Identification of mouse trp homologs and lipid rafts from spermatogenic cells and sperm

Intracellular Ca2+ has an important regulatory role in the control of sperm motility, capacitation, and the acrosome reaction (AR). However, little is known about the molecular identity of the membrane systems that regulate C a2+ in sperm. In this report, we provide evidence for the expression of sev en Drosophila transient receptor potential homolog genes (trp1-7) and three of their protein products (Trp1, Trp3 and Trp6) in mouse sperm. Allegedly some trps encode capacitative Ca2+ channels. Immunoconfocal images showed t hat while Trp6 was present in the postacrosomal region and could be involve d in sperm AR, expression of Trp1 and Trp3 was confined to the flagellum, s uggesting that they may serve sperm to regulate important Ca2+-dependent ev ents in addition to the AR. Likewise, one of these proteins (Trp1) co-immun olocalized with caveolin-1, a major component of caveolae, a subset of lipi d rafts potentially important for signaling events and Ca2+ flux. Furthermo re, by using fluorescein-coupled cholera toxin B subunit, which specificall y binds to the raft component ganglioside GM1, we identified caveolin- and Trp-independent lipid rafts residing in the plasma membrane of mature sperm . Notably, the distribution of GM1 changes drastically upon completion of t he AR. (C) 2001 Published by Elsevier Science B.V. on behalf of the Federat ion of European Biochemical Societies.