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Enzymatic activity of sperm proprotein convertase is important for mammalian fertilization
Author(s) -
Iamsaard Sitthichai,
Vanichviriyakit Rapeepun,
Hommalai Greanggrai,
Saewu Arpornrad,
Srakaew Nopparat,
Withyachumnarnkul Boonsirm,
Basak Ajoy,
Tanphaichitr gnuj
Publication year - 2011
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.22626
Subject(s) - sperm , capacitation , acrosome reaction , human fertilization , acrosome , biology , andrology , zona pellucida , epididymis , subtilisin , chemistry , enzyme , microbiology and biotechnology , biochemistry , oocyte , botany , anatomy , embryo , medicine
Proprotein convertase subtilisin/kexin 4 (PCSK4) is implicated for sperm fertilizing ability, based on studies using Pcsk4‐ null mice. Herein we demonstrated proprotein convertase (PC) activity in intact sperm and acrosomal vesicles. To determine whether this activity was important for sperm fertilizing ability, a peptide inhibitor was designed based on PCSK4 prodomain sequence (proPC4 75–90 ), which contains its primary autocatalytic cleavage site. ProPC4 75–90 inhibited recombinant PCSK4's activity with a K i value of 5.4 µM, and at 500 µM, it inhibited sperm PC activity almost completely. Treatment of sperm with proPC4 75–90 inhibited their egg fertilizing ability in a dose dependent manner. Correlation between sperm PC activity and fertilizing ability showed a high co‐efficient value (>0.9), indicating the importance of sperm PC activity in fertilization. In particular, sperm PC activity was important for capacitation and zona pellucida (ZP)‐induced acrosome reaction, since proPC4 75–90 ‐treated sperm showed markedly decreased rates in these two events. These results were opposite to those observed in Pcsk4‐ null sperm, which contained higher PC activity than wild type sperm, possibly due to overcompensation by PCSK7, the other PCSK enzyme found in sperm. ADAM2 (45 kDa), a sperm plasma membrane protein, involved in sperm–egg plasma membrane interaction, was also processed into a smaller form (27 kDa) during capacitation at a much reduced level in proPC4 75–90 ‐treated sperm. This result suggested that ADAM2 may be a natural substrate of sperm PCSK4 and its cleavage by the enzyme during acrosome reaction may be relevant to the fertilization process. J. Cell. Physiol. 226: 2817–2826, 2011. © 2011 Wiley‐Liss, Inc.