An Importin protein that mediates growth factor signalling and pathway crosstalk: Its roles in spermatogenesis

Signalling through many distinct pathways drive normal testis development and are essential for normal fertility in males. We are investigating an importin protein, IPO5 (also named importin 5) ,a nucleocytoplasmic transport factor which selectively binds and carries cytoplasmic cargo proteins into the nucleus. In this manner, its actions can control signaling by Transforming Growth Factor-beta superfamily proteins (for example, Bone Morphogenetic Proteins {BMPs} and activins) as well as Wnts. Our published work has demonstrated that IPO5 synthesis is highly regulated during spermatogenesis, both in fetal life and in adulthood, and we have an ongoing research effort to identify what its cargo and functions are during spermatogenesis. We have new evidence that IPO5 also serves as a protein scaffold, to anchor proteins in subcellular regions, including in developing sperm. Goals of this project are to validate potential binding partners we have already identified at different stages of spermatogenesis, though cell culture and knockdown experiments, primarily working with cell lines, but also through interrogation of samples collected from our unique strains of IPO5 KO mice. Knockdown of IPO5 or its cargo in cell lines using siRNA may be performed in conjunction with addition of signalling pathways inhibitors; analyses we generally conduct include measurements of pathway activity using direct reporters of transcriptional activation (eg. luciferase activity), analysis of downstream target gene activity, and evaluation of cell functions (migration, adhesion, proliferation, survival, differentiation).