title: Optogenetic approaches addressing extracellular modulation of neural excitability.
abstract: The extracellular ionic environment in neural tissue has the capacity to influence, and be influenced by, natural bouts of neural activity. We employed optogenetic approaches to control and investigate these interactions within and between cells, and across spatial scales. We began by developing a temporally precise means to study microdomain-scale interactions between extracellular protons and acid-sensing ion channels (ASICs). By coupling single-component proton-transporting optogenetic tools to ASICs to create two-component optogenetic constructs (TCOs), we found that acidification of the local extracellular membrane surface by a light-activated proton pump recruited a slow inward ASIC current, which required molecular proximity of the two components on the membrane. To elicit more global effects of activity modulation on 'bystander' neurons not under direct control, we used densely-expressed depolarizing (ChR2) or hyperpolarizing (eArch3.0, eNpHR3.0) tools to create a slow non-synaptic membrane current in bystander neurons, which matched the current direction seen in the directly modulated neurons. Extracellular protons played contributory role but were insufficient to explain the entire bystander effect, suggesting the recruitment of other mechanisms. Together, these findings present a new approach to the engineering of multicomponent optogenetic tools to manipulate ionic microdomains, and probe the complex neuronal-extracellular space interactions that regulate neural excitability.
authors.affiliation: Bioengineering, Stanford University, 318 Campus Drive, Stanford, CA 94305, USA.|Neurosciences, Stanford University, 318 Campus Drive, Stanford, CA 94305, USA.
authors.forename: Emily A
authors.initials: EA
authors.lastname: Ferenczi
authors.affiliation: Institute of Biology, Experimental Biophysics, Invalidenstraße 42, D-10115 Berlin, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Vierock
authors.affiliation: Institute of Biology, Experimental Biophysics, Invalidenstraße 42, D-10115 Berlin, Germany.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Atsuta-Tsunoda
authors.affiliation: Institute of Biology, Experimental Biophysics, Invalidenstraße 42, D-10115 Berlin, Germany.
authors.forename: Satoshi P
authors.initials: SP
authors.lastname: Tsunoda
authors.affiliation: Bioengineering, Stanford University, 318 Campus Drive, Stanford, CA 94305, USA.
authors.forename: Charu
authors.initials: C
authors.lastname: Ramakrishnan
authors.affiliation: Bioengineering, Stanford University, 318 Campus Drive, Stanford, CA 94305, USA.
authors.forename: Christopher
authors.initials: C
authors.lastname: Gorini
authors.affiliation: Bioengineering, Stanford University, 318 Campus Drive, Stanford, CA 94305, USA.
authors.forename: Kimberly
authors.initials: K
authors.lastname: Thompson
authors.affiliation: Bioengineering, Stanford University, 318 Campus Drive, Stanford, CA 94305, USA.
authors.forename: Soo Yeun
authors.initials: SY
authors.lastname: Lee
authors.affiliation: Bioengineering, Stanford University, 318 Campus Drive, Stanford, CA 94305, USA.
authors.forename: Andre
authors.initials: A
authors.lastname: Berndt
authors.affiliation: Bioengineering, Stanford University, 318 Campus Drive, Stanford, CA 94305, USA.
authors.forename: Chelsey
authors.initials: C
authors.lastname: Perry
authors.affiliation: Institute of Biology, Experimental Biophysics, Invalidenstraße 42, D-10115 Berlin, Germany.
authors.forename: Sonja
authors.initials: S
authors.lastname: Minniberger
authors.affiliation: Institute of Biology, Experimental Biophysics, Invalidenstraße 42, D-10115 Berlin, Germany.
authors.forename: Arend
authors.initials: A
authors.lastname: Vogt
authors.affiliation: Bioengineering, Stanford University, 318 Campus Drive, Stanford, CA 94305, USA.|Neurosciences, Stanford University, 318 Campus Drive, Stanford, CA 94305, USA.
authors.forename: Joanna
authors.initials: J
authors.lastname: Mattis
authors.affiliation: Bioengineering, Stanford University, 318 Campus Drive, Stanford, CA 94305, USA.|Neurosciences, Stanford University, 318 Campus Drive, Stanford, CA 94305, USA.
authors.forename: Rohit
authors.initials: R
authors.lastname: Prakash
authors.affiliation: Bioengineering, Stanford University, 318 Campus Drive, Stanford, CA 94305, USA.
authors.forename: Scott
authors.initials: S
authors.lastname: Delp
authors.affiliation: Bioengineering, Stanford University, 318 Campus Drive, Stanford, CA 94305, USA.|HHMI, Stanford University, 318 Campus Drive, Stanford, CA 94305, USA.|Department of Psychiatry &Behavioral Science, Stanford University, 401 Quarry Road, Stanford, CA 94305, USA.
authors.forename: Karl
authors.initials: K
authors.lastname: Deisseroth
authors.affiliation: Institute of Biology, Experimental Biophysics, Invalidenstraße 42, D-10115 Berlin, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Hegemann
mesh_terms: D062565:Acid Sensing Ion Channels / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000737:chemistry; D005110:Extracellular Space / Q000737:chemistry; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008027:Light; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008959:Models, Neurological; D009474:Neurons / Q000502:physiology*; D009865:Oocytes / Q000166:cytology; D062308:Optogenetics; D018408:Patch-Clamp Techniques; D011522:Protons; D013997:Time Factors; D014982:Xenopus laevis
chemical_list: D062565:Acid Sensing Ion Channels; D011522:Protons; D002118:Calcium