Substitution of 5-HT1A receptor signaling by a light-activated G protein-coupled receptor.
Understanding serotonergic (5-HT) signaling is critical for understanding human physiology, behavior, and neuropsychiatric disease. 5-HT mediates its actions via ionotropic and metabotropic 5-HT receptors. The 5-HT(1A) receptor is a metabotropic G protein-coupled receptor linked to the G(i/o) signaling pathway and has been specifically implicated in the pathogenesis of depression and anxiety. To understand and precisely control 5-HT(1A) signaling, we created a light-activated G protein-coupled receptor that targets into 5-HT(1A) receptor domains and substitutes for endogenous 5-HT(1A) receptors. To induce 5-HT(1A)-like targeting, vertebrate rhodopsin was tagged with the C-terminal domain (CT) of 5-HT(1A) (Rh-CT(5-HT1A)). Rh-CT(5-HT1A) activates G protein-coupled inward rectifying K(+) channels in response to light and causes membrane hyperpolarization in hippocampal neurons, similar to the agonist-induced responses of the 5-HT(1A) receptor. The intracellular distribution of Rh-CT(5-HT1A) resembles that of the 5-HT(1A) receptor; Rh-CT(5-HT1A) localizes to somatodendritic sites and is efficiently trafficked to distal dendritic processes. Additionally, neuronal expression of Rh-CT(5-HT1A), but not Rh, decreases 5-HT(1A) agonist sensitivity, suggesting that Rh-CT(5-HT1A) and 5-HT(1A) receptors compete to interact with the same trafficking machinery. Finally, Rh-CT(5-HT1A) is able to rescue 5-HT(1A) signaling of 5-HT(1A) KO mice in cultured neurons and in slices of the dorsal raphe showing that Rh-CT(5-HT1A) is able to functionally compensate for native 5-HT(1A). Thus, as an optogenetic tool, Rh-CT(5-HT1A) has the potential to directly correlate in vivo 5-HT(1A) signaling with 5-HT neuron activity and behavior in both normal animals and animal models of neuropsychiatric disease.
Oh
Eugene
E
Department of Neurosciences, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA.
Maejima
Takashi
T
Liu
Chen
C
Deneris
Evan
E
Herlitze
Stefan
S
D000818:Animals; D002460:Cell Line; D003712:Dendrites / Q000378:metabolism*; D006624:Hippocampus / Q000378:metabolism*; D006801:Humans; D001523:Mental Disorders / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009422:Nervous System Diseases / Q000235:genetics / Q000378:metabolism; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport; D051381:Rats; D044282:Receptor, Serotonin, 5-HT1A / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012243:Rhodopsin / Q000235:genetics / Q000378:metabolism*
D024661:Potassium Channels, Inwardly Rectifying; D011993:Recombinant Fusion Proteins; D044282:Receptor, Serotonin, 5-HT1A; D012243:Rhodopsin