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