Moreover, when immunolabeling was carried out using scinderin antiserum #7, which was raised against native scinderin and did not cross-react with gelsolin, the scinderin distribution was identical to the one revealed by scinderin antiserum #6 labeling. For all those reasons, we believe that our immunolabeling accurately reflects scinderin presence and distribution in bovine tissues.
Scinderin may not be related exclusively to spermato-genic function. The finding of higher amounts of scinderin in fetal seminiferous tubules and of a cytoplasmic scinderin distribution that changed in a stage-specific manner in adult Sertoli cells suggests that spermatogenesis influences the quantity and localization of the protein in the testis. Moreover, the fluctuation of scinderin levels in spermatozoa following their transit through the epididymis suggests that the protein may participate in the maturation process by ensuring the appearance of sequential changes in the form/state of actin, which may be essential in the fertilizing capacity to the male gametes.
The nucleotide and amino acid sequence analysis revealed that scinderin possesses six domains, each containing three internal sequence motifs and two actin and two PIP2 binding sites, and showed 63% and 53% homology with gelsolin and villin, both being Ca2+-dependent F-actin-severing proteins. Gelsolin, a 90-kDa actin filament-capping and -severing protein that reportedly binds to the barbed ends of actin filament to prevent their growth and to sever the filaments, under Ca2+ and phospho-inositide control, was immunolocalized in capacitated spermatozoa under specific experimental conditions.