title: Receptor-selective diffusion barrier enhances sensitivity of astrocytic processes to metabotropic glutamate receptor stimulation.
abstract: Metabotropic glutamate receptor (mGluR)-dependent calcium ion (Ca²+) signaling in astrocytic processes regulates synaptic transmission and local blood flow essential for brain function. However, because of difficulties in imaging astrocytic processes, the subcellular spatial organization of mGluR-dependent Ca²+ signaling is not well characterized and its regulatory mechanism remains unclear. Using genetically encoded Ca²+ indicators, we showed that despite global stimulation by an mGluR agonist, astrocyte processes intrinsically exhibited a marked enrichment of Ca²+ responses. Immunocytochemistry indicated that these polarized Ca²+ responses could be attributed to increased density of surface mGluR5 on processes relative to the soma. Single-particle tracking of surface mGluR5 dynamics revealed a membrane barrier that blocked the movement of mGluR5 between the processes and the soma. Overexpression of mGluR or expression of its carboxyl terminus enabled diffusion of mGluR5 between the soma and the processes, disrupting the polarization of mGluR5 and of mGluR-dependent Ca²+ signaling. Together, our results demonstrate an mGluR5-selective diffusion barrier between processes and soma that compartmentalized mGluR Ca²+ signaling in astrocytes and may allow control of synaptic and vascular activity in specific subcellular domains.
authors.affiliation: Laboratory for Developmental Neurobiology, Brain Science Institute, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors.forename: Misa
authors.initials: M
authors.lastname: Arizono
authors.forename: Hiroko
authors.initials: H
authors.lastname: Bannai
authors.forename: Kyoko
authors.initials: K
authors.lastname: Nakamura
authors.forename: Fumihiro
authors.initials: F
authors.lastname: Niwa
authors.forename: Masahiro
authors.initials: M
authors.lastname: Enomoto
authors.forename: Toru
authors.initials: T
authors.lastname: Matsu-Ura
authors.forename: Akitoshi
authors.initials: A
authors.lastname: Miyamoto
authors.forename: Mark W
authors.initials: MW
authors.lastname: Sherwood
authors.forename: Takeshi
authors.initials: T
authors.lastname: Nakamura
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Mikoshiba
mesh_terms: D000465:Algorithms; D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects; D002147:Calmodulin / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D018920:Coculture Techniques; D004058:Diffusion; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D036681:Fluorescence Recovery After Photobleaching; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism; D007150:Immunohistochemistry; D007700:Kinetics; D009474:Neurons / Q000166:cytology / Q000378:metabolism*; D045663:Quantum Dots; D051381:Rats; D017208:Rats, Wistar; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012118:Resorcinols / Q000494:pharmacology; D014162:Transfection
chemical_list: D002147:Calmodulin; D018690:Excitatory Amino Acid Agonists; C578937:Grm5 protein, rat; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; D011993:Recombinant Fusion Proteins; D012118:Resorcinols; D049452:Green Fluorescent Proteins; C079215:3,5-dihydroxyphenylglycine; D002118:Calcium; D005998:Glycine