Crosslinking-induced endocytosis of acetylcholine receptors by quantum dots

• Published in: PloS one Vol. 9; no. 2; p. e90187
• Main Authors: Lee, Chi Wai, Zhang, Hailong, Geng, Lin, Peng, H Benjamin
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 25.02.2014; Public Library of Science (PLoS)
• Subjects: Agrin; Agrin - metabolism; Animals; Antibodies; Biology; Biotin; Bungarotoxin; Caveolin; Cell surface; Clathrin; Clathrin - metabolism; Clusters; Cross-Linking Reagents - chemistry; Cross-Linking Reagents - pharmacology; Crosslinking; Dispersal; Embryos; Endocytosis; Endocytosis - drug effects; Endosomes; Fluorescence; Immunoglobulins; Integrity; Internalization; Kinases; Laboratories; Life sciences; Localization; Medicine; Mice; Microtubules - drug effects; Microtubules - metabolism; Molecular modelling; Muscles; Musculoskeletal system; MUSK protein; Myasthenia; Myasthenia gravis; Neuromuscular junctions; Neurosciences; Particle Size; Pathogenesis; Phosphatase; Physiology; Polymer crosslinking; Protein transport; Proteins; Quantum dots; Quantum Dots - chemistry; Receptor density; Receptor Protein-Tyrosine Kinases - metabolism; Receptors; Receptors, Cholinergic - chemistry; Receptors, Cholinergic - metabolism; Signal transduction; Signal Transduction - drug effects; Signaling; Streptavidin; Synapses - drug effects; Synapses - metabolism; Xenopus; Hong Kong; China
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0090187

In a majority of patients with myasthenia gravis (MG), anti-acetylcholine receptor (AChR) antibodies target postsynaptic AChR clusters and thus compromise the membrane integrity of neuromuscular junctions (NMJs) and lead to muscle weakness. Antibody-induced endocytosis of AChRs in the postsynaptic membrane represents the initial step in the pathogenesis of MG; however, the molecular mechanisms underlying AChR endocytosis remain largely unknown. Here, we developed an approach to mimic the pathogenic antibodies for inducing the crosslinking and internalization of AChRs from the postsynaptic membrane. Using biotin-α-bungarotoxin and quantum dot (QD)-streptavidin, cell-surface and internalized AChRs could be readily distinguished by comparing the size, fluorescence intensity, trajectory, and subcellular localization of the QD signals. QD-induced AChR endocytosis was mediated by clathrin-dependent and caveolin-independent mechanisms, and the trafficking of internalized AChRs in the early endosomes required the integrity of microtubule structures. Furthermore, activation of the agrin/MuSK (muscle-specific kinase) signaling pathway strongly suppressed QD-induced internalization of AChRs. Lastly, QD-induced AChR crosslinking potentiated the dispersal of aneural AChR clusters upon synaptic induction. Taken together, our results identify a novel approach to study the mechanisms of AChR trafficking upon receptor crosslinking and endocytosis, and demonstrate that agrin-MuSK signaling pathways protect against crosslinking-induced endocytosis of AChRs.