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PUTATIVE CREATINE KINASE M-ISOFORM IN HUMAN SPERM IS IDENTIFIED AS THE 70-KILODALTON HEAT SHOCK PROTEIN HSPA2
Citation:
Huszar, G., K. Stone, D J. Dix, AND L. Vigue. PUTATIVE CREATINE KINASE M-ISOFORM IN HUMAN SPERM IS IDENTIFIED AS THE 70-KILODALTON HEAT SHOCK PROTEIN HSPA2. BIOLOGY OF REPRODUCTION 63(3):925-932, (2000).
Description:
THE PUTATIVE CREATINE KINASE M-ISOFORM IN HUMAN SPERM
IS IDENTIFIED AS THE 70 kDa HEAT SHOCK PROTEIN HSPA2
* Gabor Huszar1, Kathryn Stone2, David Dix3 and Lynne Vigue1
1The Sperm Physiology Laboratory, Department of Obstetrics and Gynecology, 2 W.M. Keck Foundation Biotechnology Resource Laboratory, Yale University School of Medicine, New Haven, Connecticut 06510, and the 3Reproductive Toxicology Division, National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency, Research Triangle Park, North Carolina 27711.
ABSTRACT
We previously described a putative creatine kinase M-isoform in human sperm which is developmentally regulated and expressed during late spermiogenesis, simultaneously with cytoplasmic extrusion. We now identified this protein as the testis-expressed 70 kDa heat shock protein (HSP70) chaperone known as HspA2 (the human homologue of mouse Hsp70-2). We have isolated and characterized HspA2 (formerly CK-M) by amino acid sequencing and have localized it by immunocytochemistry to spermatids and in the tail of mature sperm. The specificity of the CK-M/HspA2 antiserum to HspA2 was demonstrated on immunoblots of 1- and 2-dimensional SDS-PAGE. In agreement with our earlier biochemical data, immunocytochemistry of testicular tissue indicated that the HspA2 is selectively expressed in mature spermatids and in sperm at the border of the adluminal compartment. The identity of HspA2 has been further confirmed by cross-absorption of the mouse HSP70-2 antibody by the HspA2/CK-M fraction, and by identical immunostaining patterns of human testicular tissue using either the anti-CK-M/HspA2 or an anti-mouse Hsp70-2 antisera. During spermiogenesis both cytoplasmic extrusion and plasma membrane remodeling, which facilitates the formation of the zona pellucida binding site, involve major intra-sperm protein transport which may be chaperoned by the HspA2. Accordingly, in immature human sperm, which fail to express HspA2, there is cytoplasmic retention and lack of zona pellucida binding. The present findings provide the biological rationale for the role of the HspA2/CK-M as an objective biochemical marker of sperm function and male fertility, which we have established in earlier clinical studies.
The information in this document has been funded wholly (or in part) by the U.S. Environmental Protection Agency. It has been subjected to review by the National Health and Environmental Effects Research Laboratory and approved for publication. Approval does not signify that the contents reflect the views of the Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.