Mammalian autophagosomes form from finger-like phagophores

Claudia Puri; Matthew J Gratian; David C Rubinsztein

doi:10.1016/j.devcel.2023.08.016

Mammalian autophagosomes form from finger-like phagophores

Dev Cell. 2023 Dec 4;58(23):2746-2760.e5. doi: 10.1016/j.devcel.2023.08.016. Epub 2023 Sep 7.

Authors

Claudia Puri¹, Matthew J Gratian², David C Rubinsztein³

Affiliations

¹ Department of Medical Genetics, University of Cambridge, Cambridge, UK; Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK; UK Dementia Research Institute, Cambridge Biomedical Campus, University of Cambridge, The Keith Peters Building Cambridge, Hills Road, Cambridge CB2 0XY, UK.
² Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK.
³ Department of Medical Genetics, University of Cambridge, Cambridge, UK; Cambridge Institute for Medical Research, University of Cambridge, Cambridge, UK; UK Dementia Research Institute, Cambridge Biomedical Campus, University of Cambridge, The Keith Peters Building Cambridge, Hills Road, Cambridge CB2 0XY, UK. Electronic address: dcr1000@cam.ac.uk.

PMID: 37683632
DOI: 10.1016/j.devcel.2023.08.016

Abstract

The sequence of morphological intermediates that leads to mammalian autophagosome formation and closure is a crucial yet poorly understood issue. Previous studies have shown that yeast autophagosomes evolve from cup-shaped phagophores with only one closure point, and mammalian studies have inferred that mammalian phagophores also have single openings. Our superresolution microscopy studies in different human cell lines in conditions of basal and nutrient-deprivation-induced autophagy identified autophagosome precursors with multifocal origins that evolved into unexpected finger-like phagophores with multiple openings before becoming more spherical structures. Compatible phagophore structures were observed with whole-mount and conventional electron microscopy. This sequence of events was visualized using advanced SIM² superresolution live microscopy. The finger-shaped phagophore apertures remained open when ESCRT function was compromised. The efficient closure of autophagic structures is important for their release from the recycling endosome. This has important implications for understanding how autophagosomes form and capture various cargoes.

Keywords: CHMP2A; ESCRT complex; RAB11A; VPS4A; autophagosome; autophagy; mitophagy; phagophore; recycling endosome; superresolution microscopy.

MeSH terms

Animals
Autophagosomes*
Autophagy*
Cell Line
Endosomes / metabolism
Humans
Mammals
Phagocytosis