An endolysosome membrane transformation process for engulfment of autophagosomes independently of ESCRT

Abstract

Endolysosome, usually regarded as the cellular recycling bin, digests materials from multiple origins. The materials from different origins are delivered to endolysosome through the vesicle fusion, kiss-and-run mechanisms, CMA or microautophagy. However, it remains unknown whether endolysosome can receive cargo via other ways. Here, we reported another endolysosomal process for receiving materials. In this, endolysosome receives materials by extending two arms which embraces autophagosomes and engulfs the autophagosomes ultimately, but not via the conventional fusion of autophagosomes with endolysosomes. We named this process as LEA (lysosome eats autophagosome) and the endolysosome arms as LF (endolysosome filopodia) provisionally. The endolysosomes with engulfed autophagosomes (LEA endolysosomes) get more autophagosomes via the fusion with other LEA endolysosomes. The engulfed autophagosomes are labelled by F-actin on their membranes and have ER protein Sec61{beta} and peroxisome protein Pex14 inside their lumens, but mitochondria are excluded outside endolysosome. Our discovery of LEA and LF reveal an unidentified endolysosome transformation process which is responsible for receiving cargoes.