Homocysteine is a non-proteinogenic amino acid formed during the metabolism of methionine to cysteine and plays a critical role in maintaining cellular homeostasis. Although multiple enzymatic pathways tightly regulate homocysteine levels, their dysfunction can lead to elevated circulating homocysteine, which is recognized as a risk factor for various cardiovascular and neurological disorders. While most evidence linking homocysteine to specific pathologies comes from observational studies, emerging data suggest that dysregulation of ion channels may be an important underlying mechanism. In this review, we summarize the effects of homocysteine on the expression and function of key ion channel families including calcium, sodium, and potassium channels, and discuss their potential pathophysiological implications.

Temperature strongly influences neuronal excitability and voltage-gated ion channel function. Cav3.2 T-type calcium channels are highly expressed in dorsal root ganglion and trigeminal ganglion neurons, where they contribute to nociceptive signaling, cold hypersensitivity, and neuropathic pain. However, how temperature influences Cav3.2 function during repetitive neuronal activity remains incompletely understood. Here, we investigated the effects of temperature on Cav3.2 gating and calcium influx using whole-cell voltage-clamp recordings performed at 37 °C, 22 °C, and 13 °C. Cooling markedly reduced macroscopic current amplitude under conventional voltage-step protocols while profoundly slowing activation, inactivation, deactivation, and recovery from inactivation kinetics. In contrast, steady-state voltage dependence was comparatively less affected, revealing highly non-uniform temperature sensitivity across distinct gating transitions. During trains of action-potential-like waveforms delivered at 10–100 Hz, increasing stimulation frequency progressively inverted the temperature dependence of Cav3.2-mediated calcium influx. Although cooling reduced peak current amplitude, it promoted sustained channel activity and enhanced cumulative calcium influx during high-frequency stimulation. This functional inversion resulted from disproportionate slowing of channel gating kinetics, particularly inactivation and deactivation. A kinetically slowed Cav3.2 variant (V416R) reproduced key low-temperature kinetic features and markedly attenuated this inversion. Together, these findings identify a previously unrecognized temperature-dependent functional inversion of Cav3.2 channels during repetitive activity with potentially important pathophysiological implications.

Mutations in CACNA1C, the gene encoding Cav1.2 voltage-gated calcium channels, are associated with a spectrum of disorders, including Timothy syndrome and other neurodevelopmental and cardiac conditions. In this study, we report a child with a de novo heterozygous missense variant (c.1973T > C; L658P) in CACNA1C, presenting with refractory epilepsy, global developmental delay, hypotonia, and multiple systemic abnormalities, but without overt cardiac dysfunction. Electrophysiological analysis of the recombinant Cav1.2 L658P variant revealed profound gating alterations, most notably a significant hyperpolarizing shift in the voltage dependence of activation and inactivation. Additionally, molecular modeling suggested that the L658P mutation disrupts interactions within the IIS5 transmembrane segment, reducing the energy barrier for state transitions and facilitating channel opening at more negative voltages. These findings establish L658P as a pathogenic CACNA1C variant primarily associated with severe neurological dysfunction and expands the phenotypic spectrum of CACNA1C-related disorders.

This study highlights the complementarity of automated patch-clamp (APC) and manual patch-clamp (MPC) approaches to describe the electrophysiological properties of eighteen Cav3.1 calcium channel variants associated with various neurological conditions. Current density was measured efficiently for all variants in APC experiments, with four variants (p.V184G, p.N1200S, p.S1263A and p.D2242N) showing elevated current densities, compared to wild-type Cav3.1 channel, while six variants (p.M197R, p.V392M, p.F956del, p.I962N, p.I1412T, and p.G1534D) displayed reduced current densities, and were therefore preferentially studied using MPC. The electrophysiological properties were well preserved in APC (e.g., inactivation and deactivation kinetics, steady-state properties), with only the APC-MPC correlation for activation kinetics being less robust. In addition, neuronal modeling, using a deep cerebellar neuron (DCN) environment, revealed that most of the variants localized to the intracellular gate (S5 and S6 segments) could increase DCN spike frequencies. This DCN firing was highly dependent on current density and further pointed to the gain-of-function (GOF) properties of p.A961T and p.M1531V, the two recurrent variants associated with Spinocerebellar Ataxia type-42 with Neurodevelopmental Deficit (SCA42ND). Action-potential (AP) clamp experiments performed using cerebellar and thalamic neuron activities further established the GOF properties of p.A961T and p.M1531V variants. Overall, this study demonstrates that APC is well-suited for high-throughput analysis of Cav3.1 channel variants, and that MPC complements APC for characterizing low-expression variants. Furthermore, in silico modeling and AP clamp experiments reveal that the gain- or loss-of-function properties of the variants are determined by how the Cav3.1 channel decodes the electrophysiological context of a neuron.

