RAB24 facilitates clearance of autophagic compartments during basal conditions

RAB24 belongs to a family of membrane traffic controlling RAB proteins and has been implicated to function in autophagy. Here we confirm the intracellular localization of RAB24 to autophagic vacuoles with immuno electron microscopy and cell fractionation, and show that prenylation and guanine nucleotide binding are necessary for the targeting of RAB24 to autophagic compartments. Further, we show that RAB24 plays a role in the maturation and/or clearance of autophagic compartments under nutrient-rich conditions, but not during short amino acid starvation. Quantitative electron microscopy showed an increase in the numbers of late autophagic compartments in cells silenced for RAB24, and mRFP-GFP-LC3 probe and autophagy flux experiments indicated that this was due to a hindrance in their clearance. Formation of autophagosomes was shown to be unaffected by RAB24 silencing with siRNA. A defect in aggregate clearance in the absence of RAB24 was also shown in cells forming polyglutamine aggregates. This study places RAB24 function in the termination of the autophagic process under nutrient-rich conditions.Peer reviewe