A disulphide-linked heterodimer of TWIK-1 and TREK-1 mediates passive conductance in astrocytes

Abstract

TWIK-1 is a member of the two-pore domain K þ (K2P) channel family that plays an essential part in the regulation of resting membrane potential and cellular excitability. The physiological role of TWIK-1 has remained enigmatic because functional expression of TWIK-1 channels is elusive. Here we report that native TWIK-1 forms a functional channel at the plasma membrane of astrocytes. A search for TWIK-1-binding proteins led to the identification of TREK-1, another member of the K2P family. The TWIK-1/TREK-1 heterodimeric channel is formed via a disulphide bridge between residue C69 in TWIK-1 and C93 in TREK-1. Gene silencing demonstrates that surface expression of TWIK-1 and TREK-1 are interdependent. TWIK-1/TREK-1 heterodimers mediate astrocytic passive conductance and cannabinoidinduced glutamate release from astrocytes. Our study sheds new light on the diversity of K2P channels.

Cografting astrocytes improves cell therapeutic outcomes in a Parkinson’s disease model

“…Nigral mDA neurons in the midbrain physiologically receive glutamatergic excitatory and GABAergic inhibitory synaptic inputs from several regions of the brain (35). Excitatory postsynaptic density protein 95 (PSD95) clusters were found on dendritic shafts of TH + DA neuronal cells, and astrocytes cultured from cortices in this study (DIV14) exhibited current (2577 ± 401.1 pA, n = 16) and conductance (23.08 ± 3.306 nS, n = 16) that were significantly lower than those detected in cortical slices in vivo (40 nS) (23,24). Interestingly, the current and conductance values of astrocytes cultured from VM at DIV14 were even lower compared with the cultured Ctx-Ast at DIV14, and those of VM-Ast increased after a longer culture period (at DIV35) (Supplemental Figure 1, D and E).…”

“…Along with abundant cells immunoreactive for the immature astrocytic markers GLAST and Sox2, the expression levels of the immature astrocytic genes (Sox2, Nestin, GLAST, and vimentin) in the RNAsequencing (RNA-seq) data were high (fragments per kilobase of exons per million reads [FPKM]: 94-4180, Supplemental Figure 1C), indicating that the astrocytes cultured in this study had immature properties. Previous studies have reported that astrocytes in culture were electrophysiologically immature compared with those in vivo (23,24). Consistently, in patch-clamp analyses, mDA neurons are developed and reside (hereafter referred as dopaminergic), greatly support a series of NPC behaviors associated with their therapeutic capacity upon transplantation, such as mDA neuron differentiation, synaptic maturation, midbrainspecific marker expression, presynaptic DA neuron function, and resistance against toxic stimuli.…”

The Nucleus Accumbens: Mechanisms of Addiction across Drug Classes Reflect the Importance of Glutamate Homeostasis

“…When secreted, eCBs originate from the postsynaptic neuron and travel retrogradely to the presynaptic terminal, activate CB1 receptors, and cause a decrease in glutamate release probability (Lupica and Riegel, 2005;Szabo and Schlicker, 2005;Hoffman and Lupica, 2013). Recent studies also support a role for astroglial CB1 receptors in the enhancement of glial glutamate release, which can modulate plasticity in adjacent synapses (Navarrete and Araque, 2008;Rossi, 2012;Hwang et al, 2014).…”

Formation of Functional Heterodimers by TREK-1 and TREK-2 Two-pore Domain Potassium Channel Subunits

“…In this study TWIK-1 and TREK-1 coexpression served as a negative control, as no sign of interaction was found between these two subunits. In contrast, TWIK-1/TREK-1 heteromerization was reported by another group in hippocampal astrocytes (15). Quite unexpectedly, activation of a G i -protein-coupled receptor was claimed to convert the heterodimer into an anion conductive channel (15); the authors have suggested that the binding of the ␤␥ subunits to the heterodimer induces channel pore dilation resulting in glutamate permeability.…”