Prolyl endopeptidase (PREP) is a post-proline cleaving enzyme. It is involved in the regulation of multiple inositol polyphosphate phosphatase activity implicated in the pathway of inositol 1,4,5-trisphosphate, resulting in the modulation of cytosolic Ca2+ levels. Besides its peptidase activity, PREP was identified as a binding partner of tubulin, suggesting that it may participate in microtubule-associate processes. In this paper, we evaluated the expression of PREP mRNA and protein by polymerase chain reaction and western blot analyses and its co-localization with tubulin by immunofluorescence in adult mouse seminal vesicles. We showed that both proteins are cytoplasmic: tubulin is localized at the apical half part of the cell, while PREP has a more diffuse localization, showing a prominent distribution at the apical cytoplasm. These findings support our hypothesis of a specific role for PREP in cytoskeletal rearrangement that occurs during the exocytosis of secretory vesicles, and in particular its association with tubulin filaments. Moreover, it may regulate Ca2+ levels, and promote the final step of vesicular exocytosis, namely the fusion of the vesicles with the plasma membrane. These results strongly suggest that there is a pivotal role for PREP in vesicle exocytosis, as well as in the physiology of mouse seminal vesicles.

Specimens belonging to 20 species (7 families) of catfishes have been collected in French Guyana. The anatomy and histology of the male reproductive tracts have been studied. In the most primitivespecies (Helogeneidae, Ariidae) no seminal vesicle is present in the males. In the Pimelodidae,Loricariidae and Callichthyidae (and also in an african Bagridae), there is a progressive transition, going from anterior to posterior in the male tract, from testicular tissue towards round germ cell-free tubules and finally to seminal vesicular tissue. All these families produce round-headed spermatozoa and have external fertilization. The Auchenipteridae and Ageneiosidae are characterized by elongated sperm nuclei, internal fertilization with the aid of a gonopodium and sperm storage in the ovaries. In the Auchenipteridae there is a clear-cut distinction between testes and seminal vesicles. In the Ageneiosidae there is no seminal vesicle, but the dilated deferent duct displays a high secretory activity. Depending on the family and species, the seminal vesicles may carry out either one or both of the two main functions: secretion and sperm storage. In addition, in some species, sperm is also stored in one or two accessory pouches until fertilization. The trends that we have observed in the changes in the organization of the reproductive tracts are in agreement with the hypotheses proposed for catfish evolution from comparative anatomical data.