Expression profile of PRAF2 in the human brain and enrichment in synaptic vesicles.

PRA1 domain family, member 2 (PRAF2) is a novel 19-kDa protein with a prenylated Rab acceptor 1 (PRA1) motif and four transmembrane domains. Our previous studies revealed that PRAF2 is highly expressed in the brain and serves as a candidate prognostic marker in neuroblastoma (NB). PRAF2 is related to proteins PRAF1 (PRA1, prenylin, Yip3) and PRAF3 (GTRAP3-18, JWA, Arl6-IP5), both of which are enriched in the brain and implicated in cellular transport and endo/exocytic vesicle trafficking. However, the function for PRAF2 remains unknown. In this study, we analyzed the distribution and localization of PRAF2 in the mature human brain using two new antibodies specific for the protein. Analysis by immunohistochemistry revealed that in the human cerebellum, the PRAF2 protein was strongly expressed in Purkinje cells and, more moderately, in cells of the molecular and the granular layers. In the cerebral cortex, hippocampus, and lateral ventricles, PRAF2 protein was detected in neuronal cells, but not in non-neuronal cells. Intriguingly, immunoblot analysis revealed that PRAF2 is enriched in synaptic vesicles (SVs) prepared from rat brains. The expression of PRAF2 in specific regions of the brain including SVs suggest an important physiological function for this novel protein, possibly by participating in multiple aspects of SV maturation, transport, and signal transmission.