The sperm surface localization of the TRP-3/SPE-41 Ca2+-permeable channel depends on SPE-38 function in Caenorhabditis elegans

Abstract

Despite undergoing normal development and acquiring normal morphology and motility, mutations in spe-38 or trp-3/spe-41 cause identical phenotypes in Caenorhabditis elegans – mutant sperm fail to fertilize oocytes despite direct contact. SPE-38 is a novel, four-pass transmembrane protein and TRP-3/SPE-41 is a Ca2+-permeable channel. Localization of both of these proteins is confined to the membranous organelles (MOs) in undifferentiated spermatids. In mature spermatozoa, SPE-38 is localized to the pseudopod and TRP-3/SPE-41 is localized to the whole plasma membrane. Here we show that the dynamic redistribution of TRP-3/SPE-41 from MOs to the plasma membrane is dependent on SPE-38. In spe-38 mutant spermatozoa, TRP-3/SPE-41 is trapped within the MOs and fails to reach the cell surface despite MO fusion with the plasma membrane. Split-ubiquitin yeast-two-hybrid analyses revealed that the cell surface localization of TRP-3/SPE-41 is likely regulated by SPE-38 through a direct protein-protein interaction mechanism. We have identified sequences that influence the physical interaction between SPE-38 and TRP-3/SPE-41, and show that these sequences in SPE-38 are required for fertility in transgenic animals. Despite the mislocalization of TRP-3/SPE-41 in spe-38 mutant spermatozoa, ionomycin or thapsigargin induced influx of Ca2+ remains unperturbed. This work reveals a new paradigm for the regulated surface localization of a Ca2+-permeable channel.

Thermosensitive ion channel TRPV1 is endogenously expressed in the sperm of a fresh water teleost fish (Labeo rohita) and regulates sperm motility

“…42,43 In Drosophila, a polycystin-2 homolog channel localized in flagella and is required for male fertility. 44 Our results are in full agreement with the previous reports, which demonstrated that temperature is an important regulatory factor for maturation and motility in fish sperm cells. [45][46][47] Indeed it is known that carp sperms take more time for acquiring motility when incubated in cold water (15°C) vs. warm water (20°C).…”

Meeting report – Oocyte maturation and fertilization: lessons from canonical and emerging models

“…Andrew Singson talked about the spe-38 mutant they obtained that cannot enter the oocyte despite direct contact. Based on analysis of the mutant, he identified SPE-38 as a transmembrane protein that interacts with the Ca 2+ -permeable channel TRP-3/SPE41 and regulates its localization (Singaravelu et al, 2012). This work will enable to better understand sperm-oocyte interactions and could complement fertility research in other species.…”

Functional Roles of spe Genes in the Male Germline During Reproduction of Caenorhabditis elegans

“…SPE-38 is probably involved in sperm-oocyte interactions because it localizes to pseudopods as does SPE-9. Recently, this protein was found to associate with SPE-41/ TRP-3 to regulate the SPE-41/TRP-3 localization (Singaravelu et al 2012 ). (Fig.…”