Requirement of protein tyrosine kinase and phosphatase activities for human sperm exocytosis

C. N. Tomes, C. M. Roggero, G. De Blas, P. M. Saling, L. S. Mayorga

Research output: Contribution to journalArticlepeer-review

54 Scopus citations


The acrosome is a membrane-limited granule that overlies the nucleus of the mature spermatozoon. In response to physiological or pharmacological stimuli, sperm undergo calcium-dependent exocytosis termed the acrosome reaction, which is an absolute prerequisite for fertilization. Protein tyrosine phosphorylation and dephosphorylation are a mechanisms by which multiple cellular events are regulated. Here we report that calcium induces tyrosine phosphorylation in streptolysin O (SLO)-permeabilized human sperm. As expected, pretreatment with tyrphostin A47 - a tyrosine kinase inhibitor - abolishes the calcium effect. Interestingly, the calcium-induced increase in tyrosine phosphorylation has a functional correlate in sperm exocytosis. Masking of phosphotyrosyl groups with a specific antibody or inhibition of tyrosine kinases with genistein, tyrphostin A47, and tyrphostin A51 prevent the acrosome reaction. By reversibly sequestering intra-acrosomal calcium with a photo-inhibitable chelator, we show a requirement for protein tyrosine phosphorylation late in the exocytotic pathway, after the efflux of intra-acrosomal calcium. Both mouse and human sperm contain highly active tyrosine phosphatases. Importantly, this activity declines when sperm are incubated under capacitating conditions. Inhibition of tyrosine phosphatases with pervanadate, bis(N,N-dimethylhydroxoamido)hydroxovanadate, ethyl-3,4-dephostatin, and phenylarsine oxide prevents the acrosome reaction. Our results show that both tyrosine kinases and phosphatases play a central role in sperm exocytosis.

Original languageEnglish (US)
Pages (from-to)399-415
Number of pages17
JournalDevelopmental Biology
Issue number2
StatePublished - Jan 15 2004
Externally publishedYes


  • Acrosome reaction
  • Calcium
  • Capacitation
  • Exocytosis
  • Fusion
  • Kinase
  • Phosphatase
  • Sperm
  • Tyrosine phosphorylation

ASJC Scopus subject areas

  • Molecular Biology
  • Developmental Biology
  • Cell Biology


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