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Prolyl Endopeptidase (PREP) is Involved in the Reproductive Functions and Cytoskeletal Organization in Rat Spermatogenesis and in Mammalian Sperm

Prolyl endopeptidase (PREP) is an enzyme which cleaves several peptide hormones and neuropeptides at the carboxyl side of proline residues, involved in many biological processes, including cell proliferation and differentiation, glucose metabolism, learning, memory and cognitive disorders. Moreover, PREP was identified as binding partner of tubulin, suggesting that this endopeptidase may be involved in microtubule-associate processes, independent of its peptidase activity. Several reports have also suggested PREP participation in both male and female reproduction-associated processes. In this work, we assessed the possible association of PREP with the morphogenesis of rat testis, profiling its localization versus tubulin, during the first wave of spermatogenesis and in the adult gonad (from 7 to 60 dpp). Here we show that, in mitotic phases, PREP shares its localization with tubulin in Sertoli cells, gonocytes and spermatogonia. Later, during meiosis, both proteins are found in spermatocytes, and in the cytoplasm of Sertoli cells protrusions, which surround the germ cells, while, during spermiogenesis, they both localize in the cytoplasm of round and elongating spermatids. Finally, they are expressed in the flagellum of mature gametes, as corroborated by additional immunolocalization analysis on both rat and human sperm. Our data strongly support the hypothesis of a role of PREP in supporting a correct reproductive function and in cytoskeletal organization during Mammalian testis morphogenesis and gamete progression, while also hinting at its possible investigation as a morphological marker of germ cell and sperm physiology. Summary statement In this paper we show the co-localization of the enzyme PREP with tubulin during the first wave of rat spermatogenesis and in mature gametes of rat and human.