Induced pluripotent stem cell (iPSC)-derived motor neurons provide a powerful platform for studying motor neuron diseases. These cells enable human-specific modeling of disease mechanisms and high-throughput drug screening. While commercially available iPSC-derived motor neurons offer a convenient alternative to time-intensive differentiation protocols, their electrophysiological properties and maturation require comprehensive evaluation to validate their utility for research and therapeutic applications. In this study, we characterized the electrophysiological properties of commercially available iPSC-derived motor neurons. Immunofluorescence confirmed the expression of motor neuron-specific biomarkers, indicating successful differentiation and maturation. Electrophysiological recordings revealed stable passive membrane properties, maturation-dependent improvements in action potential kinetics, and progressive increases in repetitive firing. Voltage-clamp analyses confirmed the functional expression of key ion channels, including high- and low-voltage-activated calcium channels, TTX-sensitive and TTX-insensitive sodium channels, and voltage-gated potassium channels. While the neurons exhibited hallmark features of motor neuron physiology, high input resistance, depolarized resting membrane potentials, and limited firing capacity suggest incomplete electrical maturation. Altogether, these findings underscore the potential of commercially available iPSC-derived motor neurons as a practical resource for MND research, while highlighting the need for optimized protocols to support prolonged culture and full maturation.

Elevated plasma homocysteine (Hcy) levels lead to hyperhomocysteinemia, a condition associated with various neurological disorders affecting multiple brain regions, including the hippocampus. In this study, we investigated the effects of exposing cultured rat hippocampal neurons to Hcy concentrations corresponding to mild, moderate, and severe hyperhomocysteinemia. A short 24-hour exposure had minimal effects, whereas prolonged exposure up to 14 days moderately enhanced hippocampal excitability without altering the gene expression of voltage-dependent calcium, sodium, or potassium channels or intracellular calcium levels. These findings suggest that Hcy-induced changes in neuronal excitability may contribute to neuropathologies associated with hyperhomocysteinemia.

T-type calcium channelopathies encompass a group of human disorders either caused or exacerbated by mutations in the genes encoding different T-type calcium channels. Recently, a new heterozygous missense mutation in the CACNA1H gene that encodes the Ca v 3.2 T-type calcium channel was reported in a patient presenting with epilepsy and hearing loss—apparently the first CACNA1H mutation to be associated with a sensorineural hearing condition. This mutation leads to the substitution of an arginine at position 132 with a histidine (R132H) in the proximal extracellular end of the second transmembrane helix of Ca v 3.2. In this study, we report the electrophysiological characterization of this new variant using whole-cell patch clamp recordings in tsA-201 cells. Our data reveal minor gating alterations of the channel evidenced by a mild increase of the T-type current density and slower recovery from inactivation, as well as an enhanced sensitivity of the channel to external pH change. To what extend these biophysical changes and pH sensitivity alterations induced by the R132H mutation contribute to the observed pathogenicity remains an open question that will necessitate the analysis of additional CACNA1H variants associated with the same pathologies.

T-type calcium channels perform crucial physiological roles across a wide spectrum of tissues, spanning both neuronal and non-neuronal system. For instance, they serve as pivotal regulators of neuronal excitability, contribute to cardiac pacemaking, and mediate the secretion of hormones. These functions significantly hinge upon the intricate interplay of T-type channels with interacting proteins that modulate their expression and function at the plasma membrane. In this review, we offer a panoramic exploration of the current knowledge surrounding these T-type channel interactors, and spotlight certain aspects of their potential for drug-based therapeutic intervention.

