Calcium-dependent actin filament-severing protein scinderin levels and localization in bovine testis, epididymis, and spermatozoa

We assessed the levels and localization of the actin filament-severing prot ein scinderin, in fetal and adult bovine testes, and in spermatozoa during and following the epididymal transit. We performed immunoblots on seminifer ous tubules and interstitial cells isolated by enzymatic digestion, and on bovine chromaffin cells, spermatozoa, aorta, and vena cava. Immunoperoxidas e labeling was done on Bouin's perfusion-fixed testes and epididymis tissue sections, and on spermatozoa. In addition, immunofluorescence labeling was done on spermatozoa. Immunoblots showed one 80-kDa band in chromaffin cell s, fetal and adult tubules, interstitial cells, spermatozoa, aorta, and ven a cava. Scinderin levels were higher in fetal than in adult seminiferous tu bules but showed no difference between fetal and adult interstitial cells. Scinderin levels were higher in epididymal than in ejaculated spermatozoa. Scinderin was detected in a region corresponding with the subacrosomal spac e in the round spermatids and with the acrosome in the elongated spermatids . In epididymal spermatozoa, scinderin was localized to the anterior acroso me and the equatorial segment, but in ejaculated spermatozoa, the protein a ppeared in the acrosome and the post-equatorial segment of the head. In Ser toli cells, scinderin was detected near the cell surface and within the cyt oplasm, where it accumulated near the base in a stage-specific manner. In t he epididymis, scinderin was localized next to the surface of the cells; in the tail, it collected near the base of the principal cells. In Sertoli ce lls and epididymal cells, scinderin may contribute to the regulation of tig ht junctional permeability and to the release of the elongated spermatids b y controlling the state of perijunctional actin. In germ cells, scinderin m ay assist in the shaping of the developing acrosome and influence the ferti lity of the spermatozoa.