p62/SQSTM1 Binds Directly to Atg8/LC3 to Facilitate Degradation of Ubiquitinated Protein Aggregates by Autophagy

Abstract

Protein degradation by basal constitutive autophagy is important to avoid accumulation of polyubiquitinated protein aggregates and development of neurodegenerative diseases. The polyubiquitin-binding protein p62/SQSTM1 is degraded by autophagy. It is found in cellular inclusion bodies together with polyubiquitinated proteins and in cytosolic protein aggregates that accumulate in various chronic, toxic, and degenerative diseases. Here we show for the first time a direct interaction between p62 and the autophagic effector proteins LC3A and -B and the related ␥-aminobutyrate receptor-associated protein and ␥-aminobutyrate receptor-associated-like proteins. The binding is mediated by a 22-residue sequence of p62 containing an evolutionarily conserved motif. To monitor the autophagic sequestration of p62-and LC3-positive bodies, we developed a novel pH-sensitive fluorescent tag consisting of a tandem fusion of the red, acid-insensitive mCherry and the acid-sensitive green fluorescent proteins. This approach revealed that p62-and LC3-positive bodies are degraded in autolysosomes. Strikingly, even rather large p62-positive inclusion bodies (2 m diameter) become degraded by autophagy. The specific interaction between p62 and LC3, requiring the motif we have mapped, is instrumental in mediating autophagic degradation of the p62-positive bodies. We also demonstrate that the previously reported aggresome-like induced structures containing ubiquitinated proteins in cytosolic bodies are dependent on p62 for their formation. In fact, p62 bodies and these structures are indistinguishable. Taken together, our results clearly suggest that p62 is required both for the formation and the degradation of polyubiquitin-containing bodies by autophagy.

Melatonin activates Parkin translocation and rescues the impaired mitophagy activity of diabetic cardiomyopathy through Mst1 inhibition

“…These results indicate that melatonin up‐regulates Parkin‐mediated mitophagy, thus eliminating dysfunctional mitochondrial and maintaining the homoeostasis of mitochondria in the diabetic heart. The linkage of the ubiquitin‐binding protein p62 to ubiquitin on the mitochondrion and lipidated LC3II on the autophagosome provides a physical attachment point for mitophagy 13, 22, 59. The present study also indicates that mitochondrial p62 increases after melatonin administration.…”

Structural basis of FYCO1 and MAP1LC3A interaction reveals a novel binding mode for Atg8-family proteins

“…17,26 Additional acidic residues and/or serine/threonine phosphorylation sites preceding the hydrophobic LIR core sequence are also commonly found in LIR-containing proteins, and are demonstrated to regulate their specific interactions with Atg8-family members. 20,[30][31][32] Recently, a noncanonical LIR motif, which solely comprises 3 consecutive hydrophobic residues (LVV), has been found in the autophagy receptor CALCOCO2/NDP52. 33 This atypical LIR motif (termed as CLIR) exclusively interacts with the Atg8-family member, LC3C, and endows CALCOCO2 with a unique function in xenophagy.…”

“…Accumulating evidence showed that the specific interactions between Atg8-binding proteins and Atg8-family proteins were mainly mediated by a short motif named LC3-interacting region (LIR). [20][21][22][23][24][25][26][27][28][29] The canonical LIR motif has the consensus core sequence QxxG where Q being aromatic residues (W/F/Y), and G being bulk hydrophobic residues (L/I/ V). 17,26 Additional acidic residues and/or serine/threonine phosphorylation sites preceding the hydrophobic LIR core sequence are also commonly found in LIR-containing proteins, and are demonstrated to regulate their specific interactions with Atg8-family members.…”

Acute exposure to organic and inorganic sources of copper: Differential response in intestinal cell lines

“…SRXN1 is a redox‐activated thiol switch important in the reversal of glutathionylation reactions (Findlay et al., 2006), while AKR1B1 is involved in lipid peroxidation detoxification (Barski, Tipparaju, & Bhatnagar, 2008). SQSTM1 and PICALM have both been implicated in autophagy (Moreau et al., 2014; Pankiv et al., 2007). However, given the small differences between the organic copper compounds and CuSO 4 and the very variable response with the inorganic copper product, these may not be suitable markers to monitor organic copper overload.…”