Department of Pathophysiology, Third Faculty of Medicine, Charles University, Prague, Czech Republic Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article.

Missense mutations in the human secretary carrier-associated membrane protein 5 (SCAMP5) cause a variety of neurological disorders including neurodevelopmental delay, epilepsy, and Parkinson's disease. We recently documented the importance of SCAMP2 in the regulation of T-type calcium channel expression in the plasma membrane. Here, we show that similar to SCAMP2, the co-expression of SCAMP5 in tsA-201 cells expressing recombinant Cav3.1, Cav3.2, and Cav3.3 channels nearly abolished whole-cell T-type currents. Recording of intramembrane charge movements revealed that SCAMP5-induced inhibition of T-type currents is primarily caused by the reduced expression of functional channels in the plasma membrane. Moreover, we show that SCAMP5-mediated downregulation of Cav3.2 channels is essentially preserved with disease-causing SCAMP5 R91W and G180W mutations. Hence, this study extends our previous findings with SCAMP2 and indicates that SCAMP5 also contributes to repressing the expression of T-type channels in the plasma membrane.

Amyotrophic lateral sclerosis (ALS) stands as the most prevalent and severe form of motor neuron disease, affecting an estimated 2 in 100,000 individuals worldwide. It is characterized by the progressive loss of cortical, brainstem, and spinal motor neurons, ultimately resulting in muscle weakness and death. Although the etiology of ALS remains poorly understood in most cases, the remodelling of ion channels and alteration in neuronal excitability represent a hallmark of the disease, manifesting not only during the symptomatic period but also in the early pre-symptomatic stages. In this review, we delve into these alterations observed in ALS patients and preclinical disease models, and explore their consequences on neuronal activities. Furthermore, we discuss the potential of ion channels as therapeutic targets in the context of ALS.

Voltage-gated calcium channels are essential regulators of brain function where they support depolarization-induced calcium entry into neurons. They consist of a pore-forming subunit (Cavα1) that requires co-assembly with ancillary subunits to ensure proper functioning of the channel. Among these ancillary subunits, the Cavβ plays an essential role in regulating surface expression and gating of the channels. This regulation requires the direct binding of Cavβ onto Cavα1 and is mediated by the alpha interacting domain (AID) within the Cavα1 subunit and the α binding pocket (ABP) within the Cavβ subunit. However, additional interactions between Cavα1 and Cavβ have been proposed. In this study, we analyzed the importance of Cavβ3 surface charged residues in the regulation of Cav2.1 channels. Using alanine-scanning mutagenesis combined with electrophysiological recordings we identified several amino acids within the Cavβ3 subunit that contribute to the gating of the channel. These findings add to the notion that additional contacts besides the main AID/ABP interaction may occur to fine-tune the expression and properties of the channel.

Trigeminal neuralgia (TN) is a rare form of chronic neuropathic pain characterized by spontaneous or elicited paroxysms of electric shock-like or stabbing pain in a region of the face. While most cases occur in a sporadic manner and are accompanied by intracranial vascular compression of the trigeminal nerve root, alteration of ion channels has emerged as a potential exacerbating factor. Recently, whole exome sequencing analysis of familial TN patients identified 19 rare variants in the gene CACNA1H encoding for Cav3.2T-type calcium channels. An initial analysis of 4 of these variants pointed to a pathogenic role. In this study, we assessed the electrophysiological properties of 13 additional TN-associated Cav3.2 variants expressed in tsA-201 cells. Our data indicate that 6 out of the 13 variants analyzed display alteration of their gating properties as evidenced by a hyperpolarizing shift of their voltage dependence of activation and/or inactivation resulting in an enhanced window current supported by Cav3.2 channels. An additional variant enhanced the recovery from inactivation. Simulation of neuronal electrical membrane potential using a computational model of reticular thalamic neuron suggests that TN-associated Cav3.2 variants could enhance neuronal excitability. Altogether, the present study adds to the notion that ion channel polymorphisms could contribute to the etiology of some cases of TN and further support a role for Cav3.2 channels.

