SQSTM1, lipid droplets and current state of their lipophagy affairs. 2023

Ankit Shroff, and Taras Y Nazarko
Department of Biology, Georgia State University, Atlanta, GA, USA.

SQSTM1/p62 (sequestosome 1) is a well-established indicator of macroautophagic/autophagic flux. It was initially characterized as the ubiquitin-binding autophagic receptor in aggrephagy, the selective autophagy of ubiquitinated protein aggregates. Recently, several studies correlated its levels with the abundance of intracellular lipid droplets (LDs). In the absence of a bona fide receptor for the selective autophagy of LDs (lipophagy), a few studies demonstrated the role of SQSTM1 in lipophagy. Our analysis of these studies shows that SQSTM1 colocalizes with LDs, bridges them with phagophores, is co-degraded with them in the lysosomes, and affects LD abundance in a variety of cells and under diverse experimental conditions. Although only one study reported all these functions together, the overwhelming and complementary evidence from other studies suggests that the role of SQSTM1 in lipophagy via tagging, movement, aggregation/clustering and sequestration of LDs is rather a common phenomenon in mammalian cells. As ubiquitination of the LD-associated proteins under stress conditions is increasingly recognized as another common phenomenon, some other ubiquitin-binding autophagic receptors, such as NBR1 and OPTN, might soon join SQSTM1 on a list of the non-exclusive lipophagy receptors.Abbreviations: LD: lipid droplet; LIR: LC3-interacting region; PAT: Perilipin, ADRP and TIP47 domain; SAR: selective autophagy receptor.

UI MeSH Term Description Entries
D008322 Mammals Warm-blooded vertebrate animals belonging to the class Mammalia, including all that possess hair and suckle their young. Mammalia,Mammal
D011506 Proteins Linear POLYPEPTIDES that are synthesized on RIBOSOMES and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of AMINO ACIDS determines the shape the polypeptide will take, during PROTEIN FOLDING, and the function of the protein. Gene Products, Protein,Gene Proteins,Protein,Protein Gene Products,Proteins, Gene
D002352 Carrier Proteins Proteins that bind or transport specific substances in the blood, within the cell, or across cell membranes. Binding Proteins,Carrier Protein,Transport Protein,Transport Proteins,Binding Protein,Protein, Carrier,Proteins, Carrier
D000071456 Sequestosome-1 Protein A multidomain protein that is highly conserved among multicellular organisms. It contains a ZZ-type ZINC FINGER domain, C-terminal UBIQUITIN - associated (UBA) domain, and interacts with many other signaling proteins and enzymes including, atypical PROTEIN KINASE C; TNF RECEPTOR-ASSOCIATED FACTOR 6; subunits of the mTORC1 complex, and CASPASE-8. It functions in AUTOPHAGY as a receptor for the degradation of ubiquitinated substrates, and to co-ordinate signaling in response to OXIDATIVE STRESS. EBI3-Associated Protein of 60 KDa,EBIAP Protein,Phosphotyrosine-Independent Ligand For The Lck SH2 Domain Of 62 Kda,Ubiquitin-Binding Protein p62,EBI3 Associated Protein of 60 KDa,Phosphotyrosine Independent Ligand For The Lck SH2 Domain Of 62 Kda,Sequestosome 1 Protein,Ubiquitin Binding Protein p62
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D001343 Autophagy The segregation and degradation of various cytoplasmic constituents via engulfment by MULTIVESICULAR BODIES; VACUOLES; or AUTOPHAGOSOMES and their digestion by LYSOSOMES. It plays an important role in BIOLOGICAL METAMORPHOSIS and in the removal of bone by OSTEOCLASTS. Defective autophagy is associated with various diseases, including NEURODEGENERATIVE DISEASES and cancer. Autophagocytosis,ER-Phagy,Lipophagy,Nucleophagy,Reticulophagy,Ribophagy,Autophagy, Cellular,Cellular Autophagy,ER Phagy
D025801 Ubiquitin A highly conserved 76-amino acid peptide universally found in eukaryotic cells that functions as a marker for intracellular PROTEIN TRANSPORT and degradation. Ubiquitin becomes activated through a series of complicated steps and forms an isopeptide bond to lysine residues of specific proteins within the cell. These "ubiquitinated" proteins can be recognized and degraded by proteosomes or be transported to specific compartments within the cell. APF-1,ATP-Dependent Proteolysis Factor 1,HMG-20,High Mobility Protein 20,Ubiquitin, Human,ATP Dependent Proteolysis Factor 1,Human Ubiquitin
D066292 Lipid Droplets Dynamic cytoplasmic organelles found in almost all cells. They consist of a central core of LIPIDS surrounded by a phospholipid monolayer studded with surface proteins, and are involved in LIPID METABOLISM and storage. Adiposomes,Lipid Bodies,Lipid Storage Bodies,Oil Bodies,Oleosomes,Spherosomes,Adiposome,Droplet, Lipid,Droplets, Lipid,Lipid Body,Lipid Droplet,Lipid Storage Body,Oil Body,Oleosome,Spherosome,Storage Bodies, Lipid,Storage Body, Lipid

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