Sperm-activating peptides in the regulation of ion fluxes, signal transduction and motility

Abstract

Echinoderm sperm use cyclic nucleotides (CNs) as essential second messengers to locate and swim towards the egg. Sea urchin sperm constitute a rich source of membrane-bound guanylyl cyclase (mGC), which was first cloned from sea urchin testis by the group of David Garbers. His group also identified speract, the first sperm-activating peptide (SAP) to be isolated

Single cell imaging reveals that the motility regulator speract induces a flagellar alkalinization that precedes and is independent of Ca2+ influx in sea urchin spermatozoa

“…Speract binds to its receptor stimulating cGMP synthesis, and this nucleotide activates a K + -selective cyclic nucleotide dependent channel (tetraKCNG) causing a membrane potential hyperpolarization that has been proposed to increase intracellular pH (pHi) and Ca 2+ concentration ([Ca 2+ ]i) (reviewed in [1]). Speract induces [Ca 2+ ]i oscillations that modulate flagellar beating and sperm swimming [2,3].…”

Niflumic acid disrupts marine spermatozoan chemotaxis without impairing the spatiotemporal detection of chemoattractant gradients

“…It has been proposed that spermatozoa swimming up a positive chemoattractant gradient will experience increasing rates of chemoattractant binding and receptor activation, leading to sustained membrane hyperpolarization due to the opening of KCNG channels. This hyperpolarized state is sustained until spermatozoa enter negative chemoattractant gradients, at which point the membrane depolarizes leading to the opening of CaV channels (Guerrero et al, 2010a;Darszon et al, 2008;Bönigk et al, 2009;Strünker et al, 2006;Guerrero et al, 2010b;Galindo et al, 2007;Cook et al, 1994). We found that NFA does not apparently perturb this putative chemoattractant gradient decoding mechanism, indicating that the molecular targets of NFA are downstream of the components regulating the initial Ca 2+ burst.…”

“…sperm membrane potential releases CaV channels from inactivation, and stimulates the activity of HCN channels (Darszon et al, 2008). The opening of HCN channels repolarizes V m , leading to opening of CaV channels.…”

“…The decapeptide speract (GFDLNGGGVG) is one of the most widely studied members of the sperm-activating peptide family that modulate sea urchin sperm motility (Suzuki, 1995) (reviewed in Darszon et al, 2008). This peptide, purified from Strongylocentrotus purpuratus eggs, also cross-reacts with spermatozoa from Lytechinus pictus sea urchins (Hansbrough and Garbers, 1981;Suzuki et al, 1981;Suzuki and Garbers, 1984).…”

Black Tea High-Molecular-Weight Polyphenol Increases the Motility of Sea Urchin Sperm by Activating Mitochondrial Respiration

“…7,8) SAPs increase sperm motility and mitochondrial respiration, and the molecular mechanisms underlying their activation have been well studied. 6) Here, we treated sea urchin sperm with egg seawater (ESW) containing SAPs as positive control for sperm activation, and evaluated the effects of MAF by comparing them with known effects of ESW. Preparation of ESW was as follows: sea urchin eggs were washed with artificial sea water (ASW, 262 mM NaCl, 9 mM KCl, 10 mM CaCl 2 , 48 mM MgCl 2 , 10 mM Hepes, pH 8.0), suspended in 5 mL of ASW, and incubated for 1 h. The concentration of eggs in the suspension was 8:4 Â 10 5 cells/mL.…”