Involvement of zinc in the regulation of pHi, motility, and acrosome reactions in sea urchin sperm.

Abstract

When sperm of Strongylocentrotus purpuratus or Lytechinus pictus are diluted into seawater, motility is initiated; and when exposed to egg jelly, an acrosome reaction is induced. In the presence of a variety of structurally different metal chelators (0.1-1 mM EDTA, EGTA, phenanthroline, dipyridyl, cysteine, or dithiothreitol), motility initiation is delayed and the acrosome reaction is inhibited. Of the metals detected in the sperm of these two species, very low levels of Zn +2 (0.1 /~M free Zn ÷z) uniquely prevent this chelator inhibition. L. pictus sperm concentrate 65Zn+2 from seawater, and EDTA removes 50% of the accumulated ~SZn+2 by 5 min. Since both sperm motility and acrosome reactions are in part regulated by intracellular pH (pHi), the effect of chelators on the sperm pH~ was examined by using the fluorescent pH sensitive probe, 9-aminoacridine. FDTA depresses sperm pH~ in both species, and 0.1 #M free Zn +2 reverses this pH~ depression. When sperm are diluted into media that contain chelators, both NH4CI and monensin (a Na+/H + ionophore) increase the sperm pH~ and reverse the chelator inhibition of sperm motility and acrosome reactions. The results of this study are consistent with the involvement of a trace metal (probably zinc) in the p14~ regulation of sea urchin sperm and indicate a likely mechanism for the previously observed effects of chelators on sperm motility and acrosome reactions.Sea urchin spermatozoa are immotile in semen. The motility that ensues upon dilution into seawater requires an elevation of intracellular pH (pHi)' (see references 1, 2, and 3) and is accompanied by increased cAMP levels (4, 5). The acrosome reaction (induced by egg jelly) involves increases in both pHi and intracellular Ca +2 as well as movements of Na ÷ and K + (6-9).Heavy metals are also somehow involved in sea urchin sperm motility and acrosome reactions. Metal chelators at concentrations that do not alter the Ca ÷2 or Mg +2 levels in the seawater prolong the fertilizable life of sea urchin spermatozoa (10, 11,12), and a recent investigation of this phenomenon showed that this prolongation of sperm motility by J Abbreviations used in this paper: 9AA, 9-aminoacridine, a fluorescent amine; ASW, artificial seawater formulation consisting of 423 mM NaC1.9 mM KCI, 9.27 mM CaC12, 22.94 mM MgC12, 25.5 mM MgSO4, 2.15 mM NaHCO~, and 10 mM Tris; EDTA-ASW, ASW to which 1 mM EDTA was added; OCaSW, ASW without CaC12; phi, intracellular pH.THE JOURNAL OF CELL BIOLOGY • VOLUME 100JUNE 1985 1817-1824 © The Rockefeller University Press • 0021-9525]85/05/1817/08 $ 1.00 metal chelators could be partially explained by a chelator inhibition of spontaneous (non-jelly initiated) acrosome reactions (12). It was also reported that these chelators would inhibit jelly-initiated acrosome reactions in the sperm of the sea urchin, Lytechinus pictus (12). Other reports have implicated Cu +2 and/or Zn ÷2 in the regulation of sea urchin sperm respiration and motility (13-18).We have now studied this effect of chelators on both sperm...

Increase in intracellular pH induces phosphorylation of axonemal proteins for activation of flagellar motility in starfish sperm

“…Sea urchin sperm are known to initiate their motility when suspended in seawater. According to Clapper et al (1985) The effect of histidine on the motility activation of flagella decreased at the end of the breeding season (data not shown), suggesting that there is an association of Zn 2+ with the maturity of sperm. The effect of EDTA also decreases with maturity in starfish Asterias amurensis (Mohri et al, 1990).…”

“…These results suggest (Christen et al, 1982;Lee et al, 1983;Lee, 1985). Zn 2+ is also involved in the regulation (Clapper et al, 1985), but the mechanism of action is different. Sea urchin sperm are known to initiate their motility when suspended in seawater.…”

Zinc is an essential trace element for spermatogenesis

“…Morisawa and Yoshida have also reported that Zn in the seminal plasma of human suppresses sperm motility, and that the removal of Zn by binding to a protein named semenogelin enhances motility (6). On the other hand, in sea urchin, treatment with the bivalent metal ion chelator, ethylenediamine tetra acetic acid (EDTA), inhibits sperm motility that is reversed by the addition of Zn (9). These results suggest that extracellular Zn indeed affects sperm motility but whether this is inhibitory or stimulatory appears to be species-specific.…”

Progression of Flagellar Stages during Artificially Delayed Motility Initiation in Sea Urchin Sperm

“…This solution, which will be referred to as KEG, substantially retards motility initiation in sea-urchin sperm cells as described later on. The idea of retardation by KEG is based on the facts that sea-urchin sperm remain quiescent in Na + -free seawater (Lee et al ., 1983;Bibring et al ., 1984;Schackmann et al ., 1984;Gatti and Christen, 1985;Christen et al ., 1986), and also immotile at elevated K + concentrations (Christen et al ., 1986;Bracho et al ., 1997) and become active when the intracellular pH is elevated, e.g., by addition of Na + or amine (Christen et al ., 1982;Lee et al ., 1983;Bibring et al ., 1984;Lee, 1984a, b;Bracho et al ., 1997), and that activation is, however, delayed in the presence of a variety of metal chelators including EDTA (Clapper et al ., 1985;Christen et al ., 1986). The KEG retardation of motility initiation first revealed distinct transient patterns of flagellar bending described in the present study.…”

“…Motility initiation involves the switching on of the sperm flagellar apparatus, which occurs simultaneously or successively, probably creating transient states of the axoneme with some mechanisms working but others being suppressed. Motility initiation, however, occurs instantaneously or so rapid that it is hard to capture such transients for analysis, when sperm are diluted in seawater (Clapper et al ., 1985;Dorsten et al ., 1997).…”