Selective Chemical Activation of Piezo1 in Leukemia Cell Membrane: Single Channel Analysis

Functional characterization of native Piezo1 as calcium and magnesium influx pathway in human myeloid leukemia cells

Piezo1 is a Ca2+-permeable mechanically activated ion channel that is involved in various physiological processes and cellular responses to mechanical stimuli. The study of biophysical characteristics of Piezo1 is important for understanding the mechanisms of its function and regulation. Stretch activation, a routine approach that is applied to stimulate Piezo1 activity in the plasma membrane, has a number of significant limitations that complicate precise single-channel analysis. Here, we aimed to determine pore properties of native Piezo1, specifically to examine permeation for physiologically relevant signaling divalent ions (calcium and magnesium) in human myeloid leukemia K562 cells using Piezo1-specific chemical agonist, Yoda1. Using a combination of low-noise single-current patch-clamp recordings of Piezo1 activity in response to Yoda1, we have determined single-channel characteristics of native Piezo1 under various ionic conditions. Whole-cell assay allowed us to directly measure Piezo1 single currents carried by Ca2+ or Mg2+ ions in the absence of other permeable cations in the extracellular solutions; unitary conductance values estimated at various concentrations of Mg2+ revealed strong saturation effect. Patch clamp data complemented with fluorescent imaging clearly evidenced Ca2+ and Mg2+ entry via native Piezo1 channel in human leukemia K562 cells. Mg2+ influx via Piezo1 was detected under quasi-physiological conditions, thus showing that Piezo1 channels could potentially provide the physiological relevant pathway for Mg2+ ion transport and contribute to the regulation of Mg2+-dependent intracellular signaling.

Microglial Piezo1 mechanosensitive channel as a therapeutic target in Alzheimer's disease

Microglia are the resident macrophages of the central nervous system (CNS) that control brain development, maintain neural environments, respond to injuries, and regulate neuroinflammation. Despite their significant impact on various physiological and pathological processes across mammalian biology, there remains a notable gap in our understanding of how microglia perceive and transmit mechanical signals in both normal and diseased states. Recent studies have revealed that microglia possess the ability to detect changes in the mechanical properties of their environment, such as alterations in stiffness or pressure. These changes may occur during development, aging, or in pathological conditions such as trauma or neurodegenerative diseases. This review will discuss microglial Piezo1 mechanosensitive channels as potential therapeutic targets for Alzheimer's disease (AD). The structure, function, and modulation of Piezo1 will be discussed, as well as its role in facilitating microglial clearance of misfolded amyloid-β (Aβ) proteins implicated in the pathology of AD.

Capsazepine activates amiloride-insensitive ENaC-like channels in human leukemia cells

Sodium influx carried out by ion channels is one of the main regulators of water-salt and volume balance in cells of blood origin. Previously, we described amiloride-insensitive ENaC-like channels in human myeloid leukemia K562 cells; the intracellular regulatory mechanisms of the channels are associated with actin cytoskeleton dynamics. Recently, an extracellular mechanism of ENaC-like channels activation in K562 cells by the action of serine protease trypsin has been revealed. The other extracellular pathways that modulate ENaC (epithelial Na+ channel) activity and sodium permeability in transformed blood cells are not yet fully investigated. Here, we study the action of capsazepine (CPZ), as δ-ENaC activator, on single channel activity in K562 cells in whole-cell patch clamp experiments. Addition of CPZ (2 μM) to the extracellular solution caused an activation of sodium channels with typical features; unitary conductance was 15.1 ± 0.8 pS. Amiloride derivative benzamil (50 μM) did not inhibit their activity. Unitary currents and conductance of CPZ-activated channels were higher in Na+-containing extracellular solution than in Li+, that is one of the main fingerprints of δ-ENaC. The results of RT-PCR analysis and immunofluorescence staining also confirmed the expression of δ-hENaC (as well as α-, β-, γ-ENaC) at the mRNA and protein level. These findings allow us to speculate that CPZ activates amiloride-insensitive ENaC-like channels that contain δ-ENaC in К562 cells. Our data reveal a novel extracellular mechanism for ENaC-like activation in human leukemia cells.

Piezo1 Activation Prevents Spheroid Formation by Malignant Melanoma SK-MEL-2 Cells

Melanoma is a highly aggressive type of skin cancer produced through the malignant transformation of melanocytes, and it is usually associated with a poor prognosis. Clinically, melanoma has several stages associated with migration and invasion of the cells through the skin's layers, the rapid spreading of cells and the formation of tumors in multiple organs. The main problem is the emergence of resistance in melanoma to the applied methods of treatment; thus, it is of primary importance to find more crucial signaling pathways that control the progression of this type of cancer and could be targeted to prevent melanoma spreading. Here, we uncover novel aspects of the role of the mechanosensitive ion channel Piezo1 in melanoma tumor formation. Using a combinative approach, we showed the functional expression of mechanosensitive Piezo1 channels in the aggressive human melanoma SK-MEL-2 cell line. We found that chemical activation of Piezo1 by its agonist, Yoda1, prevents melanoma spheroid formation; thus, Piezo1 could be a potential target for selective modulation aimed at the prevention of melanoma development.

