Role of Spinophilin in Group I Metabotropic Glutamate Receptor Endocytosis, Signaling, and Synaptic Plasticity

Andrea R. Di Sebastiano; Sandra Fahim; Henry A. Dunn; Cornelia Walther; Fabiola M. Ribeiro; Sean P. Cregan; Stephane Angers; Susanne Schmid; Stephen S. G. Ferguson

doi:10.1074/jbc.M116.722355

Role of Spinophilin in Group I Metabotropic Glutamate Receptor Endocytosis, Signaling, and Synaptic Plasticity*

From the ^‡J. Allyn Taylor Centre for Cell Biology, Robarts Research Institute, London, Ontario N6A 3K7, Canada,
the ^¶Departamento de Bioquimica e Imunologia, ICB, Universidade Federa de Minas Gerais, Belo Horizonte 31270-901, Brazil,
the ^‖Leslie Dan Faculty of Pharmacy and Department of Pharmacology, University of Toronto, Toronto, Ontario M5S 3M2, Canada,
the ^**Department of Anatomy and Cell Biology, University of Western Ontario, London, Ontario N6A 3K7, Canada, and
the ^§Department of Cellular and Molecular Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada

↵1 A Career Investigator of the Heart and Stroke Foundation of Ontario and Tier I Canada Research Chair in Brain and Mind. To whom correspondence should be addressed: Dept. of Cellular and Molecular Medicine, University of Ottawa, 451 Smyth Dr., Ottawa, Ontario K1H 8M5, Canada. Tel.: 613-562-5800 (ext. 8889); E-mail: sferguso{at}uottawa.ca.

Abstract

Activation of Group I metabotropic glutamate receptors (mGluRs) activates signaling cascades, resulting in calcium release from intracellular stores, ERK1/2 activation, and long term changes in synaptic activity that are implicated in learning, memory, and neurodegenerative diseases. As such, elucidating the molecular mechanisms underlying Group I mGluR signaling is important for understanding physiological responses initiated by the activation of these receptors. In the current study, we identify the multifunctional scaffolding protein spinophilin as a novel Group I mGluR-interacting protein. We demonstrate that spinophilin interacts with the C-terminal tail and second intracellular loop of Group I mGluRs. Furthermore, we show that interaction of spinophilin with Group I mGluRs attenuates receptor endocytosis and phosphorylation of ERK1/2, an effect that is dependent upon the interaction of spinophilin with the C-terminal PDZ binding motif encoded by Group I mGluRs. Spinophilin knock-out results in enhanced mGluR5 endocytosis as well as increased ERK1/2, AKT, and Ca²⁺ signaling in primary cortical neurons. In addition, the loss of spinophilin expression results in impaired mGluR5-stimulated LTD. Our results indicate that spinophilin plays an important role in regulating the activity of Group I mGluRs as well as their influence on synaptic activity.

Footnotes

↵* This work was supported by Canadian Institutes of Health Research Grant MOP-119437 (to S. S. G. F.). The authors declare that they have no conflicts of interest with the contents of this article.