title: Cell-penetrating peptides, targeting the regulation of store-operated channels, slow decay of the progesterone-induced [Ca2+]i signal in human sperm.
abstract: Previous work has provided evidence for involvement of store-operated channels (SOCs) in [Ca(2+)]i signalling of human sperm, including a contribution to the transient [Ca(2+)]i elevation that occurs upon activation of CatSper, a sperm-specific cation channel localized to the flagellum, by progesterone. To further investigate the potential involvement of SOCs in the generation of [Ca(2+)]i signals in human sperm, we have used cell-penetrating peptides containing the important basic sequence KIKKK, part of the STIM-Orai activating region/CRAC activating domain (SOAR/CAD) of the regulatory protein stromal interaction molecule 1. SOAR/CAD plays a key role in controlling the opening of SOCs, which occurs upon mobilization of stored Ca(2+). Resting [Ca(2+)]i temporarily decreased upon application of KIKKK peptide (3-4 min), but scrambled KIKKK peptide had a similar effect, indicating that this action was not sequence-specific. However, in cells pretreated with KIKKK, the transient [Ca(2+)]i elevation induced by stimulation with progesterone decayed significantly more slowly than in parallel controls and in cells pretreated with scrambled KIKKK peptide. Examination of single-cell responses showed that this effect was due, at least in part, to an increase in the proportion of cells in which the initial transient was maintained for an extended period, lasting up to 10 min in a subpopulation of cells. We hypothesize that SOCs contribute to the progesterone-induced [Ca(2+)]i transient, and that interference with the regulatory mechanisms of SOC delays their closure, causing a prolongation of the [Ca(2+)]i transient.
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Morris
authors.affiliation: Molecular Pharmacology Research Group, Research Institute in Healthcare Science, University of Wolverhampton, Wolverhampton WV1 1LY, UK.
authors.forename: Sarah
authors.initials: S
authors.lastname: Jones
authors.affiliation: Molecular Pharmacology Research Group, Research Institute in Healthcare Science, University of Wolverhampton, Wolverhampton WV1 1LY, UK.
authors.forename: John
authors.initials: J
authors.lastname: Howl
authors.affiliation: Molecular Pharmacology Research Group, Research Institute in Healthcare Science, University of Wolverhampton, Wolverhampton WV1 1LY, UK.
authors.forename: Monika
authors.initials: M
authors.lastname: Lukanowska
authors.affiliation: The Medical School, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
authors.forename: Linda
authors.initials: L
authors.lastname: Lefievre
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK s.j.publicover@bham.ac.uk.
authors.forename: Stephen
authors.initials: S
authors.lastname: Publicover
mesh_terms: D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects*; D057846:Cell-Penetrating Peptides / Q000494:pharmacology*; D006801:Humans; D008297:Male; D011374:Progesterone / Q000494:pharmacology*; D013094:Spermatozoa / Q000187:drug effects* / Q000378:metabolism
chemical_list: D015220:Calcium Channels; D057846:Cell-Penetrating Peptides; D011374:Progesterone; D002118:Calcium
keywords: cell-penetrating peptide; spermatozoa; store-operated channels; stromal interaction molecule 1