The prenylated Rab acceptor 1 (PRA1) superfamily member PRAF3 plays crucial roles in membrane traffic as a GDI displacement factor via protein interaction with a variety of Rab proteins, as well as in the modulation of antioxidant glutathione through its interaction with the amino acid transporter EAAC1.  It is known that the overexpression of PRAF3 induces the toxicity of the host cell, however, the factors capable of cancelling the cytotoxicity remained unknown.  Our findings demonstrate that Rab1a can protect from the cytotoxicity of PRAF3-overexpressed human cells.  Cytoprotective effects of Rab1a protein could further suggest that PRAF3 and Rab1a are closely related to each other physiologically and genetically.