185 TRANSIENT RECEPTOR POTENTIAL CHANNEL-2 (TRPP2) REGULATES MOTILITY AND INTRACELLULAR CALCIUM OF PORCINE SPERM

Abstract

Transient receptor potential channel-2 (TRPP2) is a membrane protein important for the regulation of calcium homeostasis in renal epithelial cells. Mutations in human TRPP2 cause enlarged cystic kidneys and contribute to polycystic kidney disease. In addition, TRPP2 functions have been described in some invertebrate sperm and are related to sperm-egg interactions and mating. Male Drosophila with mutated TRPP2 display a mild sperm motility phenotype but have a drastic reduction in fertility due to failed sperm migration and storage within the female tract. Although TRPP2 has critical roles for Drosophila sperm function, the protein has not been described in mammalian sperm. The TRPP2 mutations affecting sperm function could explain idiopathic subfertility that is not detected when evaluating sperm by routine analyses. Herein we report the location of TRPP2 in porcine sperm and have identified functions of TRPP2 in regulating sperm functions important for fertility. The TRPP2 was detected as a 110-kDa band in protein lysates from sperm after capacitation or mock incubation in conditions that do not capacitate sperm. With immunofluorescence, TRPP2 was most abundant on the head and principal piece of sperm with more consistent staining patterns when sperm were maintained in non-capacitating medium. Inhibition of TRPP2 by antiserum resulted in a reduction in sperm average path and curvilinear velocity and an increase in tail cross-beat frequency when sperm were incubated in capacitating conditions. Sperm incubated with TRPP2 antiserum also had a significant decrease in intracellular calcium concentration compared with control samples and failed to undergo an increase in calcium over 90 min that is characteristic of capacitating sperm. TRPP2 is a previously unreported mammalian sperm membrane protein that appears to function as an ion channel to regulate calcium and capacitation-like changes in porcine sperm.

This project is supported by Agriculture and Food Research Initiative Competitive Grant no. 2011–67015–20099 and 2015–67015–23228 from the USDA National Institute of Food and Agriculture.