A sperm-activating peptide controls a cGMP-signaling pathway in starfish sperm☆

Abstract

Peptides released from eggs of marine invertebrates play a central role in fertilization. About 80 different peptides from various phyla have been isolated, however, with one exception, their respective receptors on the sperm surface have not been unequivocally identified and the pertinent signaling pathways remain ill defined. Using rapid mixing techniques and novel membrane-permeable caged compounds of cyclic nucleotides, we show that the sperm-activating peptide asterosap evokes a fast and transient increase of the cGMP concentration in sperm of the starfish Asterias amurensis, followed by a transient cGMP-stimulated increase in the Ca(2+) concentration. In contrast, cAMP levels did not change significantly and the Ca(2+) response evoked by photolysis of caged cAMP was significantly smaller than that using caged cGMP. By cloning of cDNA and chemical crosslinking, we identified a receptor-type guanylyl cyclase in the sperm flagellum as the asterosap-binding protein. Sperm respond exquisitely sensitive to picomolar concentrations of asterosap, suggesting that the peptide serves a chemosensory function like resact, a peptide involved in chemotaxis of sperm of the sea urchin Arbacia punctulata. A unifying principle emerges that chemosensory transduction in sperm of marine invertebrates uses cGMP as the primary messenger, although there may be variations in the detail.

Identification of Guanylate Cyclases and Related Signaling Proteins in Sperm Tail from Sea Stars by Mass Spectrometry

“…Asterosap binds to the guanylate cyclase extracellular domain and activates its intracellular catalytic domain to produce cGMP. Increased intracellular cGMP leads events such as membrane hyperpolarization and increases in intracellular Ca 2+ and pH as reported (Matsumoto et al 2003;Kawase et al 2005). Candidate membrane proteins responsible for these events are the K + channel, the K + -dependent Na + /Ca 2+ exchanger (NCKX in Figure 2; Islam et al 2006), and the Na + /H + exchanger (NHE in Figure 2).…”

“…The membrane-bound guanylate cyclase has been identified with a high score in sperm tail of each sea star species examined (Table S1 for A. forbesi), indicating its Table S1. significant abundance in the sperm tail (Matsumoto et al 2003). The abundance of guanylate cyclase may be required to allow the sperm to persist in chemotaxis, receiving signaling molecules one by one until reaching the egg.…”

“…In this process, the asterosap functions as a chemoattractant to the sperm. The asterosap receptor, a membranebound guanylate cyclase, is specifically located in the sperm tail (Matsumoto et al 2003;Shiba et al 2006). The asterosap receptor has four structural domains including the extracellular domain receiving the asterosap, the transmembrane domain transmitting signals from the outside to the inside of the cell, the kinase-like domain having dephosphorylation upon stimulation from the outside, and the guanylate cyclase domain transmitting the secondary messenger, cyclic guanosine monophosphate (cGMP).…”

Sea urchin fertilization in a warm, acidified and high pCO2 ocean across a range of sperm densities

“…The inhibitory effect of low pH on sperm motility is over ridden in nature by the respiratory dilution effect of seawater (increased oxygen tension) and by the egg jelly peptides that promote sperm motility at low pH (Brokaw, 1990;Chia and Bickell, 1983;Darszon et al, 2008;Ward et al, 1985). This mechanism appears to be common in marine invertebrates and likely to involve similar cGMP messenger systems (Darszon et al, 2008;Hoshi et al, 1994;Matsumoto et al, 2003). (Havenhand et al, 2008).…”

Control of the Yeast Cell Cycle with a Photocleavable α‐Factor Analogue

“…Although caging of bioactive molecules for subsequent activation by using UV light is a common strategy, [6][7][8][9][10][11] the use of photocleavable functionality for deactivation of peptides and proteins [12] is relatively unexplored. Backbone cleavage through 2-nitrophenyl amino acid derivatives provides an interesting way to specifically turn off a biological signal of interest.…”