Voltage-gated Na+ (NaV) channels are significant therapeutic targets for the treatment of cardiac and neurological disorders, thus promoting the search for novel NaV channel ligands. With the objective of discovering new blockers of NaV channel ligands, we screened an In-House vegetal alkaloid library using fluorescence cell-based assays. We screened 62 isoquinoline alkaloids (IA) for their ability to decrease the FRET signal of voltage sensor probes (VSP), which were induced by the activation of NaV channels with batrachotoxin (BTX) in GH3b6 cells. This led to the selection of five IA: liriodenine, oxostephanine, thalmiculine, protopine, and bebeerine, inhibiting the BTX-induced VSP signal with micromolar IC50. These five alkaloids were then assayed using the Na+ fluorescent probe ANG-2 and the patch-clamp technique. Only oxostephanine and liriodenine were able to inhibit the BTX-induced ANG-2 signal in HEK293-hNaV1.3 cells. Indeed, liriodenine and oxostephanine decreased the effects of BTX on Na+ currents elicited by the hNaV1.3 channel, suggesting that conformation change induced by BTX binding could induce a bias in fluorescent assays. However, among the five IA selected in the VSP assay, only bebeerine exhibited strong inhibitory effects against Na+ currents elicited by the hNav1.2 and hNav1.6 channels, with IC50 values below 10 µM. So far, bebeerine is the first BBIQ to have been reported to block NaV channels, with promising therapeutical applications.

