Current topics in membranes最新文献

"No cell could exist without ion channels" (Clay Armstrong; 1999). Since the discovery in the early 1950s, that ions move across biological membranes, the idea that changes of ionic gradients can generate biological signals has fascinated scientists in any fields. Soon later (1960s) it was found that ionic flows were controlled by a class of specific and selective proteins called ion channels. Thus, it became clear that the concerted activities of these proteins can initiate, arrest, and finely tune a variety of biochemical cascades which offered the opportunity to better understand both biology and pathology. Cancer is a disease that is notoriously difficult to treat due its heterogeneous nature which makes it the deadliest disease in the developed world. Recently, emerging evidence has established that potassium channels are critical modulators of several hallmarks of cancer including tumor growth, metastasis, and metabolism. Nevertheless, the role of potassium ion channels in cancer biology and the therapeutic potential offered by targeting these proteins has not been explored thoroughly. This chapter is addressed to both cancer biologists and ion channels scientists and it aims to shine a light on the established and potential roles of potassium ion channels in cancer biology and on the therapeutic benefit of targeting potassium channels with activator molecules.

Chloride intracellular channel 1 (CLIC1) has emerged as a therapeutic target in various cancers. CLIC1 promotes cell cycle progression and cancer stem cell (CSC) self-renewal. Furthermore, CLIC1 is shown to play diverse roles in proliferation, cell volume regulation, tumour invasion, migration, and angiogenesis. In glioblastoma (GB), CLIC1 facilitates the G1/S phase transition and tightly regulates glioma stem-like cells (GSCs), a rare population of self-renewing CSCs with central roles in tumour resistance to therapy and tumour recurrence. CLIC1 is found as either a monomeric soluble protein or as a non-covalent dimeric protein that can form an ion channel. The ratio of dimeric to monomeric protein is altered in GSCs and depends on the cell redox state. Elucidating the mechanisms underlying the alterations in CLIC1 expression and structural transitions will further our understanding of its role in GSC biology. This review will highlight the role of CLIC1 in GSCs and its significance in facilitating different hallmarks of cancer.

The endothelial glycocalyx is an extracellular matrix that coats the endothelium and extends into the lumen of blood vessels, acting as a barrier between the vascular wall and blood flowing through the vessel. This positioning of the glycocalyx permits a variety of its constituents, including the major endothelial proteoglycans glypican-1 and syndecan-1, as well as the major glycosaminoglycans heparan sulfate and hyaluronic acid, to contribute to the processes of mechanosensation and subsequent mechanotransduction following such stimuli as elevated shear stress. To coordinate the vast array of processes that occur in response to physical force, the glycocalyx interacts with a plethora of membrane and cytoskeletal proteins to carry out specific signaling pathways resulting in a variety of responses of endothelial cells and, ultimately, blood vessels to mechanical force. This review focuses on proposed glycocalyx-protein relationships whereby the endothelial glycocalyx interacts with a variety of membrane and cytoskeletal proteins to transduce force into a myriad of chemical signaling pathways. The established and proposed interactions at the molecular level are discussed in context of how the glycocalyx regulates membrane/cytoskeletal protein function in the many processes of endothelial mechanotransduction.

The endothelial glycocalyx is a dynamic surface layer composed of proteoglycans, glycoproteins, and glycosaminoglycans with a key role in maintaining endothelial cell homeostasis. Its functions include the regulation of endothelial barrier permeability and stability, the transduction of mechanical forces from the vascular lumen to the vessel walls, serving as a binding site to multiple growth factors and vasoactive agents, and mediating the binding of platelets and the migration of leukocytes during an inflammatory response. Many of these processes are associated with changes in intracellular calcium levels that may occur through mechanisms that alter calcium entry in the endothelium or the release of calcium from the endoplasmic reticulum. Whether the endothelial glycocalyx can regulate calcium dynamics in endothelial cells is unresolved. Interestingly, during cardiovascular disease progression, changes in calcium dynamics are observed in association with the degradation of the glycocalyx and with changes in barrier permeability and vascular reactivity. Herein, we aim to provide a summarized overview of what is known regarding the role of the glycocalyx as a regulator of endothelial barrier and vascular reactivity during homeostatic and pathological conditions and to provide a perspective on how such processes may relate to calcium dynamics in endothelial cells, exploring a possible connection between components of the glycocalyx and calcium-sensitive pathways in the endothelium.

Cancer and neurodegenerative disease, albeit fundamental differences, share some common pathogenic mechanisms. Accordingly, both conditions are associated with aberrant cell proliferation and migration. Here, we review the causative role played by potassium (K⁺) channels, a fundamental class of proteins, in cancer and neurodegenerative disease. The concept that emerges from the review of the literature is that K⁺ channels can promote the development and progression of cancerous and neurodegenerative pathologies by dysregulating cell proliferation and migration. K⁺ channels appear to control these cellular functions in ways that not necessarily depend on their conducting properties and that involve the ability to directly or indirectly engage growth and survival signaling pathways. As cancer and neurodegenerative disease represent global health concerns, identifying commonalities may help understand the molecular basis for those devastating conditions and may facilitate the design of new drugs or the repurposing of existing drugs.

