PtdIns4P exchange at endoplasmic reticulum-autolysosome contacts is essential for autophagy and neuronal homeostasis

ABSTRACT

Inter-organelle contacts enable crosstalk among organelles, facilitating the exchange of materials and coordination of cellular events. In this study, we demonstrated that, upon starvation, autolysosomes recruit Pi4KIIα (Phosphatidylinositol 4-kinase II α) to generate phosphatidylinositol−4-phosphate (PtdIns4P) on their surface and establish endoplasmic reticulum (ER)-autolysosome contacts through PtdIns4P binding proteins Osbp (Oxysterol binding protein) and cert (ceramide transfer protein). We found that the Sac1 (Sac1 phosphatase), Osbp, and cert proteins are required for the reduction of PtdIns4P on autolysosomes. Loss of any of these proteins leads to defective macroautophagy/autophagy and neurodegeneration. Osbp, cert, and Sac1 are required for ER-Golgi contacts in fed cells. Our data establishes a new mode of organelle contact formation – the ER-Golgi contact machinery can be reused by ER-autolysosome contacts by re-locating PtdIns4P from the Golgi apparatus to autolysosomes when faced with starvation.

Abbreviations: Atg1: Autophagy-related 1; Atg8: Autophagy-related 8; Atg9: Autophagy-related 9; Atg12: Autophagy-related 12; cert: ceramide transfer protein; Cp1/CathL: cysteine proteinase−1; CTL: control; ER: endoplasmic reticulum; ERMCS: ER-mitochondria contact site; fwd: four wheel drive; GM130: Golgi matrix protein 130 kD; Osbp: Oxysterol binding protein; PG: phagophore; PtdIns4K: phosphatidylinositol 4-kinase; Pi4KIIα: Phosphatidylinositol 4-kinase II α; Pi4KIIIα: Phosphatidylinositol 4-kinase III α; PtdIns4P: phosphatidylinositol−4-phosphate; PR: photoreceptor cell; RT: room temperature; Sac1: Sac1 phosphatase; Stv: starvation; Syx17: Syntaxin 17; TEM: transmission electron microscopy; VAP: VAMP-associated protein.

KEYWORDS:

• Drosophila
• endoplasmic reticulum-autolysosome contacts
• Golgi apparatus
• PtdIns4P
• autophagy

Acknowledgements

We are grateful to THFC, BDSC, DGRC, and core facility in LSI, Zhejiang University for providing fly strains, cDNA clones, and technique supports.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

All data generated in this study have been included in the main text or supplementary materials.

Supplementary Material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/15548627.2023.2222556.

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

Dr. Tong Chao is supported by National Natural Science Foundation of China (92254305, 92157201, 32030027, 91754103), Fundamental research funds for the central universities, and Shenzhen Bay Scholars Program. Dr. Liu Hao is supported by National Natural Science Foundation of China (32100599).