Channels (Austin, Tex.)最新文献

SCN3A, the gene encoding the voltage-gated sodium channel, Nav1.3, plays a critical role in early neuronal development. Although traditionally considered a neonatal channel, emerging evidence has linked SCN3A mutations to a spectrum of neurodevelopmental disorders. Here, we report two clinical cases involving rare SCN3A variants: one with a de novo p.L209P mutation and another with compound heterozygous p.N52H and p.E1809K variants. Whole-exome sequencing and clinical phenotyping revealed overlapping features of global developmental delay, hypotonia, structural brain abnormalities, and, in one case, epilepsy and dystonia. To evaluate their functional impact, we expressed each mutant independently in CHO cells co-transfected with β1 subunits and performed whole-cell patch-clamp electrophysiology. p.N52H reduced current density and hyperpolarized activation, suggesting mixed gain- and loss-of-function effects. p.L209P selectively hyperpolarized the activation curve, while p.E1809K altered fast inactivation and accelerated recovery kinetics. These findings demonstrate that SCN3A variants can disrupt excitability through diverse biophysical mechanisms. Our study expands the clinical and functional landscape of SCN3A-related disorders and underscores the importance of variant-level characterization to guide diagnosis and future therapeutic strategies.

In the retina, Ca²⁺ influx through Ca_v1.4 Ca²⁺ channels triggers neurotransmitter release from rod and cone photoreceptors. Changes in extracellular pH modify channel opening, enabling a feedback regulation of photoreceptor output that contributes to the encoding of color and contrast. However, the mechanisms underlying pH-dependent modulation of Ca_v1.4 are poorly understood. Here, we investigated the role of the C-terminal domain (CTD) of Ca_v1.4 in pH-dependent modulation of Ba²⁺ currents (I_Ba) in HEK293T cells transfected with the full length Ca_V1.4 (FL) or variants lacking portions of the CTD due to alternative splicing (Δe47) or a disease-causing mutation (K1591X). While extracellular alkalinization caused an increase in I_Ba for each variant, the magnitude of this increase was significantly diminished (~40-50%) for both CTD variants; K1591X was unique in showing no pH-dependent increase in maximal conductance. Moreover, the auxiliary α₂δ-4 subunit augmented the pH sensitivity of I_Ba, as compared to α₂δ-1 or no α₂δ, for FL and K1591X but not Δe47. We conclude that the CTD and α₂δ-4 are critical determinants of pH-dependent modulation of Ca_v1.4 and may influence the processing of visual information in normal and diseased states of the retina.

Cellular mechanotransduction refers to the process through which cells perceive mechanical stimuli and subsequently translate them into biochemical signals. Key mechanosensitive ion channels encompass PIEZO, TREK-1, and TRESK. These mechanosensitive ion channels are crucial in regulating specific pathophysiological conditions, including fibrosis, tumor progression, and cellular proliferation and differentiation. Recent research indicates that PIEZO, TREK-1, and TRESK are significant contributors to various types of cancer pain by sensing mechanical stimuli, which subsequently activate internal signaling pathways. Here concentrates on advancements in research concerning PIEZO, TREK-1, and TRESK in cancer pain research, aiming to lay the groundwork for creating new therapeutic drugs that address mechanosensitive ion channels for treating cancer pain.

Fibrosis is usually the final pathological state of many chronic inflammatory diseases and may lead to organ malfunction. Excessive deposition of extracellular matrix (ECM) molecules is a characteristic of most fibrotic tissues. The blood vessel wall contains three layers of membrane structure, including the intima, which is composed of endothelial cells; the media, which is composed of smooth muscle cells; and the adventitia, which is formed by the interaction of connective tissue and fibroblasts. The occurrence and progression of vascular remodeling are closely associated with cardiovascular diseases, and vascular remodeling can alter the original structure and function of the blood vessel. Dysregulation of the composition of the extracellular matrix in blood vessels leads to the continuous advancement of vascular stiffening and fibrosis. Vascular fibrosis reaction leads to excessive deposition of the extracellular matrix in the vascular adventitia, reduces vessel compliance, and ultimately alters key aspects of vascular biomechanics. The pathogenesis of fibrosis in the vasculature and strategies for its reversal have become interesting and important challenges. Ion channels are widely expressed in the cardiovascular system; they regulate blood pressure, maintain cardiovascular function homeostasis, and play important roles in ion transport, cell differentiation, proliferation. In blood vessels, different types of ion channels in fibroblasts, smooth muscle cells and endothelial cells may be relevant mediators of the development of fibrosis in organs or tissues. This review discusses the known roles of ion channels in vascular fibrosis remodeling and discusses potential therapeutic targets for regulating remodeling and repair after vascular injury.

