Role of autophagy, SQSTM1, SH3GLB1, and TRIM63 in the turnover of nicotinic acetylcholine receptors.
Removal of ubiquitinated targets by autophagosomes can be mediated by receptor molecules, like SQSTM1, in a mechanism referred to as selective autophagy. While cytoplasmic protein aggregates, mitochondria, and bacteria are the best-known targets of selective autophagy, their role in the turnover of membrane receptors is scarce. We here showed that fasting-induced wasting of skeletal muscle involves remodeling of the neuromuscular junction (NMJ) by increasing the turnover of muscle-type CHRN (cholinergic receptor, nicotinic/nicotinic acetylcholine receptor) in a TRIM63-dependent manner. Notably, this process implied enhanced production of endo/lysosomal carriers of CHRN, which also contained the membrane remodeler SH3GLB1, the E3 ubiquitin ligase, TRIM63, and the selective autophagy receptor SQSTM1. Furthermore, these vesicles were surrounded by the autophagic marker MAP1LC3A in an ATG7-dependent fashion, and some of them were also positive for the lysosomal marker, LAMP1. While the amount of vesicles containing endocytosed CHRN strongly augmented in the absence of ATG7 as well as upon denervation as a model for long-term atrophy, denervation-induced increase in autophagic CHRN vesicles was completely blunted in the absence of TRIM63. On a similar note, in trim63(-/-) mice denervation-induced upregulation of SQSTM1 and LC3-II was abolished and endogenous SQSTM1 did not colocalize with CHRN vesicles as it did in the wild type. SQSTM1 and LC3-II coprecipitated with surface-labeled/endocytosed CHRN and SQSTM1 overexpression significantly induced CHRN vesicle formation. Taken together, our data suggested that selective autophagy regulates the basal and atrophy-induced turnover of the pentameric transmembrane protein, CHRN, and that TRIM63, together with SH3GLB1 and SQSTM1 regulate this process.
Institute of Toxicology and Genetics; Karlsruhe Institute of Technology; Eggenstein-Leopoldshafen, Germany.
Muzamil Majid
MM
Khan
Institute of Toxicology and Genetics; Karlsruhe Institute of Technology; Eggenstein-Leopoldshafen, Germany.
Siegfried
S
Strack
Institute of Toxicology and Genetics; Karlsruhe Institute of Technology; Eggenstein-Leopoldshafen, Germany.
Franziska
F
Wild
Department of Integrative Pathophysiology; Universitätsmedizin Mannheim; Mannheim, Germany.
Akira
A
Hanashima
Department of Integrative Pathophysiology; Universitätsmedizin Mannheim; Mannheim, Germany.
Alexander
A
Gasch
Department of Integrative Pathophysiology; Universitätsmedizin Mannheim; Mannheim, Germany.
Kathrin
K
Brohm
Institute of Applied Informatics; Karlsruhe Institute of Technology; Eggenstein-Leopoldshafen, Germany.
Markus
M
Reischl
Venetian Institute of Molecular Medicine; Padova, Italy.
Silvia
S
Carnio
Department of Integrative Pathophysiology; Universitätsmedizin Mannheim; Mannheim, Germany.
Dittmar
D
Labeit
Venetian Institute of Molecular Medicine; Padova, Italy.
Marco
M
Sandri
Department of Integrative Pathophysiology; Universitätsmedizin Mannheim; Mannheim, Germany.
Siegfried
S
Labeit
Institute of Toxicology and Genetics; Karlsruhe Institute of Technology; Eggenstein-Leopoldshafen, Germany; Institute of Molecular and Cell Biology; University of Applied Sciences Mannheim; Mannheim, Germany; Institute of Medical Technology; University of Heidelberg and University of Applied Sciences Mannheim; Mannheim, Germany.
Rüdiger
R
Rudolf
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000596:Amino Acids / Q000172:deficiency; D000818:Animals; D001343:Autophagy; D015415:Biomarkers / Q000378:metabolism; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D005215:Fasting; D005455:Fluorescent Antibody Technique; D006360:Heat-Shock Proteins / Q000378:metabolism*; D007553:Isotope Labeling; D008247:Lysosomes / Q000378:metabolism; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009121:Muscle Denervation; D009124:Muscle Proteins / Q000378:metabolism*; D009132:Muscles / Q000294:innervation / Q000378:metabolism / Q000473:pathology; D009469:Neuromuscular Junction / Q000378:metabolism; D010588:Phagosomes / Q000378:metabolism; D055550:Protein Stability; D011978:Receptors, Nicotinic / Q000378:metabolism*; D000071456:Sequestosome-1 Protein; D013569:Synapses / Q000378:metabolism; D000070584:Tripartite Motif Proteins; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D015854:Up-Regulation
D048868:Adaptor Proteins, Signal Transducing; D000596:Amino Acids; D015415:Biomarkers; D006360:Heat-Shock Proteins; C480860:Map1lc3b protein, mouse; D008869:Microtubule-Associated Proteins; D009124:Muscle Proteins; D011978:Receptors, Nicotinic; D000071456:Sequestosome-1 Protein; C486100:Sh3glb1 protein, mouse; C101343:Sqstm1 protein, mouse; D000070584:Tripartite Motif Proteins; C499084:Trim63 protein, mouse; D044767:Ubiquitin-Protein Ligases
Bif-1; LC3; MuRF1; SQSTM1/p62; acetylcholine receptor; atrophy; endophilin B1; neuromuscular junction; selective autophagy