title: Glutamate-induced declustering of post-synaptic adaptor protein Cupidin (Homer 2/vesl-2) in cultured cerebellar granule cells.
abstract: Cupidin (Homer 2/vesl-2) is a post-synaptic adaptor protein that associates with glutamate receptor complexes and the actin cytoskeleton. We analyzed the developmental and activity-dependent localization of Cupidin in mouse cerebellar granule cells. Cupidin is predominantly localized to granule cell post-synapses connecting with mossy fiber terminals in developing post-natal cerebellum, but is diminished in adult cerebellum. In cultured granule cells 7 days in vitro, Cupidin was present as synaptic and extra-synaptic punctate clusters that largely co-localized with the actin-cytoskeletal binding partners F-actin and drebrin, as well as a post-synaptic scaffold protein PSD-95. Upon stimulation with glutamate, Cupidin clusters were rapidly dissociated without protein degradation, and by short-term but not sustained stimulation they were recovered after post-incubation without glutamate. The glutamate-induced declustering of Cupidin preceded that of F-actin and drebrin, was elicited by NMDA receptor-mediated Ca2+ influx, and was followed by a downstream pathway including MAPK/ERK and protein tyrosine kinase. Specific isoforms with post-translational modification were reduced depending on Ca2+-dependent protein phosphatase activity. In cultured hippocampal neurons, Homer family members Homer 1, Cupidin/Homer 2 and Homer 3 showed similar glutamate-induced declustering. We suggest that Cupidin acts as a mobile adaptor protein that changes the distribution states, clustered versus declustered, in response to synaptic activity.
mesh_terms: D000199:Actins / Q000378:metabolism; D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology; D018698:Glutamic Acid / Q000494:pharmacology*; D006624:Hippocampus / Q000166:cytology; D000072233:Homer Scaffolding Proteins; D046911:Macromolecular Substances; D051379:Mice; D008813:Mice, Inbred ICR; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009479:Neuropeptides / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D011485:Protein Binding / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000378:metabolism; D013569:Synapses / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D000199:Actins; D033942:Adaptor Proteins, Vesicular Transport; D002352:Carrier Proteins; D000072233:Homer Scaffolding Proteins; C000606625:Homer2 protein, mouse; D046911:Macromolecular Substances; D009479:Neuropeptides; D016194:Receptors, N-Methyl-D-Aspartate; C053386:drebrins; D018698:Glutamic Acid; D020928:Mitogen-Activated Protein Kinases; D002118:Calcium