl to depolarize the membrane and found that intracellular Ca(2+) concentration increased at pH 7.4 in sperm from both species. Conversely, intracellular Ca(2+) concentration did not increase under these conditions in mouse epididymal or human epididymal sperm. Furthermore, pre-incubation with HCO(3)(–) triggered an intracellular Ca(2+) concentration increase in response to KCl in human epididymal sperm. Treatment with protein kinase A (PKA) inhibitors during exposure to HCO(3)(–) inhibited Ca(2+) concentration increases in mouse epididymal sperm and in both mouse and human ejaculated sperm. Finally, we show that soluble adenylyl cyclase and increased intracellular pH are required for the intracellular Ca(2+) concentration increase in both human and mouse sperm. In summary, our results suggest that a conserved mechanism of activation of CatSper channels is present in both human and mouse sperm. In this mechanism, HCO(3)(–) in semen activates the soluble adenylyl cyclase/protein kinase A pathway, which leads to increased intracellular pH and sensitizes CatSper channels to respond to membrane depolarization to allow Ca(2+) influx. This indirect mechanism of CatSper sensitization might be an early event capacitation that occurs as soon as the sperm contact the semen. Frontiers Media S.A. 2021-09-28 /pmc/articles/PMC8505895/ /pubmed/34650979 http://dx.doi.org/10.3389/fcell.2021.733653 Text en Copyright © 2021 Ferreira, Lybaert, Puga-Molina and Santi. https://creativecommons.org/licenses/by/4.0/This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
spellingShingle Cell and Developmental Biology
Ferreira, Juan J.
Lybaert, Pascale
Puga-Molina, Lis C.
Santi, Celia M.
Conserved Mechanism of Bicarbonate-Induced Sensitization of CatSper Channels in Human and Mouse Sperm
title Conserved Mechanism of Bicarbonate-Induced Sensitization of CatSper Channels in Human and Mouse Sperm
title_full Conserved Mechanism of Bicarbonate-Induced Sensitization of CatSper Channels in Human and Mouse Sperm
title_fullStr Conserved Mechanism of Bicarbonate-Induced Sensitization of CatSper Channels in Human and Mouse Sperm
title_full_unstemmed Conserved Mechanism of Bicarbonate-Induced Sensitization of CatSper Channels in Human and Mouse Sperm
title_short Conserved Mechanism of Bicarbonate-Induced Sensitization of CatSper Channels in Human and Mouse Sperm
title_sort conserved mechanism of bicarbonate-induced sensitization of catsper channels in human and mouse sperm
topic Cell and Developmental Biology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8505895/
https://www.ncbi.nlm.nih.gov/pubmed/34650979
http://dx.doi.org/10.3389/fcell.2021.733653
work_keys_str_mv AT ferreirajuanj conservedmechanismofbicarbonateinducedsensitizationofcatsperchannelsinhumanandmousesperm
AT lybaertpascale conservedmechanismofbicarbonateinducedsensitizationofcatsperchannelsinhumanandmousesperm
AT pugamolinalisc conservedmechanismofbicarbonateinducedsensitizationofcatsperchannelsinhumanandmousesperm
AT santiceliam conservedmechanismofbicarbonateinducedsensitizationofcatsperchannelsinhumanandmousesperm