An inherited hypomorphic variant in PIEZO2 reveals structural features of mechanotransduction.

Piezo1 channel: structure, mechanogating mechanism, functions, diseases and therapeutic strategy

The Piezo1 channel is a mechanosensitive, non-selective cation channel that converts mechanical forces into electrochemical signals, playing pivotal roles in vertebrate physiology. Structurally, Piezo1 features a distinctive trimeric propeller structure that undergoes conformational changes in response to membrane tension, enabling mechanogating. Accordingly, Piezo1 is involved in a broad spectrum of physiological processes, including vascular development and homeostasis, bone and cartilage formation, skeletal muscle growth, neural development, sensory perception, immune regulation, and cellular volume regulation. Accumulating evidence indicates that mutations or dysregulation of Piezo1 are closely associated with a variety of human diseases, including genetic diseases, cardiovascular diseases, infectious diseases, autoimmune diseases, and cancer. Therefore, Piezo1 has emerged as a potential therapeutic target. Currently, the exploration of pharmacological modulators targeting Piezo1, as well as emerging approaches such as gene therapy, artificial intelligence (AI)-driven drug discovery, and advanced drug delivery systems, offer potential avenues for the development of Piezo1-targeted therapeutic strategies. However, these approaches still face significant challenges regarding specificity, in vivo targeting, and context-dependent effects. This review systematically summarizes the structure, mechanogating mechanisms, physiological and cellular functions of Piezo1, as well as its associations with human diseases. Based on this, the limitations of current Piezo1-targeted therapeutic strategies and their future developmental directions are highlighted, while the therapeutic potential of targeting Piezo1 is emphasized.

A Propeller with a Flexible Twist: A Computational Analysis of Intrinsically Disordered Regions in PIEZO Gating and PIEZO-Associated Channelopathies

Background: Mechanosensitive ion channels PIEZO1 and PIEZO2 are key mediators of mechanotransduction, which converts physical forces into cellular signals involved in proprioception, touch, vascular function, and other physiological processes. Mutations in human PIEZO proteins are linked to various diseases, such as hereditary xerocytosis, lymphatic dysplasia, and proprioceptive dysfunction. However, the role of intrinsic disorder in the regulation of these proteins and their susceptibility for disease-associated mutations remains unclear. Methods: We analyzed canonical human PIEZO1 and PIEZO2 protein sequences using machine learning, neural network, and energy-based disorder predictors, together with the prediction of disorder-mediated binding regions, phase separation propensity, interaction networks, evolutionary conservation, clinically annotated human variants, and peptide structural modeling. Results: Both proteins showed moderate intrinsic disorder, with PIEZO2 having slightly greater disorder propensity and higher predicted phase separation potential. Intrinsically disordered regions frequently overlapped binding-prone segments and post-translational modification sites, supporting regulatory functions. Evolutionary comparisons showed strong conservation of PIEZO proteins, while selected disordered regions retained disorder propensity despite greater sequence variability. Disease-causing variants mainly affected the ordered regions of both proteins, whereas disordered regions contained proportionally more benign variants and relatively few pathogenic mutations. The modeling of mutations within disordered hotspots showed altered local conformational tendencies, indicating that some disease variants may disrupt dynamic interaction interfaces rather than global structure. Interaction network analysis linked both proteins to enriched mechanotransduction, ion transport, and cytoskeletal pathways. Conclusions: Overall, our findings identify intrinsic disorder as an underappreciated feature of PIEZO channel biology and provide a framework for interpreting PIEZO-associated channelopathies. PIEZO proteins also perfectly illustrate the proteoform concept, where one gene yields a highly diverse kit of mechanosensitive molecular tools. While humans only have two primary PIEZO genes (PIEZO1 and PIEZO2), the body generates a vast array of functional variations.

Hypoglycosylation lowers the mechanical activation threshold of Piezo1 and enhances cortical neuronal mechanotransduction: implications for PMM2-CDG