The cytoplasmic Ca²⁺ concentration and the activity of K⁺ channels on the plasma membrane regulate cellular processes ranging from mitosis to oriented migration. The interplay between Ca²⁺ and K⁺ signals is intricate, and different cell types rely on peculiar cellular mechanisms. Derangement of these mechanisms accompanies the neoplastic progression. The calcium signals modulated by voltage-gated (K_V) and calcium-dependent (K_Ca) K⁺ channel activity regulate progression of the cell division cycle, the release of growth factors, apoptosis, cell motility and migration. Moreover, K_V channels regulate the cell response to the local microenvironment by assembling with cell adhesion and growth factor receptors. This chapter summarizes the pathophysiological roles of Ca²⁺ and K⁺ fluxes in normal and cancer cells, by concentrating on several biological systems in which these functions have been studied in depth, such as early embryos, mammalian cell lines, T lymphocytes, gliomas and colorectal cancer cells. A full understanding of the underlying mechanisms will offer a comprehensive view of the ion channel implication in cancer biology and suggest potential pharmacological targets for novel therapeutic approaches in oncology.

All cells in the human body are covered by a complex meshwork of sugars as well as proteins and lipids to which these sugars are attached, collectively termed the glycocalyx. Over the past few decades, the glycocalyx has been implicated in a range of vital cellular processes in health and disease. Therefore, it has attracted considerable interest as a therapeutic target. Considering its omnipresence and its relevance for various areas of cell biology, the glycocalyx should be a versatile platform for therapeutic intervention, however, the full potential of the glycocalyx as therapeutic target is yet to unfold. This might be attributable to the fact that glycocalyx alterations are currently discussed mainly in the context of specific diseases. In this perspective review, we shift the attention away from a disease-centered view of the glycocalyx, focusing on changes in glycocalyx state. Furthermore, we survey important glycocalyx-targeted drugs currently available and finally discuss future steps. We hope that this approach will inspire a unified, holistic view of the glycocalyx in disease, helping to stimulate novel glycocalyx-targeted therapy strategies.

Voltage-gated sodium channels (Na_v) are protein complexes that play fundamental roles in the transmission of signals in the nervous system, at the neuromuscular junction and in the heart. They are mainly present in excitable cells where they are responsible for triggering action potentials. Dysfunctions in Na_v ion conduction give rise to a wide range of conditions, including neurological disorders, hypertension, arrhythmia, pain and cancer. Na_v family 1 is composed of nine members, named numerically from 1 to 9. A Nax family also exists and is involved in body-fluid homeostasis. Of particular interest is Na_v1.7 which is highly expressed in the sensory neurons of the dorsal root ganglions, where it is involved in the propagation of pain sensation. Gain-of-function mutations in Na_v1.7 cause pathologies associated with increased pain sensitivity, while loss-of-function mutations cause reduced sensitivity to pain. The last decade has seen considerable effort in developing highly specific Na_v1.7 blockers as pain medications, nonetheless, sufficient efficacy has yet to be achieved. Evidence is now conclusively showing that Na_vs are also present in many types of cancer cells, where they are involved in cell migration and invasiveness. Na_v1.7 is anomalously expressed in endometrial, ovarian and lung cancers. Na_v1.7 is also involved in Chemotherapy Induced Peripheral Neuropathy (CIPN). We propose that the knowledge and tools developed to study the role of Na_v1.7 in pain can be exploited to develop novel cancer therapies. In this chapter, we illustrate the various aspects of Na_v1.7 function in pain, cancer and CIPN, and outline therapeutic approaches.

Kidneys are central for whole body water and electrolyte balance by first filtering plasma at the glomeruli and then processing the filtrate along the renal nephron until the final urine is produced. Renal nephron epithelial cells mediate transport of water and solutes which is under the control of systemic hormones as well as local mechanical stimuli arising from alterations in fluid flow. TRPV4 is a mechanosensitive Ca²⁺ channel abundantly expressed in different segments of the renal nephron. The accumulated evidence suggests a critical role for TRPV4 in sensing variations in flow rates. In turn, TRPV4 activation triggers numerous downstream cellular responses stimulated by elevated intracellular Ca²⁺ concentrations [Ca²⁺]_i. In this review, we discuss the recent concepts in flow-mediated regulation of solute homeostasis by TRPV4 in different segments of renal nephron. Specifically, we summarize the evidence for TRPV4 involvement in endocytosis-mediated albumin uptake in the proximal tubule, reactive oxygen species (ROS) generation in the ascending loop of Henle, and maintaining K⁺ homeostasis in the connecting tubule/collecting duct. Finally, we outline the function and significance of TRPV4 in the setting of polycystic kidney disease.

Transient receptor potential vanilloid sub-type 4 (TRPV4) is a six transmembrane protein that acts as a non-selective Ca²⁺ channel. Notably, TRPV4 is present in almost all animals, from lower eukaryotes to humans and is expressed in diverse tissue and cell types. Accordingly, TRPV4 is endogenously expressed in several types of immune cells that represent both innate and adaptive immune systems of higher organism. TRPV4 is known to be activated by physiological temperature, suggesting that it acts as a molecular temperature sensor and thus plays a key role in temperature-dependent immune activation. It is also activated by diverse endogenous ligands, lipid metabolites, physical and mechanical stimuli. Both expression and function of TRPV4 in various immune cells, including T cells and macrophages, are also modulated by multiple pro- and anti-inflammatory compounds. The results from several laboratories suggest that TRPV4 is involved in the immune activation, a phenomenon with evolutionary significance. Because of its diverse engagement in the neuronal and immune systems, TRPV4 is a potential therapeutic target for several immune-related disorders.