7: Mol Hum Reprod. 2003 Mar;9(3):125-31.  
Role of protein tyrosine phosphorylation in the thapsigargin-induced intracellular Ca(2+) store depletion during human sperm acrosome reaction.

Dorval V, Dufour M, Leclerc P.

Departement d'Obstetrique/Gynecologie and Centre de recherche en Biologie de la Reproduction, Universite Laval, and Centre de recherche du CHUQ, Quebec, G1L 3L5 and.

During human sperm capacitation, an increase in phosphotyrosine content of specific proteins results partially from an increase in the intracellular free Ca(2+) concentrations. In the present study, the inter-regulation between protein phosphotyrosine content and the intracellular Ca(2+) concentration during the thapsigargin treatment of capacitated human sperm was investigated. The involvement of a tyrosine kinase pathway in the thapsigargin-induced acrosome reaction was also investigated. In response to thapsigargin, two sperm subpopulations, called LR (low responsive) and HR (high responsive), according to their increase in intracellular Ca(2+), were observed. In addition to their high increase in intracellular Ca(2+), sperm from the HR population expressed a higher protein phosphotyrosine content, and a higher proportion (P < 0.05) of them underwent the acrosome reaction in response to thapsigargin, as compared with LR sperm. Although the tyrosine kinase inhibitor PP2 abolished the thapsigargin-induced increase in protein phosphotyrosine content, it did not affect the intracellular Ca( 2+) concentration or the percentage of acrosome-reacted sperm. The inability of an src-related tyrosine kinase inhibitor to block the thapsigargin-mediated Ca(2+) increase and acrosomal exocytosis suggests that, during the acrosome reaction, the signalling pathway mediated by src-related tyrosine kinases is involved upstream of the capacitative Ca(2+) entry.

PMID: 12606588 [PubMed - in process]




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