RAB24 facilitates clearance of autophagic compartments during basal conditions.
RAB24 belongs to a family of small GTPases 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 shows an increase in the numbers of late autophagic compartments in cells silenced for RAB24, and mRFP-GFP-LC3 probe and autophagy flux experiments indicate that this is due to a hindrance in their clearance. Formation of autophagosomes is shown to be unaffected by RAB24-silencing with siRNA. A defect in aggregate clearance in the absence of RAB24 is also shown in cells forming polyglutamine aggregates. This study places RAB24 function in the termination of the autophagic process under nutrient-rich conditions.
a Department of Biosciences, Division of Biochemistry and Biotechnology; University of Helsinki ; Helsinki , Finland.
Päivi
P
Ylä-Anttila
a Department of Biosciences, Division of Biochemistry and Biotechnology; University of Helsinki ; Helsinki , Finland.
Elisa
E
Mikkonen
a Department of Biosciences, Division of Biochemistry and Biotechnology; University of Helsinki ; Helsinki , Finland.
Kaisa E
KE
Happonen
b Department of Biochemistry, Institute of Basic Medical Sciences; University of Oslo ; Oslo , Norway.
Petter
P
Holland
c Laboratory of Proteomics and Biomolecular Science; Research Support Center; Juntendo University Graduate School of Medicine ; Tokyo , Japan.
Takashi
T
Ueno
b Department of Biochemistry, Institute of Basic Medical Sciences; University of Oslo ; Oslo , Norway.
Anne
A
Simonsen
a Department of Biosciences, Division of Biochemistry and Biotechnology; University of Helsinki ; Helsinki , Finland.
Eeva-Liisa
EL
Eskelinen
D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D001343:Autophagy / Q000502:physiology*; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D010588:Phagosomes / Q000378:metabolism*; D034741:RNA, Small Interfering / Q000378:metabolism; D013217:Starvation / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
D000596:Amino Acids; D008869:Microtubule-Associated Proteins; D034741:RNA, Small Interfering; C086224:Rab24 protein, mouse; D020691:rab GTP-Binding Proteins
RAB24; aggregate; autophagosome; autophagy; basal; membrane; starvation