Cellular and Molecular Life Sciences

, Volume 66, Issue 17, pp 2913–2932 | Cite as

A small GTPase, human Rab32, is required for the formation of autophagic vacuoles under basal conditions

Research Article

Abstract

Here we show that a small GTPase, Rab32, is a novel protein required for the formation of autophagic vacuoles. We found that the wild-type or GTP-bound form of human Rab32 expressed in HeLa and COS cells is predominantly localized to the endoplasmic reticulum (ER), and overexpression induces the formation of autophagic vacuoles containing an autophagosome marker protein LC3, the ER-resident protein calnexin and endosomal/lysosomal membrane protein LAMP-2, even under nutrient-rich conditions. The recruitment of Rab32 to the ER membrane was necessary for autophagic vacuole formation, suggesting involvement of the ER as a source of autophagosome membranes. In contrast, the expression of the inactive form of, or siRNA-specific for, Rab32 caused the formation of p62/SQSTM1 and ubiquitinated protein-accumulating aggresome-like structures and significantly prevented constitutive autophagy. We postulate that Rab32 facilitates the formation of autophagic vacuoles whose membranes are derived from the ER and regulates the clearance of aggregated proteins by autophagy.

Keywords

Rab32 Autophagy Aggresome p62/SQSTM1 LC3 

Supplementary material

18_2009_80_MOESM1_ESM.doc (31 kb)
Supplementary material 1 (DOC 31 kb)
18_2009_80_MOESM2_ESM.pdf (12.1 mb)
Supplementary material 2 (PDF 12373 kb)

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Copyright information

© Birkhäuser Verlag, Basel/Switzerland 2009

Authors and Affiliations

  1. 1.Division of Pharmaceutical Cell Biology, Graduate School of Pharmaceutical SciencesKyushu UniversityFukuokaJapan

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