title: TREK-1 and Best1 channels mediate fast and slow glutamate release in astrocytes upon GPCR activation.
abstract: Astrocytes release glutamate upon activation of various GPCRs to exert important roles in synaptic functions. However, the molecular mechanism of release has been controversial. Here, we report two kinetically distinct modes of nonvesicular, channel-mediated glutamate release. The fast mode requires activation of G(αi), dissociation of G(βγ), and subsequent opening of glutamate-permeable, two-pore domain potassium channel TREK-1 through direct interaction between G(βγ) and N terminus of TREK-1. The slow mode is Ca(2+) dependent and requires G(αq) activation and opening of glutamate-permeable, Ca(2+)-activated anion channel Best1. Ultrastructural analyses demonstrate that TREK-1 is preferentially localized at cell body and processes, whereas Best1 is mostly found in microdomains of astrocytes near synapses. Diffusion modeling predicts that the fast mode can target neuronal mGluR with peak glutamate concentration of 100 μM, whereas slow mode targets neuronal NMDA receptors at around 1 μM. Our results reveal two distinct sources of astrocytic glutamate that can differentially influence neighboring neurons.
authors.affiliation: Center for Neural Science, Korea Institute of Science and Technology, Seoul, Republic of Korea.
authors.forename: Dong Ho
authors.initials: DH
authors.lastname: Woo
authors.forename: Kyung-Seok
authors.initials: KS
authors.lastname: Han
authors.forename: Jae Wan
authors.initials: JW
authors.lastname: Shim
authors.forename: Bo-Eun
authors.initials: BE
authors.lastname: Yoon
authors.forename: Eunju
authors.initials: E
authors.lastname: Kim
authors.forename: Jin Young
authors.initials: JY
authors.lastname: Bae
authors.forename: Soo-Jin
authors.initials: SJ
authors.lastname: Oh
authors.forename: Eun Mi
authors.initials: EM
authors.lastname: Hwang
authors.forename: Alan D
authors.initials: AD
authors.lastname: Marmorstein
authors.forename: Yong Chul
authors.initials: YC
authors.lastname: Bae
authors.forename: Jae-Yong
authors.initials: JY
authors.lastname: Park
authors.forename: C Justin
authors.initials: CJ
authors.lastname: Lee
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D000075002:Bestrophins; D002478:Cells, Cultured; D005089:Exocytosis; D005136:Eye Proteins / Q000235:genetics / Q000378:metabolism*; D018698:Glutamic Acid / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D007473:Ion Channels / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D024683:Potassium Channels, Tandem Pore Domain / Q000235:genetics / Q000378:metabolism*; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D016415:Sequence Alignment; D015398:Signal Transduction
chemical_list: C491856:Best1 protein, mouse; D000075002:Bestrophins; D005136:Eye Proteins; D007473:Ion Channels; D024683:Potassium Channels, Tandem Pore Domain; D043562:Receptors, G-Protein-Coupled; C103742:potassium channel protein TREK-1; D018698:Glutamic Acid