An initial step of GAS-containing autophagosome-like vacuoles formation requires Rab7.
Group A streptococcus (GAS; Streptococcus pyogenes) is a common pathogen that invades non-phagocytic human cells via endocytosis. Once taken up by cells, it escapes from the endocytic pathway to the cytoplasm, but here it is contained within a membrane-bound structure termed GAS-containing autophagosome-like vacuoles (GcAVs). The autophagosome marker GFP-LC3 associates with GcAVs, and other components of the autophagosomal pathway are involved in GcAV formation. However, the mechanistic relationship between GcAV and canonical autophagy is largely unknown. Here, we morphologically analyzed GcAV formation in detail. Initially, a small, GFP-LC3-positive GcAV sequesters each streptococcal chain, and these then coalesce into a single, large GcAV. Expression of a dominant-negative form of Rab7 or RNAi-mediated knockdown of Rab7 prevented the initial formation of small GcAV structures. Our results demonstrate that mechanisms of GcAV formation includes not only the common machinery of autophagy, but also Rab7 as an additional component, which is dispensable in canonical autophagosome formation.
Yamaguchi
Hitomi
H
Structural Biology Center, National Institute of Genetics/SOKENDAI, Mishima-Shizuoka, Japan.
Nakagawa
Ichiro
I
Yamamoto
Akitsugu
A
Amano
Atsuo
A
Noda
Takeshi
T
Yoshimori
Tamotsu
T
D001343:Autophagy; D006367:HeLa Cells; D006801:Humans; D008869:Microtubule-Associated Proteins; D013297:Streptococcus pyogenes; D014617:Vacuoles / Q000378:metabolism / Q000821:virology*; D020691:rab GTP-Binding Proteins / Q000502:physiology*; D000090802:rab7 GTP-Binding Proteins
C477012:MAP1LC3A protein, human; D008869:Microtubule-Associated Proteins; D000090802:rab7 GTP-Binding Proteins; C000716463:rab7 GTP-binding proteins, human; D020691:rab GTP-Binding Proteins