MiT/TFE factors control ER-phagy via transcriptional regulation of FAM134B

ABSTRACT: Lysosomal degradation of the endoplasmic reticulum (ER) via autophagy (ER-phagy) is emerging as a critical regulator of ER homeostasis and function1. The selective incorporation of ER fragments into nascent autophagosomes is facilitated by ER resident proteins, ER-phagy receptors, that bind the autophagosomal LC3 protein via the cytosolic LC3 interacting domain (LIR) (REF). However, the molecular mechanisms that regulate ER-phagy in response to cellular needs are still largely unknown. We found that the MiT/TFE transcription factors - master regulators of lysosomal biogenesis and autophagy2- control ER-phagy by inducing the expression of the ER-phagy receptor FAM134B. This pathway is robustly activated in chondrocytes by FGF signaling, a critical regulator of chondrocyte differentiation3. FGF triggers TFEB/TFE3-mediated ER-phagy through JNK-dependent proteasomal degradation of the insulin receptor substrate 1 (IRS-1) protein and inhibition of the insulin signaling. FAM134B knock-down impairs cartilage growth and mineralization in medaka fish, suggesting a physiological role for this process during skeletal growth. Notably, we showed that the TFEB/TFE3-FAM134B axis promotes ER-phagy activation upon prolonged starvation. Thus, this study identifies MiT/TFE-factors as key transcriptional activators of ER-phagy in response to both metabolic and developmental cues.

INSTRUMENT(S):

ORGANISM(S): Rattus Norvegicus (rat)

TISSUE(S): Keratinocyte

SUBMITTER: Florian Bonn  

LAB HEAD: Carmine Settembre

PROVIDER: PXD015130 | Pride | 2020-07-15

REPOSITORIES: Pride