Open AccessHRES-1/Rab4 Promotes the Formation of LC3+ Autophagosomes and the Accumulation of Mitochondria during Autophagy
Author(s) -
Gergely Talabér,
Gabriella Miklóssy,
Zachary Oaks,
Yuxin Liu,
Sharon A. Tooze,
Dmitriy M. Chudakov,
Katalin Bánki,
András Perl
Publication year - 2014
Publication title -
plos one
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.99
H-Index - 332
ISSN - 1932-6203
DOI - 10.1371/journal.pone.0084392
Subject(s) - colocalization , autophagy , biology , mitochondrion , microbiology and biotechnology , tor signaling , biochemistry , signal transduction , apoptosis
HRES-1/Rab4 is a small GTPase that regulates endocytic recycling. It has been colocalized to mitochondria and the mechanistic target of rapamycin (mTOR), a suppressor of autophagy. Since the autophagosomal membrane component microtubule-associated protein light chain 3 (LC3) is derived from mitochondria, we investigated the impact of HRES-1/Rab4 on the formation of LC3 + autophagosomes, their colocalization with HRES-1/Rab4 and mitochondria, and the retention of mitochondria during autophagy induced by starvation and rapamycin. HRES-1/Rab4 exhibited minimal baseline colocalization with LC3, which was enhanced 22-fold upon starvation or 6-fold upon rapamycin treatment. Colocalization of HRES-1/Rab4 with mitochondria was increased >2-fold by starvation or rapamycin. HRES-1/Rab4 overexpression promoted the colocalization of mitochondria with LC3 upon starvation or rapamycin treatment. A dominant-negative mutant, HRES-1/Rab4 S27N had reduced colocalization with LC3 and mitochondria upon starvation but not rapamycin treatment. A constitutively active mutant, HRES-1/Rab4 Q72L showed diminished colocalization with LC3 but promoted the partitioning of mitochondria with LC3 upon starvation or rapamycin treatment. Phosphorylation-resistant mutant HRES-1/Rab4 S204Q showed diminished colocalization with LC3 but increased partitioning to mitochondria. A newly discovered C-terminally truncated native isoform, HRES-1/Rab4 1–121 , showed enhanced localization to LC3 and mitochondria without starvation or rapamycin treatment. HRES-1/Rab4 1–121 increased the formation of LC3 + autophagosomes in resting cells, while other isoforms promoted autophagosome formation upon starvation. HRES-1/Rab4, HRES-1/Rab4 1–121 , HRES-1/Rab4 Q72L and HRES-1/Rab4 S204Q promoted the accumulation of mitochondria during starvation. The specificity of HRES-1/Rab4-mediated mitochondrial accumulation is indicated by its abrogation by dominant-negative HRES-1/Rab4 S27N mutation. The formation of interconnected mitochondrial tubular networks was markedly enhanced by HRES-1/Rab4 Q72L upon starvation, which may contribute to the retention of mitochondria during autophagy. The present study thus indicates that HRES-1/Rab4 regulates autophagy through promoting the formation of LC3 + autophagosomes and the preservation of mitochondria.