Cryo-EM structure of mouse TRPML2 in lipid nanodiscs

Structural mechanism of human HCN1 hyperpolarization-activated channel inhibition by ivabradine

The hyperpolarization-activated cyclic nucleotide-gated (HCN) channels play a crucial role in regulating neuronal excitability. Despite growing evidence supporting the therapeutic potential of HCN1 inhibition in treating neurological disorders, the structural basis of channel inhibition by inhibitor has remained elusive. Here, we present the cryo-electron microscopy structure of human HCN1 channel in complex with inhibitor ivabradine, the drug on the market that acts on HCN channels. Combining electrophysiology, mutagenesis, and molecular dynamics simulations, our findings reveal that ivabradine binds to a previously unidentified pocket formed between the S4, S1, and HCN domain. Furthermore, through structure-based virtual screening, we identify two Food and Drug Administration-approved drugs that can inhibit the HCN1 channel by interacting with the ivabradine-binding site. Our results not only provide insights into the structural intricacies of ivabradine-mediated inhibition, but also offer a potential pharmacological framework for developing novel drugs targeting the HCN1 channel. The elucidation of these molecular interactions serves as a foundational step in advancing therapeutic strategies for modulating HCN1 activity, contributing to the broader landscape of drug discovery and development in this area.

Mutation of TRPML1 Channel and Pathogenesis of Neurodegeneration in Haimeria

Neurodegenerative diseases, a group of debilitating disorders, have garnered increasing attention due to their escalating prevalence, particularly among aging populations. Alzheimer's disease (AD) reigns as a prominent exemplar within this category, distinguished by its relentless progression of cognitive impairment and the accumulation of aberrant protein aggregates within the intricate landscape of the brain. While the intricate pathogenesis of neurodegenerative diseases has been the subject of extensive investigation, recent scientific inquiry has unveiled a novel player in this complex scenario-transient receptor potential mucolipin 1 (TRPML1) channels. This comprehensive review embarks on an exploration of the intricate interplay between TRPML1 channels and neurodegenerative diseases, with an explicit spotlight on Alzheimer's disease. It immerses itself in the intricate molecular mechanisms governing TRPML1 channel functionality and elucidates their profound implications for the well-being of neurons. Furthermore, the review ventures into the realm of therapeutic potential, pondering the possibilities and challenges associated with targeting TRPML1 channels as a promising avenue for the amelioration of neurodegenerative disorders. As we traverse this multifaceted terrain of neurodegeneration and the enigmatic role of TRPML1 channels, we embark on a journey that not only broadens our understanding of the intricate machinery governing neuronal health but also holds promise for the development of innovative therapeutic interventions in the relentless battle against neurodegenerative diseases.

The ion channels of endomembranes

The endomembrane system consists of organellar membranes in the biosynthetic pathway [endoplasmic reticulum (ER), Golgi apparatus, and secretory vesicles] as well as those in the degradative pathway (early endosomes, macropinosomes, phagosomes, autophagosomes, late endosomes, and lysosomes). These endomembrane organelles/vesicles work together to synthesize, modify, package, transport, and degrade proteins, carbohydrates, and lipids, regulating the balance between cellular anabolism and catabolism. Large ion concentration gradients exist across endomembranes: Ca2+ gradients for most endomembrane organelles and H+ gradients for the acidic compartments. Ion (Na+, K+, H+, Ca2+, and Cl-) channels on the organellar membranes control ion flux in response to cellular cues, allowing rapid informational exchange between the cytosol and organelle lumen. Recent advances in organelle proteomics, organellar electrophysiology, and luminal and juxtaorganellar ion imaging have led to molecular identification and functional characterization of about two dozen endomembrane ion channels. For example, whereas IP3R1-3 channels mediate Ca2+ release from the ER in response to neurotransmitter and hormone stimulation, TRPML1-3 and TMEM175 channels mediate lysosomal Ca2+ and H+ release, respectively, in response to nutritional and trafficking cues. This review aims to summarize the current understanding of these endomembrane channels, with a focus on their subcellular localizations, ion permeation properties, gating mechanisms, cell biological functions, and disease relevance.

Coordinating activation of endo-lysosomal two-pore channels and TRP mucolipins

Two-pore channels and TRP mucolipins are ubiquitous endo-lysosomal cation channels of pathophysiological relevance. Both are Ca2+-permeable and regulated by phosphoinositides, principally PI(3,5)P2. Accumulating evidence has uncovered synergistic channel activation by PI(3,5)P2 and endogenous metabolites such as the Ca2+ mobilizing messenger NAADP, synthetic agonists including approved drugs and physical cues such as voltage and osmotic pressure. Here, we provide an overview of this coordination.

Polycystin Channel Complexes

Polycystin subunits can form hetero- and homotetrameric ion channels in the membranes of various compartments of the cell. Homotetrameric polycystin channels are voltage- and calcium-modulated, whereas heterotetrameric versions are proposed to be ligand- or autoproteolytically regulated. Their importance is underscored by variants associated with autosomal dominant polycystic kidney disease and by vital roles in fertilization and embryonic development. The diversity in polycystin assembly and subcellular distribution allows for a multitude of sensory functions by this class of channels. In this review, we highlight their recent structural and functional characterization, which has provided a molecular blueprint to investigate the conformational changes required for channel opening in response to unique stimuli. We consider each polycystin channel type individually, discussing how they contribute to sensory cell biology, as well as their impact on the physiology of various tissues.