Role of OMC32 Polypeptide in Acrosin-Mediated Exocytosis during the Bovine Sperm Acrosome Reaction

Authors: Nagdas SK* , Salters T , Sharpe B and Donald D

DOI: 10.23880/ijbp-16000268

Volume 10, Issue 2

Abstract

Acrosome reaction (AR) is a major controlling step in the mammalian fertilization. Failure or improper AR is one of the reasons of infertility. Numerous unresolved questions remain regarding signaling events and biochemical mechanisms promoting the membrane fusion of the mammalian sperm AR. Previously, we characterized an acrosomal matrix component from the acrosome named the outer acrosomal membrane-associated matrix complex (OMC), consist of three major (54, 50, and 45kDa) and several minor (38-19kDa) polypeptides, termed “rpf”. A 32kDa polypeptide (OMC32) was characterized from the “rpf” polypeptides. The present study demonstrates that OMC32 is present in one large complex within the acrosomal matrix and there is a physiological interaction between OMC 32 and IZUMO1/SPACA3 polypeptides of bovine sperm acrosome. We have shown that there is a significant release of SPACA3 during lysophosphatidyl choline-induced acrosome reaction and SPACA3 was not released in the presence of acrosin inhibitors. This study reveals that acrosin involves in the release of SPACA3 during acrosome exocytosis. To describe the function of OMC32 polypeptide, Fab fragments prepared from the IgG fractions of anti- OMC32 were utilized and the inhibition of acrosomal exocytosis was examined using the release of acrosin as a potential marker. The inhibition of acrosin release was observed in the presence of 10μg Fab fragments. Our established permeabilizedcell protocol for exocytosis strongly reveals that OMC32 plays a significant role in the regulation of acrosin release during acrosomal exocytosis. This study exhibits the role of acrosomal hydrolases and matrix proteins in mammalian fertilization.

Keywords: Bovine Sperm; Epididymis; Sperm Permeabilization; Acrosomal Protein; Acrosome Reaction

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