Participation of the sperm proteasome in human fertilization

Author： Morales Patricio Kong Milene Pizarro Eduardo Pasten Consuelo

ISSN： 1460-2350

Source： Human Reproduction, Vol.18, Iss.5, 2003-05, pp. : 1010-1017

Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.

Previous Menu Next

Abstract

BACKGROUND: Fertilization in mammals comprises the sequential interactions of the sperm with the cumulus oophorus, zona pellucida, and oocyte plasma membrane. Here we investigate proteasome activity in human sperm and its possible involvement during the fertilization process. METHODS: Proteasome activity was measured in intact sperm and in sperm extracts using the fluorogenic substrate Suc‐Leu‐Leu‐Val‐Tyr‐AMC, in the presence or absence of the specific proteasome inhibitor, clasto‐lactacystin ‐lactone. The participation of the proteasome was evaluated during (i) sperm–zona binding using the hemizona assay; (ii) zona pellucida‐induced acrosome reactions with a pulse and chase design; (iii) progesterone‐induced acrosome reactions incubating overnight capacitated sperm with progesterone; and (iv) progesterone‐induced Ca²⁺ influx using fura‐2AM. RESULTS: Intact sperm and sperm extracts possessed proteasome activity, which was susceptible to inhibition by clasto‐lactacystin ‐lactone. Sperm–zona binding was not inhibited by clasto‐lactacystin ‐lactone. However, both zona pellucida‐ and progesterone‐induced acrosome reactions were inhibited by clasto‐lactacystin ‐lactone. The proteasome inhibitor also blocked the sustained phase of the Ca²⁺ influx provoked by progesterone but not the peak. CONCLUSION: The human sperm proteasome is involved in the exocytosis of the acrosome, perhaps in events upstream of the plateau phase of the Ca²⁺ influx.