Blood platelets produced by bone marrow megakaryocytes play a fundamental role in the initiation of endogenous hemostasis and effective endothelial repair following vascular injury. Although most platelets are found circulating inactivated in the intact vasculature, they rapidly become activated on vessel wall injury and adhere to the exposed extracellular matrix to form a platelet plug, thereby preventing blood loss. Although the activation of platelets is mediated by diverse agonists including subendothelial collagens, thromboxane A2, adenosine diphosphate (ADP), and thrombin, which act on different platelet receptors and initiate distinct signaling pathways, they all converge to an elevation of the intracellular calcium (Ca2+) concentration ([Ca2+]i) that drives platelet conformational change, degranulation, and inside‐out activation of integrin αIIbβ3 essential for platelet aggregation.1.Varga‐Szabo D. Braun A. Nieswandt B. Calcium signaling in platelets.J Thromb Haemost. 2009; 7: 1057-1066Crossref PubMed Scopus (347) Google Scholar Numerous studies have investigated the signaling pathways and molecular players contributing to Ca2+ mobilization during platelet activation. Whereas the release of Ca2+ from intracellular stores via inositol 1,4,5‐trisphosphate (IP3) receptors (IP3Rs) plays a major role in the elevation of [Ca2+]i during platelet activation, several studies have reported on the importance of extracellular Ca2+ entry through the plasma membrane. For instance, it is established that IP3‐mediated Ca2+ release from internal stores in turns triggers store‐operated Ca2+ (SOC) entry through Orai1 channels in the plasma membrane.2.Braun A. Varga‐Szabo D. Kleinschnitz C. et al.Orai1 (CRACM1) is the platelet SOC channel and essential for pathological thrombus formation.Blood. 2009; 113: 2056-2063Crossref PubMed Scopus (211) Google Scholar In addition, a significant influx of Ca2+ also occurs via ATP‐gated purinergic P2X1 receptors3.Mahaut‐Smith M.P. Jones S. Evans R.J. The P2X1 receptor and platelet function.Purinergic Signal. 2011; 7: 341-356Crossref PubMed Scopus (52) Google Scholar and canonical transient receptor potential TRPC6 channels.4.Paez Espinosa E.V. Lin O.A. Karim Z.A. Alshbool F.Z. Khasawneh F.T. Mouse transient receptor potential channel type 6 selectively regulates agonist‐induced platelet function.Biochem Biophys Rep. 2019; 20PubMed Google Scholar In contrast, the implication of plasma membrane voltage‐gated Ca2+ channels (VGCCs) in platelet Ca2+ homeostasis has remained elusive. Early studies using pharmacological blockers and radioligand binding assays have ruled out on the implication of L‐type VGCCs in human platelets.5.Doyle V.M. Rüegg U.T. Lack of evidence for voltage dependent calcium channels on platelets.Biochem Biophys Res Commun. 1985; 127: 161-167Crossref PubMed Scopus (80) Google Scholar, 6.Pannocchia A. Praloran N. Arduino C. et al.Absence of (−) [3H]desmethoxyverapamil binding sites on human platelets and lack of evidence for voltage‐dependent calcium channels.Eur J Pharmacol. 1987; 142: 83-91Crossref PubMed Scopus (14) Google Scholar, 7.Zschauer A. van Breemen C. Bühler F.R. Nelson M.T. Calcium channels in thrombin‐activated human platelet membrane.Nature. 1988; 334: 703-705Crossref PubMed Scopus (80) Google Scholar However, decreased platelet activation was reported in hypertensive patients with type 2 diabetes treated with efonidipine, a dual L‐ and T‐type VGCC blocker, suggesting that T‐type channels could possibly contribute to platelet homeostasis.8.Nomura S. Kanazawa S. Fukuhara S. Effects of efonidipine on platelet and monocyte activation markers in hypertensive patients with and without type 2 diabetes mellitus.J Hum Hypertens. 2002; 16: 539-547Crossref PubMed Scopus (102) Google Scholar In an elegant study published in this issue of Journal of Thrombosis and Haemostasis, Tamang and colleagues report on the expression of T‐type channels and reveal their role in platelet Ca2+ homeostasis.9.Tamang H.K. Yang R.B. Song Z.H. et al.Cav 3.2 T‐type calcium channel regulates mouse platelet activation and arterial thrombosis.J Thromb Haemost. 2022; Abstract Full Text Full Text PDF PubMed Scopus (2) Google Scholar T‐type channels encompass a subfamily of VGCCs consisting of Cav3.1, Cav3.2, and Cav3.3 channels.10.Weiss N. Zamponi G.W. T‐type calcium channels: from molecule to therapeutic opportunities.Int J Biochem Cell Biol. 2019; 108: 34-39Crossref PubMed Scopus (55) Google Scholar Although T‐type channels are predominantly expressed in excitable cells where they contribute to shaping electrical activities and low‐threshold exocytosis,11.Weiss N. Zamponi G.W. Control of low‐threshold exocytosis by T‐type calcium channels.Biochim Biophys Acta. 2013; 1828: 1579-1586Crossref PubMed Scopus (49) Google Scholar numerous studies have also documented their presence in nonexcitable tissues.12.Antal L. Martin‐Caraballo M. T‐type calcium channels in cancer.Cancers. 