Mechanosensitive Ion Channels and Their Role in Cancer Cells

Mechanical forces are an inherent element in the world around us. The effects of their action can be observed both on the macro and molecular levels. They can also play a prominent role in the tissues and cells of animals due to the presence of mechanosensitive ion channels (MIChs) such as the Piezo and TRP families. They are essential in many physiological processes in the human body. However, their role in pathology has also been observed. Recent discoveries have highlighted the relationship between these channels and the development of malignant tumors. Multiple studies have shown that MIChs mediate the proliferation, migration, and invasion of various cancer cells via various mechanisms. This could show MIChs as new potential biomarkers in cancer detection and prognosis and interesting therapeutic targets in modern oncology. Our paper is a review of the latest literature on the role of the Piezo1 and TRP families in the molecular mechanisms of carcinogenesis in different types of cancer.

Piezo1 Affects Temporomandibular Joint Osteoarthritis by Influencing pSmad3

Objective: The aim of this research was to study the expression of Piezo1 in a rat temporomandibular joint osteoarthritis animal model and to explore its mechanism for inducing inflammatory changes. Methods: A total of 24male SD rats aged approximately 8 weeks were randomly divided into three groups: the blank control group, complete Freund's adjuvant group (CFA), and CFA + inhibitor (GsMTx4) group. After 3 weeks, the condylar heads of the rats were evaluated by micro-CT, HE, immunohistochemistry, safranin O staining, and other experimental techniques. Protein was extracted from the subchondral bone, and the changes in Piezo1, Smad3, and pSmad3 levels in each group were detected by Western blotting. p < 0.05 was considered to indicate statistical significance. Results: The degree of damage to the cartilage and subchondral bone in the Piezo1 inhibitor group was smaller than that in the CFA group. The expression level of Piezo1 in the CFA group was higher than that in the other groups, and the difference was statistically significant. The expression of pSmad3 in the CFA group was also higher than that in the other groups (p < 0.05). Conclusion: Piezo1 is expressed in the condylar cartilage and subchondral bone of rats, and the degree of condylar destruction can be improved by influencing the pSmad3 expression.

Store-Operated Ca2+ Entry Contributes to Piezo1-Induced Ca2+ Increase in Human Endometrial Stem Cells

Endometrial mesenchymal stem cells (eMSCs) are a specific class of stromal cells which have the capability to migrate, develop and differentiate into different types of cells such as adipocytes, osteocytes or chondrocytes. It is this unique plasticity that makes the eMSCs significant for cellular therapy and regenerative medicine. Stem cells choose their way of development by analyzing the extracellular and intracellular signals generated by a mechanical force from the microenvironment. Mechanosensitive channels are part of the cellular toolkit that feels the mechanical environment and can transduce mechanical stimuli to intracellular signaling pathways. Here, we identify previously recorded, mechanosensitive (MS), stretch-activated channels as Piezo1 proteins in the plasma membrane of eMSCs. Piezo1 activity triggered by the channel agonist Yoda1 elicits influx of Ca²⁺, a known modulator of cytoskeleton reorganization and cell motility. We found that store-operated Ca²⁺ entry (SOCE) formed by Ca²⁺-selective channel ORAI1 and Ca²⁺ sensors STIM1/STIM2 contributes to Piezo1-induced Ca²⁺ influx in eMSCs. Particularly, the Yoda1-induced increase in intracellular Ca²⁺ ([Ca²⁺]_i) is partially abolished by 2-APB, a well-known inhibitor of SOCE. Flow cytometry analysis and wound healing assay showed that long-term activation of Piezo1 or SOCE does not have a cytotoxic effect on eMSCs but suppresses their migratory capacity and the rate of cell proliferation. We propose that the Piezo1 and SOCE are both important determinants in [Ca²⁺]_i regulation, which critically affects the migratory activity of eMSCs and, therefore, could influence the regenerative potential of these cells.

Deregulated calcium signaling in blood cancer: Underlying mechanisms and therapeutic potential

Intracellular calcium signaling regulates diverse physiological and pathological processes. In solid tumors, changes to calcium channels and effectors via mutations or changes in expression affect all cancer hallmarks. Such changes often disrupt transport of calcium ions (Ca²⁺) in the endoplasmic reticulum (ER) or mitochondria, impacting apoptosis. Evidence rapidly accumulates that this is similar in blood cancer. Principles of intracellular Ca²⁺ signaling are outlined in the introduction. We describe different Ca²⁺-toolkit components and summarize the unique relationship between extracellular Ca²⁺ in the endosteal niche and hematopoietic stem cells. The foundational data on Ca²⁺ homeostasis in red blood cells is discussed, with the demonstration of changes in red blood cell disorders. This leads to the role of Ca²⁺ in neoplastic erythropoiesis. Then we expand onto the neoplastic impact of deregulated plasma membrane Ca²⁺ channels, ER Ca²⁺ channels, Ca²⁺ pumps and exchangers, as well as Ca²⁺ sensor and effector proteins across all types of hematologic neoplasms. This includes an overview of genetic variants in the Ca²⁺-toolkit encoding genes in lymphoid and myeloid cancers as recorded in publically available cancer databases. The data we compiled demonstrate that multiple Ca²⁺ homeostatic mechanisms and Ca²⁺ responsive pathways are altered in hematologic cancers. Some of these alterations may have genetic basis but this requires further investigation. Most changes in the Ca²⁺-toolkit do not appear to define/associate with specific disease entities but may influence disease grade, prognosis, treatment response, and certain complications. Further elucidation of the underlying mechanisms may lead to novel treatments, with the aim to tailor drugs to different patterns of deregulation. To our knowledge this is the first review of its type in the published literature. We hope that the evidence we compiled increases awareness of the calcium signaling deregulation in hematologic neoplasms and triggers more clinical studies to help advance this field.