Rowland, A. | Search bioRxiv

bioRxiv2024

CryoEM Structure of the human THIK-1 K2P K+ Channel Reveals a Lower 'Y-gate' Regulated by Lipids and Anaesthetics

THIK-1 (KCNK13) is a halothane-inhibited and anionic lipid-activated Two-Pore Domain (K2P) K+ channel implicated in microglial activation and neuroinflammation, and a current target for the treatment of neurodegenerative disorders such as Alzheimers and Amyothropic Lateral Sclerosis (ALS). However, compared to other K2P channels, little is known about the structural and functional properties of THIK-1. Here we present a 3.16 [A] resolution cryoEM structure of human THIK-1 that reveals several unique features, in particular, a tyrosine in M4 (Y273) which contributes to a lower Y-gate that opens upon activation by physiologically-relevant signalling pathways. We further demonstrate that binding of linoleic acid within a modulatory pocket adjacent to the filter also activates THIK-1, and that halothane inhibition involves a binding site within the inner cavity resulting in changes to the Y-gate. Finally, the extracellular cap domain contains positively-charged residues that line the ion exit pathway and which contribute to the unique biophysical properties of this channel. Overall, our results provide important insights into the structural basis of THIK1 function and identify distinct regulatory sites that expand its potential as a drug target for the modulation of microglial function.

biophysics↗

bioRxiv2022

A metabolite sensor subunit of the Atg1/ULK complex regulates selective autophagy

Cells convert complex metabolic information into stress-adapted autophagy responses. Canonically, multilayered protein kinase networks converge on the conserved Atg1/ULK kinase complex (AKC) to induce non-selective and selective forms of autophagy in response to metabolic changes. Here, we show that, upon phosphate starvation, the metabolite sensor Pho81 interacts with the adaptor subunit Atg11 at the AKC via an Atg11/FIP200 interaction motif to modulate pexophagy by virtue of its conserved phospho-metabolite sensing SPX domain. Notably, we find core AKC components Atg13 and Atg17 are dispensable for phosphate starvation-induced autophagy revealing significant compositional and functional plasticity of the AKC. Our data indicate that, instead of functioning as a selective autophagy receptor, Pho81 compensates for partially inactive Atg13 during pexophagy when TORC1 remains active under phosphate starvation. Our work shows Atg11/FIP200 adaptor subunits not only bind selective autophagy receptors but also modulator subunits that convey metabolic information directly to the AKC for autophagy regulation.

cell biology↗