2019; 11: E134Crossref PubMed Scopus (36) Google Scholar Using Western blot analysis, Tamang and colleagues demonstrate that Cav3.2 (but not Cav3.1) is expressed in mouse platelets. Importantly, no Cav3.2 immunoreactivity was detected in platelets from Cav3.2 knockout mice (Cav3.2−/−), indicative of the specificity of their biochemical analysis. The authors further document using Ca2+ imaging that [Ca2+]i elevation in response to thrombin activation is reduced in Cav3.2−/− platelets as well as upon pharmacological inhibition of Cav3.2 channels by low Ni2+ concentrations (30 μM) without apparent alterations of intracellular Ca2+ release and SOC entry. Alteration of Ca2+ homeostasis in Cav3.2−/− platelets was associated with reduced ERK phosphorylation, reduced integrin αIIbβ3 activation, reduced ATP release, and reduced platelet aggregation. Moving forward, the authors used an in vivo model of ferric chloride–induced arterial thrombosis and show that blood occlusion time at injured carotid artery is reduced in Cav3.2−/− mice, as well as in mice where Cav3.2 is selectively knocked out in platelets (Cav3.2plt−/−). However, these results were not recapitulated in a tail bleeding assay. Overall, Tamang and colleagues convincingly show that Cav3.2 channels are functionally expressed in mouse platelets where they contribute to [Ca2+]i elevation in response to aggregating agents. Although T‐type channels are predominantly inactivated at rest, their unique voltage‐dependent gating properties generate a window current in which a small fraction of channels remain active near typical resting membrane potentials. Given that the resting membrane potential of platelets is estimated to be around −60 mV13.MacIntyre D.E. Rink T.J. The role of platelet membrane potential in the initiation of platelet aggregation.Thromb Haemost. 1982; 47: 22-26Crossref PubMed Scopus (46) Google Scholar and falls within the T‐type window current, it is a possibility that a passive influx of Ca2+ may occur through Cav3.2 channels. Although this may have important physiological consequence on platelet Ca2+ homeostasis at rest, the question then arises as to how Ca2+ influx through Cav3.2 could possibly contribute to [Ca2+]i elevation in response to aggregating agents. Interestingly, an early study aiming at tracking the membrane potential of human platelets reported a transient hyperpolarizing shift up to ‐22 mV in response to thrombin stimulation.14.Horne W.C. Simons E.R. Probes of transmembrane potentials in platelets: changes in cyanine dye fluorescence in response to aggregation stimuli.Blood. 1978; 51: 741-749Crossref PubMed Google Scholar This hyperpolarization of the platelet plasma membrane would increase the driving force for Ca2+ influx through Cav3.2 window current and therefore could represent a possible mechanism by which Cav3.2 channels contribute to thrombin‐induced [Ca2+]i elevation (Figure 1). However, thrombin‐induced hyperpolarization was only observed in response to low thrombin concentrations, whereas high concentrations produced an opposing effect14.Horne W.C. Simons E.R. Probes of transmembrane potentials in platelets: changes in cyanine dye fluorescence in response to aggregation stimuli.Blood. 1978; 51: 741-749Crossref PubMed Google Scholar suggesting that the contribution of Cav3.2 channels to platelet activation may be particularly relevant in situations in which aggregating agents are produced at low levels. In addition to the role of the membrane potential in Cav3.2‐mediated Ca2+ influx, it is also a possibility that aggregating agents may directly affect the gating properties of the channels. For instance, it was reported that the open probability of L‐type VGCCs in cardiomyocytes is enhanced upon application of thrombin via an intracellular signaling pathway that likely involves the phosphorylation of the channels.15.Albitz R. Droogmans G. Nilius B. Casteels R. Thrombin stimulates L‐type calcium channels of Guinea pig cardiomyocytes in cell‐attached patches but not after intracellular dialysis.Cell Calcium. 1992; 13: 203-210Crossref PubMed Scopus (15) Google Scholar Whether such a regulation applies to Cav3.2 channels will need to be investigated. In conclusion, the study by Tamang and colleagues provides compelling new evidence for a role of Cav3.2 channels in platelet Ca2+ homeostasis. Importantly, the observation that Cav3.2‐mediated Ca2+ entry contributes to platelet activation may have important pathological consequences. For instance, it was reported that application of elevated levels of homocysteine on human platelets triggers [Ca2+]i elevation via T‐type channels.16.Leoncini G. Pascale R. Signorello M.G. Effects of homocysteine on l‐arginine transport and nitric oxide formation in human platelets.Eur J Clin Invest. 2003; 33: 713-719Crossref PubMed Scopus (45) Google Scholar Given that hyperhomocysteinemia is an independent risk factor for atherothrombosis, it is possible that T‐type‐mediated Ca2+ entry may cause platelet hyperactivation and contribute to the thrombogenic processes. On the other hand, these data suggest that Food and Drug Administration–approved T‐type channel blockers for the treatment of epilepsy17.Weiss N. Zamponi G.W. T‐type channel druggability at a crossroads.ACS Chem Nerosci. 2019; 10: 1124-1126Crossref PubMed Scopus (20) Google Scholar could conceivably be repurposed as antiplatelet agent in the prevention of atherothrombosis. Finally, deleterious mutations in the genes encoding for T‐type channels including Cav3.2 have been linked to a number of human conditions including epilepsy, neuromuscular disorders, autism spectrum disorders, chronic pain, and primary aldosteronism.18.Weiss N. Zamponi G.W. Genetic T‐type calcium channelopathies.J Med Genet. 2020; 57: 1-10Crossref PubMed Scopus (38) Google Scholar Considering that platelets have been receiving increasing attention for their role in the modulation of the nervous system and their potential implication in neurological disorders,19.Leiter O. Walker T.L. Platelets: the missing link between the blood and brain.Prog Neurobiol. 2019; 183Crossref PubMed Scopus (32) Google Scholar understanding the impact that Cav3.2 mutations may have on platelet homeostasis may reveal new disease mechanisms of T‐type channelopathies. As the sole author N.W. was responsible for all aspects of the manuscript. The author has no conflict of interest to declare. N.W. is recipient of a grant from the Czech Science Foundation (GACR #22‐23242S).Grantová Agentura České Republiky22‐23242SCzech Science Foundation23242S

