Regulation of Protein Tyrosine Phosphorylation in Human Sperm by a calcium/calmodulin-dependent Mechanism: Identification of A Kinase Anchor Proteins as Major Substrates for Tyrosine Phosphorylation

Dev Biol. 1996 Nov 25;180(1):284-96. doi: 10.1006/dbio.1996.0301.

Abstract

Signal transduction pathways regulate various aspects of mammalian sperm function. When human sperm were incubated in a medium supporting capacitation, proteins became tyrosine-phosphorylated in a time-dependent manner. This phosphorylation was inhibited by genistein, a protein tyrosine kinase inhibitor. Phosphorylation was also reduced when sperm were incubated either in the presence of increasing concentrations of extracellular Ca2+ or in a medium containing the Ca2+ ionophore A23187. This Ca2+-induced dephosphorylation was calmodulin-dependent, suggesting that calcineurin was involved. In this regard, the calcineurin inhibitor deltamethrin inhibited the Ca2+ ionophore-induced dephosphorylation. A limited number of Mr 80,000-105,000 polypeptides were the most prominent phosphotyrosine-containing proteins present in human sperm. Unlike mouse sperm, which contains a tyrosine-phosphorylated isoform of hexokinase, a phosphotyrosine-containing hexokinase in human sperm was not detected. Most of the tyrosine-phosphorylated proteins were Triton X-100-insoluble and were localized to the principal piece of the flagellum, the region where the cytoskeletal fibrous sheath is found. Prominent phosphotyrosine-containing proteins of Mr 82,000 and 97,000 were identified as the human homologues of mouse sperm AKAP82, the major fibrous sheath protein, and pro-AKAP82, its precursor polypeptide, respectively. These proteins are A Kinase Anchor Proteins, polypeptides that sequester protein kinase A to subcellular locations. Taken together, these results suggest that protein tyrosine phosphorylation may be part of a signal transduction cascade(s) regulating events pertaining to capacitation and/or motility in mammalian sperm and that an interrelationship between tyrosine kinase and cAMP signaling pathways exists in these cells.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alkaloids
  • Animals
  • Benzophenanthridines
  • Calcimycin / pharmacology
  • Calcium / metabolism*
  • Calmodulin / metabolism*
  • Cyclic AMP-Dependent Protein Kinases / metabolism*
  • Enzyme Inhibitors / pharmacology
  • Genistein
  • Humans
  • Isoflavones / pharmacology
  • Male
  • Mice
  • Phenanthridines / pharmacology
  • Phosphorylation
  • Phosphotyrosine / analysis
  • Phosphotyrosine / metabolism*
  • Protein Kinase Inhibitors
  • Proteins / metabolism*
  • Seminal Plasma Proteins*
  • Spermatozoa / drug effects
  • Spermatozoa / metabolism*
  • Staurosporine / pharmacology

Substances

  • Alkaloids
  • Benzophenanthridines
  • Calmodulin
  • Enzyme Inhibitors
  • Isoflavones
  • Phenanthridines
  • Protein Kinase Inhibitors
  • Proteins
  • Seminal Plasma Proteins
  • Phosphotyrosine
  • Calcimycin
  • Genistein
  • chelerythrine
  • Cyclic AMP-Dependent Protein Kinases
  • Staurosporine
  • Calcium