Biology subjects

Abderemane-Ali, F.

Publications and source records attributed to Abderemane-Ali, F..

3 recordsLinked to original sources

bioRxiv2024

Structure of the human K2P13.1(THIK-1) channel reveals a novel hydrophilic pore restriction and lipid cofactor site

The halothane-inhibited K2P leak potassium channel K2P13.1 (THIK-1)1-3 is found in diverse cells1,4 including neurons1,5 and microglia6-8 where it affects surveillance6, synaptic pruning7, phagocytosis7, and inflammasome-mediated interleukin-1{beta} release6,8,9. As with many K2Ps1,5,10-14 and other voltage-gated ion channel (VGIC) superfamily members3,15,16, polyunsaturated fatty acid (PUFA) lipids modulate K2P13.1 (THIK-1)1,5,14,17 via a poorly understood mechanism. Here, we present cryo-electronmicroscopy (cryo-EM) structures of human K2P13.1 (THIK-1) and mutants in lipid nanodiscs and detergent. These reveal that, unlike other K2Ps13,18-24, K2P13.1 (THIK-1) has a two-chamber aqueous inner cavity obstructed by a M4 transmembrane helix tyrosine (Tyr273, the flow restrictor). This hydrophilic barrier can be opened by an activatory mutation, S136P25, at natural break in the M2 transmembrane helix and by intrinsic channel dynamics. The structures also reveal a buried lipid in the P1/M4 intersubunit interface at a location, the PUFA site, that coincides with the TREK subfamily K2P modulator pocket for small molecule agonists18,26,27. This overlap, together with the effects of mutation on K2P13.1 (THIK-1) PUFA responses, indicates that the PUFA site lipids are K2P13.1 (THIK-1) cofactors. Comparison with the PUFA-responsive VGIC Kv7.1 (KCNQ1)28-31 reveals a shared role for the equivalent pore domain intersubunit interface in lipid modulation, providing a framework for dissecting the effects of PUFAs on the VGIC superfamily. Our findings reveal the unique architecture underlying K2P13.1 (THIK-1) function, highlight the importance of the P1/M4 interface in control of K2Ps by both natural and synthetic agents, and should aid development of THIK subfamily modulators for diseases such as neuroinflammation6,32 and autism6.

biophysics↗

bioRxiv2022

EMC holdase:CaV1.2/CaVβ3 complex and CaV1.2 channel structures reveal CaV assembly and drug binding mechanisms

Voltage-gated ion channels (VGICs) comprise multiple structural units whose assembly is required for function1,2. There is scant structural understanding of how VGIC subunits assemble and whether chaperone proteins are required. High-voltage activated calcium channels (CaVs)3,4 are paradigmatic multi-subunit VGICs from electrically excitable tissues whose function and trafficking is powerfully shaped by interactions between pore-forming CaV1 or CaV2 CaV13 and auxiliary CaV{beta}5, and CaV2{delta} subunits6,7. Here, we present cryo-EM structures of human brain and cardiac CaV1.2 bound with CaV{beta}3 to a chaperone, the endoplasmic reticulum membrane protein complex (EMC)8,9, and of the isolated CaV1.2/CaV{beta}3/CaV2{delta}-1 channel. These provide an unprecedented view of an EMC holdase:client complex and define EMC sites, the TM and Cyto docks, whose interaction with the client channel cause partial extraction of a pore subunit and splay open the CaV2{delta} interaction site. The structures further identify the CaV2{delta} binding site for gabapentinoid anti-pain and anti-anxiety drugs6, show that EMC and CaV2{delta} channel interactions are mutually exclusive, and indicate that EMC to CaV2{delta} handoff involves a Ca2+-dependent step and ordering of multiple CaV1.2 elements. Together, the structures unveil a CaV assembly intermediate and previously unknown EMC client binding sites that have broad implications for biogenesis of VGICs and other membrane proteins.

biophysics↗

bioRxiv2022

Definition of a saxitoxin (STX) binding code enables discovery and characterization of the Anuran saxiphilin family

American bullfrog (Rana castesbeiana) saxiphilin (RcSxph) is a high-affinity toxin sponge protein thought to prevent intoxication by saxitoxin (STX), a lethal bis-guanidinium neurotoxin that causes paralytic shellfish poisoning (PSP) by blocking voltage-gated sodium channels (NaVs). How specific RcSxph interactions contribute to STX binding has not been defined and whether other organisms have similar proteins is unclear. Here, we use mutagenesis, ligand binding, and structural studies to define the energetic basis of Sxph:STX recognition. The resultant STX recognition code enabled engineering of RcSxph to improve its ability to rescue NaVs from STX and facilitated discovery of ten new frog and toad Sxphs. Definition of the STX binding code and Sxph family expansion among diverse Anurans separated by [~]140 million years of evolution provides a molecular basis for understanding the roles of toxin sponge proteins in toxin resistance and for developing novel proteins to sense or neutralize STX and related PSP toxins. TeaserA conserved STX recognition motif from frog and toad saxiphilins defines molecular principles of paralytic toxin binding.

biophysics↗