Molecular Human Reproduction, Vol. 5, No. 6, 520-526,
June 1999
© 1999 European Society of Human Reproduction and Embryology
Calpain–calpastatin: a novel, complete calcium-dependent protease system in human spermatozoa
1 Department of Research, Worldwide Medical Corporation, Irvine, California 92618, 2 College of Medicine, University of California Irvine, Irvine, CA 92612, and 3 Department of Basic Sciences, Hitachi Chemical Research Center, Irvine, CA 92612, USA
Calpain, a calcium (Ca2+)-activated cysteine protease presents in several somatic mammalian cells, has been demonstrated to mediate specific Ca2+-dependent reactions including cell fusion. Because spermatozoa cells have an absolute Ca2+ requirement for penetration of oocytes, we have postulated that calpain would also be found in mammalian spermatozoa. Here we show that whole sperm homogenate and cell fractions prepared from ejaculated human spermatozoa contain calpain activity. Specific calpain inhibitors impaired this proteolytic activity. Unlike the enzyme described in somatic cells, sperm calpain was mostly particulate in nature and its activity was maximal at pH 9.0. Presence of sperm calpain was confirmed by immunoblot analysis using specific anti-calpain I and anti-calpain II antibodies. A 67 kDa calpain II protein and a 75 kDa calpain I protein were detected. Also spermatozoa contain the endogenous calpain inhibitor, calpastatin. We detected 158.8 ± 24.5 (mean ± SD) fmol calpastatin/mg sperm protein. Immunoblot analysis using specific antibodies showed a 68 kDa calpastatin protein located in the cytosolic fraction. This is the first demonstration that a complete calpain–calpastatin system exists in mammalian spermatozoa. Because calpain is a unique effector system for calcium-dependent processes, our data reveals a novel mechanism by which calcium exerts its regulatory functions in spermatozoa.
calpain/calpastatin/spermatozoa/calcium-dependent proteases/calcium regulation
4 To whom correspondence should be addresed at WMED, 199 Technology Drive, 150 Irvine, CA 92618, USA
CiteULike 
Connotea 
Del.icio.us What's this?
This article has been cited by other articles:
|
|
 |
|
  D. White, E. de Lamirande, and C. Gagnon Protein kinase C is an important signaling mediator associated with motility of intact sea urchin spermatozoa J. Exp. Biol., November 15, 2007; 210(22): 4053 - 4064. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 K Ashizawa, G J Wishart, S Katayama, D Takano, M Maeda, E Arakawa, and Y Tsuzuki Effects of calpain and Rho-kinase inhibitors on the acrosome reaction and motility of fowl spermatozoa in vitro Reproduction, January 1, 2006; 131(1): 71 - 79. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. Ben-Aharon, P. R Brown, N. Etkovitz, E. M Eddy, and R. Shalgi The expression of calpain 1 and calpain 2 in spermatogenic cells and spermatozoa of the mouse Reproduction, April 1, 2005; 129(4): 435 - 442. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Li and E. Goldberg A Novel N-Terminal Domain Directs Membrane Localization of Mouse Testis-Specific Calpastatin Biol Reprod, December 1, 2000; 63(6): 1594 - 1600. [Abstract] [Full Text]
|
|
|
|
|
|
S. Li, Z.-G. Liang, G.-Y. Wang, B. Yavetz, E. D. Kim, and E. Goldberg Molecular Cloning and Characterization of Functional Domains of a Human Testis-Specific Isoform of Calpastatin Biol Reprod, July 1, 2000; 63(1): 172 - 178. [Abstract] [Full Text]
|
|