Low-voltage-activated T-type Ca 2+ channels are key regulators of neuronal excitability both in the central and peripheral nervous systems. Therefore, their recruitment at the plasma membrane is critical in determining firing activity patterns of nerve cells. In this study, we report the importance of secretory carrier-associated membrane proteins (SCAMPs) in the trafficking regulation of T-type channels. We identified SCAMP2 as a novel Ca v 3.2-interacting protein. In addition, we show that co-expression of SCAMP2 in mammalian cells expressing recombinant Ca v 3.2 channels caused an almost complete drop of the whole cell T-type current, an effect partly reversed by single amino acid mutations within the conserved cytoplasmic E peptide of SCAMP2. SCAMP2-induced downregulation of T-type currents was also observed in cells expressing Ca v 3.1 and Ca v 3.3 channel isoforms. Finally, we show that SCAMP2-mediated knockdown of the T-type conductance is caused by the lack of Ca v 3.2 expression at the cell surface as evidenced by the concomitant loss of intramembrane charge movement without decrease of total Ca v 3.2 protein level. Taken together, our results indicate that SCAMP2 plays an important role in the trafficking of Ca v 3.2 channels at the plasma membrane.

In this brief report, we demonstrate that the Ca(v)3.3 T-type voltage-gated calcium channel subtype is involved in our FRICT-ION model of chronic trigeminal neuropathic pain. We first showed that the Cacna1i gene encoding Ca(v)3.3 is significantly upregulated in whole trigeminal ganglia of FRICT-ION mice compared to controls at week 10 post-injury. We confirmed protein upregulation of Ca(v)3.3 compared to controls using Western blot analysis of whole trigeminal ganglia tissues. Finally, we demonstrated that intraperitoneal injection of a selective TAT-based Ca(v)3.3 blocking peptide in FRICT-ION mice significantly reduces Ca(v)3.3 protein expression at the peak anti-allodynic effect (4 hrs post-injection) of the attenuated neuropathic pain behavior. We also suggest that blockade of Ca(v)3.3 may be more effective in attenuating trigeminal neuropathic pain in female than male FRICT-ION mice. Therefore, blocking or attenuating Ca(v)3.3 function may be an effective strategy for the treatment of trigeminal neuropathic pain.

Developmental and epileptic encephalopathies (DEEs) are a group of severe epilepsies that are characterized by seizures and developmental delay. DEEs are primarily attributed to genetic causes and an increasing number of cases have been correlated with variants in ion channel genes. In this study, we report a child with an early severe DEE. Whole exome sequencing showed a de novo heterozygous variant (c.4873–4881 duplication) in the SCN8A gene and an inherited heterozygous variant (c.952G > A) in the CACNA1H gene encoding for Nav1.6 voltage‐gated sodium and Cav3.2 voltage‐gated calcium channels, respectively. In vitro functional analysis of human Nav1.6 and Cav3.2 chan‐ nel variants revealed mild but significant alterations of their gating properties that were in general consistent with a gain‐ and loss‐of‐channel function, respectively. Although additional studies will be required to confirm the actual pathogenic involvement of SCN8A and CACNA1H, these findings add to the notion that rare ion channel variants may contribute to the etiology of DEEs.