Fig 1: RAB3GAP1 and WDR44 are FFAT-like interactors of VAPB. (A) Flag-VAPB immunoprecipitated from HeLa cells interacts with RAB3GAP1, RAB3GAP2 and WDR44. The RAB3GAP1 and WDR44 interactions with VAPB are mediated by FFAT motifs. VAPB immunoprecipitation from mouse brain extract confirms its interaction with RAB3GAP1 (B), ASNA1 and WDR44 (C). Flag-RAB3GAP1 WT and F585A/F586A (FF-AA) (D) and Flag-WDR44 WT and Δ1-15 (E) were immunoprecipitated from U2OS cells. Both RAB3GAP1 and WDR44 contain FFAT motifs, as indicated in the top panels, which are responsible for the interaction with VAPB. The formation of the RAB3GAP1/2 heterodimer is not affected by the mutation of the FFAT motif in RAB3GAP1. (F) Immunoprecipitation of Flag-VAPA WT, Flag-VAPB WT or the K87D M89D mutant of VAPB from U2OS cells shows that the KM-DD mutant is defective in interacting with RAB3GAP1 and WDR44. FF-AA, F585A/F586A; IP, immunoprecipitate.