Piezo1 is a mechanically activated cation channel whose N-linked glycans support protein maturation and plasma membrane trafficking, but their contribution to mechanical gating is unknown. We asked whether hypoglycosylation alters Piezo1 mechanosensitivity and cortical neuronal mechanotransduction, with potential relevance to neurological manifestations of congenital disorders of glycosylation (CDG). Human Piezo1 was studied in HEK293 cells after mutation of two conserved cap-domain N-glycosylation sites or inhibition of N-glycan maturation with swainsonine or kifunensine. Mechanically activated currents were recorded by cell-attached patch-clamp during incremental negative-pressure pulses, whereas Ca2+ responses were measured during uniaxial stretch. Piezo1 abundance, synaptic localisation and stretch-evoked Ca2+ signals were also examined in primary mouse cortical neurons. On poly-L-lysine, N2293Q or N2330Q shifted the pressure-response relationship towards lower activating pressures without changing maximal current or inactivation kinetics. This effect was absent on collagen. Swainsonine and kifunensine reduced mature Piezo1 glycosylation and lowered the mechanical activation threshold. Hypoglycosylation enhanced Ca2+ entry during submaximal stretch in HEK293 cells. In cortical neurons, inhibition of glycan maturation increased somatic Piezo1 immunoreactivity without changing its association with synaptic markers, and potentiated Ca2+ responses to both the Piezo1 activator Yoda1 and submaximal stretch. Thus, mature N-glycans and the extracellular adhesive environment jointly set Piezo1’s mechanical activation threshold rather than merely regulating biosynthesis and trafficking. These findings establish glycosylation-mechanics coupling as a determinant of neuronal force sensing and suggest that, by facilitating Piezo1 recruitment, defective glycosylation may increase cortical vulnerability to mechanical stress, potentially contributing to head trauma-triggered neurological episodes in phosphomannomutase 2 deficiency (PMM2-CDG). Key points Piezo1 channels convert mechanical forces into electrical and calcium signals. N-linked glycans support channel trafficking to the plasma membrane, but whether they tune the force needed for Piezo1 activation was unknown. Mutating either of two conserved N-glycosylation sites in Piezo1 cap domain, or pharmacologically restricting N-glycan maturation, lowered channel’s mechanical activation threshold without changing maximal current or inactivation. This sensitisation depended on the adhesive substrate (occurred on poly-L-lysine but not collagen), and was most evident during submaximal stretch, showing that glycosylation and the extracellular mechanical environment jointly determine Piezo1 force sensing. In mouse cortical neurons, impaired N-glycan maturation increased somatic Piezo1 abundance and enhanced Ca2+ responses to its chemical activator Yoda1 and stretch, without changing synaptic localisation. By allowing weak mechanical inputs to recruit Piezo1 more effectively, defective glycosylation may increase cortical responses to mechanical stress and help explain susceptibility to head trauma-triggered neurological episodes in phosphomannomutase 2 deficiency (PMM2-CDG).

Verification of the expression of Piezo1 and Piezo2 ion channels in the mouse lens during the embryonic, postnatal and adult growth.

It has been proposed that in the absence of a blood supply and any direct innervation, the lens utilizes a variety of mechanosensitive ion channels to transduce changes to its internal and external environments into the activation of signaling pathways that alter fiber cell structure and hence overall lens function. One such mechanosensitive channel is Piezo1, the activation of which has been shown to phosphorylate Myosin light chain kinase (MLCK) and increase the expression of Transglutaminase 2 in fiber cells. To complement these functional studies, we have conducted a comprehensive mapping of the distribution of Piezo1 and Piezo2, the other member of this protein family, throughout all regions of the mouse lens. Using Western blotting, we first show that in addition to Piezo1, the mouse lens also expresses Piezo2. Using immunohistochemistry, we then show that both proteins are present throughout all regions of the lens, but are more concentrated in a discrete zone of high intensity labelling in mature fiber cells in the inner cortical region of the adult mouse lens. Despite being localized to the same localized ring the two proteins exhibited distinctly different subcellular distributions. In the outer cortex Piezo1 was more localized to the membrane, while Piezo2 was predominantly located in the cytoplasm of differentiating fiber cells. To determine at what stage of development this prominent ring of Piezo1/2 labelling was formed, immunohistochemistry was performed at different stages of embryonic and postnatal development. We found Piezo1 and Piezo2 to be both first expressed in the lens vesicle at E10, with both proteins exhibiting a constant level of cytoplasmic labelling across the whole lens throughout embryonic development and up to P6. This pattern of localisation changed from cytoplasmic to membranous at around P15 when the tunica vasculosa lentis was almost fully regressed and eye opening occurred. Our findings suggest that Piezo1/2 recruitment to the plasma membrane is developmentally regulated and associated with a key transitional stage of lens fiber cell maturation.

A TMEM63B variant with enhanced mechanosensitive channel activity and acquired lipid scramblase function.

The neuropathy-causing GARS1ΔETAQ mutation drives pathology in subsets of motor and sensory neurons in mice

Charcot-Marie-Tooth disease type 2D (CMT2D) results from gain-of-function mutations in GARS1, which encodes glycyl-tRNA synthetase (GlyRS), the enzyme responsible for charging transfer RNA (tRNA) with glycine. There are several CMT2D mouse models, but GarsΔETAQ/+ is the only one that bears a patient-sourced mutation. Created using CRISPR/Cas9 to model a 12-nucleotide de novo GARS1 deletion identified in an unusually severe CMT2D patient, GarsΔETAQ/+ mice have previously been shown to display several neuromuscular phenotypes; motor axon loss, denervated neuromuscular junctions (NMJs) and reduced muscle function. Here, we extend these analyses to provide a more comprehensive understanding of both motor and sensory nerve deficits across hind- and fore-limbs. At 3 months, GarsΔETAQ/+ mice possess sex-independent alterations in the levels of neuropathy biomarkers – including decreased NfL and increased periaxin – alongside reduced muscle endurance and strength, and impairments in the sensory modalities of mechanosensation, proprioception and nociception. Underpinning these dysfunctions, we identified site-specific defects comprising altered sensory neuron populations, muscle spindle loss, reduced motor neuron size, disrupted NMJ innervation and maturation, and reduced axonal transport of signalling endosomes in vivo. Together, these experiments show that GarsΔETAQ/+ mice display robust and selective peripheral nerve pathology that manifests in a general distal-to-proximal fashion, priming this CMT2D allele for testing treatments and evaluating mechanisms underlying peripheral nerve vulnerability.