title: Calcineurin inhibitor protein (CAIN) attenuates Group I metabotropic glutamate receptor endocytosis and signaling.
abstract: Group I metabotropic glutamate receptors (mGluRs) are coupled via phospholipase Cbeta to the hydrolysis of phosphoinositides and function to modulate neuronal excitability and synaptic transmission at glutamatergic synapses. The desensitization of Group I mGluR signaling is thought to be mediated primarily via second messenger-dependent protein kinases and G protein-coupled receptor kinases. We show here that both mGluR1 and mGluR5 interact with the calcineurin inhibitor protein (CAIN). CAIN is co-immunoprecipitated in a complex with Group I mGluRs from both HEK 293 cells and mouse cortical brain lysates. Purified CAIN and its C-terminal domain specifically interact with glutathione S-transferase fusion proteins corresponding to the second intracellular loop and the distal C-terminal tail domains of mGluR1. The interaction of CAIN with mGluR1 could also be blocked using a Tat-tagged peptide corresponding to the mGluR1 second intracellular loop domain. Overexpression of full-length CAIN attenuates the agonist-stimulated endocytosis of both mGluR1a and mGluR5a in HEK 293 cells, but expression of the CAIN C-terminal domain does not alter mGluR5a internalization. In contrast, overexpression of either full-length CAIN or the CAIN C-terminal domain impairs agonist-stimulated inositol phosphate formation in HEK 293 cells expressing mGluR1a. This CAIN-mediated antagonism of mGluR1a signaling appears to involve the disruption of receptor-Galpha(q/11) complexes. Taken together, these observations suggest that the association of CAIN with intracellular domains involved in mGluR/G protein coupling provides an additional mechanism by which Group I mGluR endocytosis and signaling are regulated.
authors.affiliation: J. Allyn Taylor Centre for Cell Biology, Molecular Brain Research Group, Robarts Research Institute, Ontario N6A 5K8, Canada.
authors.forename: Lucimar T
authors.initials: LT
authors.lastname: Ferreira
authors.forename: Lianne B
authors.initials: LB
authors.lastname: Dale
authors.forename: Fabiola M
authors.initials: FM
authors.lastname: Ribeiro
authors.forename: Andy V
authors.initials: AV
authors.lastname: Babwah
authors.forename: Macarena
authors.initials: M
authors.lastname: Pampillo
authors.forename: Stephen S G
authors.initials: SS
authors.lastname: Ferguson
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D019703:Calcineurin / Q000737:chemistry / Q000502:physiology*; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D004705:Endocytosis; D006801:Humans; D007295:Inositol Phosphates / Q000737:chemistry; D008856:Microscopy, Fluorescence / Q000379:methods; D008954:Models, Biological; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D011493:Protein Kinase C / Q000378:metabolism; D017434:Protein Structure, Tertiary; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C491861:CABIN1 protein, human; D007295:Inositol Phosphates; D018094:Receptors, Metabotropic Glutamate; D011493:Protein Kinase C; D019703:Calcineurin; D002118:Calcium