The Kir1.1 (ROMK) family of weak inward rectifiers controls K secretion in the renal CCT and K recycling in the renal TALH. A single point mutant of the inward rectifier, F127V-Kir1.1b was used to investigate the K transition between the selectivity filter and the outer mouth of the channel. We hypothesize that normally an aromatic Phe at the external entryway of Kir1.1b facilitates outward K secretion. We tested this by replacing F127-Kir1.1b with a small aliphatic Val. Results indicate that removal of the Phe at 127 suppresses outward currents that normally contribute to K secretion. Results with the F127V mutant could be explained by increased polyamine block and/or a decrease in the avidity of Kir1.1 for K ions near the outer mouth of the channel. The latter is supported by F127V-Kir1.1b having a lower affinity (K_m = 33 mM) for K than wild-type Kir1.1b (K_m = 7 mM) during external K elevation. Conversely, chelation of K with 18-Crown-6 ether reduced K conductance faster in F127V (half-time = 6s) than in wt-Kir1.1b (half-time = 120s), implying that F127V is less hospitable to external K. In other experiments, positive membrane potentials gated the F127V mutant channel closed at physiological levels of external Ca, possibly by electrostatically depleting K adjacent to the membrane, suggesting that the Phe residue is critical for outward K secretion at physiological Ca. We speculate that the avidity of wt-Kir1.1b for external K could result from a cation-Pi interaction between K and the aromatic F127.

Voltage-gated sodium (Na_v) channels govern membrane excitability by initiating and propagating action potentials. Consistent with their physiological significance, dysfunction, or mutations in these channels are associated with various channelopathies. Na_v channels are thereby major targets for various clinical and investigational drugs. In addition, a large number of natural toxins, both small molecules and peptides, can bind to Na_v channels and modulate their functions. Technological breakthrough in cryo-electron microscopy (cryo-EM) has enabled the determination of high-resolution structures of eukaryotic and eventually human Na_v channels, alone or in complex with auxiliary subunits, toxins, and drugs. These studies have not only advanced our comprehension of channel architecture and working mechanisms but also afforded unprecedented clarity to the molecular basis for the binding and mechanism of action (MOA) of prototypical drugs and toxins. In this review, we will provide an overview of the recent advances in structural pharmacology of Na_v channels, encompassing the structural map for ligand binding on Na_v channels. These findings have established a vital groundwork for future drug development.

The endogenous endocannabinoid-like compound N-arachidonoyl-L-serine (ARA-S) facilitates activation of the human Kv7.1/KCNE1 channel and shortens a prolonged action potential duration and QT interval in guinea pig hearts. Hence, ARA-S is interesting to study further in cardiac models to explore the functional impact of such Kv7.1/KCNE1-mediated effects. To guide which animal models would be suitable for assessing ARA-S effects, and to aid interpretation of findings in different experimental models, it is useful to know whether Kv7.1/KCNE1 channels from relevant species respond similarly to ARA-S. To this end, we used the two-electrode voltage clamp technique to compare the effects of ARA-S on Kv7.1/KCNE1 channels from guinea pig, rabbit, and human Kv7.1/KCNE1, when expressed in Xenopus laevis oocytes. We found that the activation of Kv7.1/KCNE1 channels from all tested species was facilitated by ARA-S, seen as a concentration-dependent shift in the voltage-dependence of channel opening and increase in current amplitude and conductance over a broad voltage range. The rabbit channel displayed quantitatively similar effects as the human channel, whereas the guinea pig channel responded with more prominent increase in current amplitude and maximal conductance. This study suggests that rabbit and guinea pig models are both suitable for studying ARA-S effects mediated via Kv7.1/KCNE1.

