Combinatorial selective ER-phagy remodels the ER during neurogenesis

Area of Science:

• Cell Biology
• Neuroscience
• Molecular Biology

Background:

• The endoplasmic reticulum (ER) is vital for cellular functions, including protein synthesis and calcium homeostasis.
• ER remodelling is critical during neurogenesis, forming polarized neuronal structures like dendrites and axons.
• Previous research suggested autophagy's role in ER remodelling, with ER-phagy receptors like FAM134B linked to neuropathy, but mechanisms remain unclear.

Purpose of the Study:

• To quantitatively map ER proteome remodelling during selective autophagy.
• To understand the mechanisms of selective ER removal and the roles of individual ER-phagy receptors.
• To investigate ER remodelling during neuronal differentiation.

Main Methods:

• Utilized a genetically tractable induced neuron (iNeuron) system for in vitro differentiation and ER remodelling monitoring.
• Employed proteomic and computational tools to create a quantitative landscape of ER proteome remodelling.
• Analyzed single and combinatorial ER-phagy receptor mutants, using spatial sensors, flux reporters, and cryo-electron tomography.

Main Results:

• Delineated the contribution of each ER-phagy receptor to the magnitude and selectivity of ER protein clearance.
• Defined specific subsets of ER membrane and lumenal proteins as preferred clients for distinct receptors.
• Demonstrated receptor-specific autophagic capture of ER in axons and visualized ER membranes within neuronal autophagosomes.

Conclusions:

• Generated a molecular inventory of ER proteome remodelling via selective autophagy.
• Provided a versatile genetic toolkit for studying ER remodelling.
• Established a quantitative framework for understanding individual ER-phagy receptor contributions to ER reshaping during cell state transitions.