Expression and differential cell distribution of low-threshold Ca(2+) channels in mammalian male germ cells and sperm.
Numerous sperm functions including the acrosome reaction (AR) are associated with Ca(2+) influx through voltage-gated Ca(2+) (Ca(V)) channels. Although the electrophysiological characterization of Ca(2+) currents in mature sperm has proven difficult, functional studies have revealed the presence of low-threshold (Ca(V)3) channels in spermatogenic cells. However, the molecular identity of these proteins remains undefined. Here, we identified by reverse transcription polymerase chain reaction the expression of Ca(V)3.3 mRNA in mouse male germ cells, an isoform not previously described in these cells. Immunoconfocal microscopy revealed the presence of the three Ca(V)3 channel isoforms in mouse spermatogenic cells. In mature mouse sperm only Ca(V)3.1 and Ca(V)3.2 were detected in the head, suggesting its participation in the AR. Ca(V)3.1 and Ca(V)3.3 were found in the principal and the midpiece of the flagella. All Ca(V)3 channels are also present in human sperm, but only to a minor extent in the head. These findings were corroborated by immunogold transmission electron microscopy. Tail localization of Ca(V)3 channels suggested they may participate in motility, however, mibefradil and gossypol concentrations that inhibit Ca(V)3 channels did not significantly affect human sperm motility. Only higher mibefradil doses that can block high-threshold (HVA) Ca(V) channels caused small but significant motility alterations. Antibodies to HVA channels detected Ca(V)1.3 and Ca(V)2.3 in human sperm flagella.
Treviño
Claudia L
CL
Department of Genetics of Development and Molecular Physiology, Institute of Biotechnology, UNAM, Avenida Universidad #2001, Col. Chamilpa, CP 62210, Cuernavaca, Mor., Mexico.
Felix
Ricardo
R
Castellano
Laura E
LE
Gutiérrez
Carolina
C
Rodríguez
Delany
D
Pacheco
Judith
J
López-González
Ignacio
I
Gomora
Juan Carlos
JC
Tsutsumi
Victor
V
Hernández-Cruz
Arturo
A
Fiordelisio
Tatiana
T
Scaling
Allison L
AL
Darszon
Alberto
A
D000818:Animals; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020747:Calcium Channels, T-Type / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D019084:Fluorescent Antibody Technique, Indirect; D005854:Germ Cells / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D006801:Humans; D015640:Ion Channel Gating / Q000502:physiology; D008297:Male; D020748:Mibefradil / Q000494:pharmacology; D051379:Mice; D008815:Mice, Inbred Strains; D018408:Patch-Clamp Techniques; D016133:Polymerase Chain Reaction; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D013081:Sperm Motility / Q000187:drug effects; D013094:Spermatozoa / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure
D002121:Calcium Channel Blockers; D020747:Calcium Channels, T-Type; D020033:Protein Isoforms; D012333:RNA, Messenger; D020748:Mibefradil