title: 2-APB-potentiated channels amplify CatSper-induced Ca(2+) signals in human sperm.
abstract: Ca2+i signalling is pivotal to sperm function. Progesterone, the best-characterized agonist of human sperm Ca2+i signalling, stimulates a biphasic [Ca2+]i rise, comprising a transient and subsequent sustained phase. In accordance with recent reports that progesterone directly activates CatSper, the [Ca2+]i transient was detectable in the anterior flagellum (where CatSper is expressed) 1-2 s before responses in the head and neck. Pre-treatment with 5 μM 2-APB (2-aminoethoxydiphenyl borate), which enhances activity of store-operated channel proteins (Orai) by facilitating interaction with their activator [STIM (stromal interaction molecule)] 'amplified' progesterone-induced [Ca2+]i transients at the sperm neck/midpiece without modifying kinetics. The flagellar [Ca2+]i response was unchanged. 2-APB (5 μM) also enhanced the sustained response in the midpiece, possibly reflecting mitochondrial Ca2+ accumulation downstream of the potentiated [Ca2+]i transient. Pre-treatment with 50-100 μM 2-APB failed to potentiate the transient and suppressed sustained [Ca2+]i elevation. When applied during the [Ca2+]i plateau, 50-100 μM 2-APB caused a transient fall in [Ca2+]i, which then recovered despite the continued presence of 2-APB. Loperamide (a chemically different store-operated channel agonist) enhanced the progesterone-induced [Ca2+]i signal and potentiated progesterone-induced hyperactivated motility. Neither 2-APB nor loperamide raised pHi (which would activate CatSper) and both compounds inhibited CatSper currents. STIM and Orai were detected and localized primarily to the neck/midpiece and acrosome where Ca2+ stores are present and the effects of 2-APB are focussed, but store-operated currents could not be detected in human sperm. We propose that 2-APB-sensitive channels amplify [Ca2+]i elevation induced by progesterone (and other CatSper agonists), amplifying, propagating and providing spatio-temporal complexity in [Ca2+]i signals of human sperm.
authors.affiliation: Medical School, University of Birmingham, Birmingham B15 2TT, UK.
authors.forename: Linda
authors.initials: L
authors.lastname: Lefièvre
authors.forename: Katherine
authors.initials: K
authors.lastname: Nash
authors.forename: Steven
authors.initials: S
authors.lastname: Mansell
authors.forename: Sarah
authors.initials: S
authors.lastname: Costello
authors.forename: Emma
authors.initials: E
authors.lastname: Punt
authors.forename: Joao
authors.initials: J
authors.lastname: Correia
authors.forename: Jennifer
authors.initials: J
authors.lastname: Morris
authors.forename: Jackson
authors.initials: J
authors.lastname: Kirkman-Brown
authors.forename: Stuart M
authors.initials: SM
authors.lastname: Wilson
authors.forename: Christopher L R
authors.initials: CL
authors.lastname: Barratt
authors.forename: Stephen
authors.initials: S
authors.lastname: Publicover
mesh_terms: D001896:Boron Compounds / Q000494:pharmacology*; D002120:Calcium Channel Agonists / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects*; D015815:Cell Adhesion Molecules / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008139:Loperamide / Q000494:pharmacology; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D009363:Neoplasm Proteins / Q000378:metabolism; D000071740:ORAI1 Protein; D000071741:ORAI2 Protein; D011374:Progesterone / Q000494:pharmacology; D032961:Sperm Midpiece / Q000187:drug effects / Q000378:metabolism; D013081:Sperm Motility / Q000187:drug effects; D013094:Spermatozoa / Q000187:drug effects* / Q000378:metabolism*; D000071737:Stromal Interaction Molecule 1; D000071738:Stromal Interaction Molecule 2
chemical_list: D001896:Boron Compounds; C438823:CATSPER1 protein, human; D002120:Calcium Channel Agonists; D015220:Calcium Channels; D015815:Cell Adhesion Molecules; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D000071740:ORAI1 Protein; C510746:ORAI1 protein, human; D000071741:ORAI2 Protein; C514506:ORAI2 protein, human; C522867:Orai3 protein, human; C103530:STIM1 protein, human; C513279:STIM2 protein, human; D000071737:Stromal Interaction Molecule 1; D000071738:Stromal Interaction Molecule 2; D011374:Progesterone; D008139:Loperamide; C109986:2-aminoethoxydiphenyl borate