Participation of a K(+) channel modulated directly by cGMP in the speract-induced signaling cascade of strongylocentrotus purpuratus sea urchin sperm

Dev Biol. 2000 May 15;221(2):285-94. doi: 10.1006/dbio.2000.9678.


Speract, a decapeptide from Strongylocentrotus purpuratus sea urchin eggs, transiently stimulates a membrane guanylyl cyclase and activates a K(+)-selective channel that hyperpolarizes sperm. However, previous studies of sperm and of sperm membrane vesicles reached conflicting conclusions about the mechanisms that open these channels. We find that speract hyperpolarizes and increases the cGMP content of flagellar vesicles. We confirm previous findings that intravesicular GTPgammaS and GTP enhance this hyperpolarization, but not GDPbetaS. The G protein activators AlF(-)(4) and mastoparan also are ineffective. Thus, it is unlikely that a G protein participates in the speract response. In contrast, hyperpolarization responses to speract are increased by 3-isobutyl-1-methylxanthine, which preferentially inhibits cGMP-selective phosphodiesterases of sperm, and the 8Br-cGMP derivative hyperpolarizes vesicles in the absence of speract. The responses to speract and to 8Br-cGMP have similar ionic selectivities (K(+) > Rb(+) > > Li(+) > Na(+)) and sensitivities to the channel blockers 4-aminopiridine and 3, 4-dichlorobenzamil, indicating that they likely result from opening of the same K(+) channel. Inhibitors that preferentially inhibit cAMP-selective phosphodiesterases do not alter responses to speract, and permeant cAMP analogs do not hyperpolarize vesicles. In addition, inhibitors of protein kinases and phosphatases fail to alter vesicle hyperpolarization by speract. The increase in vesicular cGMP content produced by speract therefore may directly mediate opening of the channel that hyperpolarizes sperm membrane vesicles. Similar mechanisms presumably operate in intact sperm.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 4-Aminopyridine / pharmacology
  • Amiloride / analogs & derivatives
  • Amiloride / pharmacology
  • Animals
  • Cations, Monovalent / pharmacology
  • Cell Membrane / physiology
  • Cyclic GMP / analogs & derivatives
  • Cyclic GMP / pharmacology
  • Cyclic GMP / physiology*
  • Enzyme Inhibitors / pharmacology
  • GTP-Binding Proteins / physiology
  • Guanosine Diphosphate / analogs & derivatives
  • Guanosine Diphosphate / pharmacology
  • Male
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Oligopeptides / pharmacology
  • Oligopeptides / physiology*
  • Phosphoprotein Phosphatases / antagonists & inhibitors
  • Potassium Channel Blockers
  • Potassium Channels / physiology*
  • Protein Kinase Inhibitors
  • Sea Urchins
  • Signal Transduction / physiology*
  • Sperm Tail / physiology
  • Spermatozoa / physiology*
  • Thionucleotides / pharmacology


  • Cations, Monovalent
  • Enzyme Inhibitors
  • Oligopeptides
  • Potassium Channel Blockers
  • Potassium Channels
  • Protein Kinase Inhibitors
  • Thionucleotides
  • 3',4'-dichlorobenzamil
  • Guanosine Diphosphate
  • 8-bromocyclic GMP
  • guanosine 5'-O-(2-thiodiphosphate)
  • speract
  • Amiloride
  • 4-Aminopyridine
  • Phosphoprotein Phosphatases
  • GTP-Binding Proteins
  • Cyclic GMP