Developmental Cell
Volume 20, Issue 1, 18 January 2011, Pages 131-139
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Short Article
Microautophagy of Cytosolic Proteins by Late Endosomes

https://doi.org/10.1016/j.devcel.2010.12.003Get rights and content
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Summary

Autophagy delivers cytosolic components to lysosomes for their degradation. The delivery of autophagic cargo to late endosomes for complete or partial degradation has also been described. In this report we present evidence that distinct autophagic mechanisms control cytosolic protein delivery to late endosomes and identify a microautophagy-like process that delivers soluble cytosolic proteins to the vesicles of late endosomes/multivesicular bodies (MVBs). This microautophagy-like process has selectivity and is distinct from chaperone-mediated autophagy that occurs in lysosomes. Endosomal microautophagy occurs during MVB formation, relying on the ESCRT I and III systems for formation of the vesicles in which the cytosolic cargo is internalized. Protein cargo selection is mediated by the chaperone hsc70 and requires the cationic domain of hsc70 for electrostatic interactions with the endosomal membrane. Therefore, we propose that endosomal microautophagy shares molecular components with both the endocytic and autophagic pathways.

Highlights

► Late endosomes take up cytosolic proteins through membrane invaginations ► Endosomal microautophagy (eMI) requires multivesicular body formation ► hsc70 mediates selective targeting of cytosolic proteins during eMI ► hsc70 binds to the endosomal membrane through its polybasic cluster

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