mUBPy is a novel centrosome-associated protein and interacts with γ-tubulin

mUBPy is a deubiquitinating enzyme expressed preferentially in male germ cells and neurons. Recently, mUBPy has been shown to be involved in the down-regulation of growth factor receptors. In mouse spermatozoa mUBPy interacts with the sperm-specific molecular chaperone MSJ-1 and associates with the proteasome. The ubiquitin/proteasome system plays a key role during spermatogenesis to yield functional spermatozoa. Immunoelectron microscopy has been here used to localize both mUBPy and MSJ-1 in mouse spermatozoa. mUBPy and MSJ-1 label the cytoplasmic side of the acrosomal membrane and the centrosome, two sperm structures fundamental for a successful fertilization. In vitro protein interaction assay reveals that mUBPy is able to bind gamma-tubulin, a centrosomal protein marker. This protein interaction has been confirmed in vivo by double protein immunolabelling in spermatogenic cells. Upon the grounds of these findings and in the light of recent acquisition on the centrosome biology, we suggest that mUBPy could have a key role during mouse fertilization and propose mUBPy as a novel centrosomal component.