Variants in KCNMA1, encoding the voltage- and calcium-activated K⁺ (BK) channel, are associated with human neurological disease. The effects of gain-of-function (GOF) and loss-of-function (LOF) variants have been predominantly studied on BK channel currents evoked under steady-state voltage and Ca²⁺ conditions. However, in their physiological context, BK channels exist in partnership with voltage-gated Ca²⁺ channels and respond to dynamic changes in intracellular Ca²⁺ (Ca²⁺_i). In this study, an L-type voltage-gated Ca²⁺ channel present in the brain, Ca_V1.2, was co-expressed with wild type and mutant BK channels containing GOF (D434G, N999S) and LOF (H444Q, D965V) patient-associated variants in HEK-293T cells. Whole-cell BK currents were recorded under Ca_V1.2 activation using buffering conditions that restrict Ca²⁺_i to nano- or micro-domains. Both conditions permitted wild type BK current activation in response to Ca_V1.2 Ca²⁺ influx, but differences in behavior between wild type and mutant BK channels were reduced compared to prior studies in clamped Ca²⁺_i. Only the N999S mutation produced an increase in BK current in both micro- and nano-domains using square voltage commands and was also detectable in BK current evoked by a neuronal action potential within a microdomain. These data corroborate the GOF effect of N999S on BK channel activity under dynamic voltage and Ca²⁺ stimuli, consistent with its pathogenicity in neurological disease. However, the patient-associated mutations D434G, H444Q, and D965V did not exhibit significant effects on BK current under Ca_V1.2-mediated Ca²⁺ influx, in contrast with prior steady-state protocols. These results demonstrate a differential potential for KCNMA1 variant pathogenicity compared under diverse voltage and Ca²⁺ conditions.

The transient receptor potential melastatin 7 channel (TRPM7) is a nonselective cation channel highly expressed in some human cancer tissues. TRPM7 is involved in the proliferation, migration, invasion, and epithelial-mesenchymal transition (EMT) of cancer cells. Modulation of TRPM7 could be a promising therapeutic strategy for treating cancer; however, efficient and selective pharmacological TRPM7 modulators are lacking. In this study we investigated N- [4- (4, 6-dimethyl- 2-pyrimidinyloxy) - 3- methylphenyl] -N' - [2 -(dimethylamino)] benzoylurea (SUD), a newly synthesized benzoylurea derivative, for its effects on cancer cell migration and EMT and on functional expression of TRPM7. Our previous studies showed that SUD induces cell cycle arrest and apoptosis of MCF-7 and BGC-823 cells (human breast cancer and gastric cancer cell lines, respectively). Here, we show that SUD significantly decreased the migration of both types of cancer cells. Moreover, SUD decreased vimentin expression and increased E-cadherin expression in both cell types, indicating that EMT is also decreased by SUD. Importantly, SUD potentially reduced the TRPM7-like current in a concentration-dependent manner and decreased TRPM7 expression through the PI3K/Akt signaling pathway. Finally, molecular docking simulations were used to investigate potential SUD binding sites on TRPM7. In summary, our research demonstrated that SUD is an effective TRPM7 inhibitor and a potential agent to suppress the metastasis of breast and gastric cancer by inhibiting TRPM7 expression and function.

Alterations in ion channel expression and function known as "electrical remodeling" contribute to the development of hypertrophy and to the emergence of arrhythmias and sudden cardiac death. However, comparing current density values - an electrophysiological parameter commonly utilized to assess ion channel function - between normal and hypertrophied cells may be flawed when current amplitude does not scale with cell size. Even more, common routines to study equally sized cells or to discard measurements when large currents do not allow proper voltage-clamp control may introduce a selection bias and thereby confound direct comparison. To test a possible dependence of current density on cell size and shape, we employed whole-cell patch-clamp recording of voltage-gated sodium and calcium currents in Langendorff-isolated ventricular cardiomyocytes and Purkinje myocytes, as well as in cardiomyocytes derived from trans-aortic constriction operated mice. Here, we describe a distinct inverse relationship between voltage-gated sodium and calcium current densities and cell capacitance both in normal and hypertrophied cells. This inverse relationship was well fit by an exponential function and may be due to physiological adaptations that do not scale proportionally with cell size or may be explained by a selection bias. Our study emphasizes the need to consider cell size bias when comparing current densities in cardiomyocytes of different sizes, particularly in hypertrophic cells. Conventional comparisons based solely on mean current density may be inadequate for groups with unequal cell size or non-proportional current amplitude and cell size scaling.