Scn1b null mice have a severe neurological and cardiac phenotype. Human mutations in SCN1B result in epilepsy and cardiac arrhythmia. SCN1B is expressed as two developmentally regulated splice variants, β1 and β1B, that are each expressed in brain and heart in rodents and humans. Here we studied the structure and function of β1B and investigated a novel human SCN1B epilepsy-related mutation (p.G257R) unique to β1B. We show that wild-type β1B is not a transmembrane protein, but a soluble protein expressed predominantly during embryonic development that promotes neurite outgrowth. Association of β1B with voltage-gated Na+ channels (VGSCs) Nav1.1 or Nav1.3 is not detectable by immunoprecipitation and β1B does not affect Nav1.3 cell surface expression as measured by [3H]-saxitoxin binding. However, β1B co-expression results in subtle alteration of Nav1.3 currents in transfected cells, suggesting that β1B may modulate Na+ current in brain. Similar to the previously characterized p.R125C mutation, p.G257R results in intracellular retention of β1B, generating a functional null allele. In contrast, two other SCN1B mutations associated with epilepsy, p.C121W and p.R85H, are expressed at the cell surface. We propose that β1B p.G257R may contribute to epilepsy through a mechanism that includes intracellular retention resulting in aberrant neuronal pathfinding.

Purpose: Laryngeal carcinomas always resist to radiotherapy. Hypoxia is an important factor in radioresistance of laryngeal carcinoma. Glucose transporter-1 (GLUT-1) is considered to be a possible intrinsic marker of hypoxia in malignant tumors. We speculated that the inhibition of GLUT-1 expression might improve the radiosensitivity of laryngeal carcinoma. Methods: We assessed the effect of GLUT-1 expression on radioresistance of laryngeal carcinoma and the effect of GLUT-1 expressions by antisense oligodeoxynucleotides (AS-ODNs) on the radiosensitivity of laryngeal carcinoma in vitro and in vivo. Results: After transfection of GLUT-1 AS-ODNs: MTS assay showed the survival rates of radiation groups were reduced with the prolongation of culture time (p<0.05); Cell survival rates were significantly reduced along with the increasing of radiation dose (p<0.05). There was significant difference in the expression of GLUT-1mRNA and protein in the same X-ray dose between before and after X-ray radiation (p<0.05). In vivo, the expressions of GLUT-1 mRNA and protein after 8Gy radiation plus transfection of GLUT-1 AS-ODNs were significant decreased compared to 8Gy radiation alone (p<0.001). Conclusion: Radioresistance of laryngeal carcinoma may be associated with increased expression of GLUT-1 mRNA and protein. GLUT-1 AS-ODNs may enhance the radiosensitivity of laryngeal carcinoma mainly by inhibiting the expression of GLUT-1.

Patients with early infantile epileptic encephalopathy (EIEE) are at increased risk for sudden unexpected death in epilepsy (SUDEP). De novo mutations of the sodium channel gene SCN8A, encoding the sodium channel Na v 1.6, result in EIEE13 (OMIM 614558), which has a 10% risk of SUDEP. Here, we investigated the cardiac phenotype of a mouse model expressing the gain of function EIEE13 patient mutation p.Asn1768Asp in Scn8a (Na v 1.6-N1768D). We tested Scn8a N1768D/+ mice for alterations in cardiac excitability. We observed prolongation of the early stages of action potential (AP) repolarization in mutant myocytes vs. controls. Scn8a N1768D/+ myocytes were hyperexcitable, with a lowered threshold for AP firing, increased incidence of delayed afterdepolarizations, increased calcium transient duration, increased incidence of diastolic calcium release, and ectopic contractility. Calcium transient duration and diastolic calcium release in the mutant myocytes were tetrodotoxin-sensitive. A selective inhibitor of reverse mode Na/Ca exchange blocked the increased incidence of diastolic calcium release in mutant cells. Scn8a N1768D/+ mice exhibited bradycardia compared with controls. This difference in heart rate dissipated after administration of norepinephrine, and there were no differences in heart rate in denervated ex vivo hearts, implicating parasympathetic hyperexcitability in the Scn8a N1768D/+ animals. When challenged with norepinephrine and caffeine to simulate a catecholaminergic surge, Scn8a N1768D/+ mice showed ventricular arrhythmias. Two of three mutant mice under continuous ECG telemetry recording experienced death, with severe bradycardia preceding asystole. Thus, in addition to central neuron hyperexcitability, Scn8a N1768D/+ mice have cardiac myoycte and parasympathetic neuron hyperexcitability. Simultaneous dysfunction in these systems may contribute to SUDEP associated with mutations of Scn8a. sodium channel | epilepsy | arrhythmia | channelopathy | mutation

Hypoxia is an important factor in radioresistance of laryngeal carcinoma. Glucose transporter-1 (GLUT-1) is an important hypoxic marker in malignant tumors, including laryngeal carcinoma. Apigenin is a natural phytoestrogen flavonoid that has potential anticancer effects. Various studies have reported that the effects of apigenin on lowering GLUT-1 expression were involved in downregulation of the PI3K/Akt pathway. Thus, apigenin may improve the radiosensitivity of laryngeal carcinoma by suppressing the expression of GLUT-1 via the PI3K/Akt pathway. The effect of GLUT-1 and PI3K/Akt pathway-related factor expressions by apigenin or antisense oligonucleotides (AS-ODNs) on the radiosensitivity of laryngeal carcinoma in vivo was assessed. The xenograft volume, xenograft weight and apoptosis detection were performed to determine radiosensitivity. The results showed that apigenin or apigenin plus GLUT-1 AS-ODNs improved the radiosensitivity of xenografts. Apigenin or apigenin plus GLUT-1 reduced the expression of GLUT-1, Akt, and PI3K mRNA after X-ray radiation. We found similar results at the protein level. The results suggest that the effects of apigenin on inhibiting xenograft growth and enhancing xenograft radiosensitivity may be associated with suppressing the expression of GLUT-1 via the PI3K/Akt pathway. In addition, apigenin may enhance the effects of GLUT-1 AS-ODNs via the same mechanism.

In the present study, we investigated the role of GLUT-1 and PI3K/Akt signaling in radioresistance of laryngeal carcinoma xenografts. Volume, weight, radiosensitization, and the rate of inhibition of tumor growth in the xenografts were evaluated in different groups. Apoptosis was evaluated by TUNEL assay. In addition, mRNA and protein levels of GLUT-1, p-Akt, and PI3K in the xenografts were measured. Treatment with LY294002, wortmannin, wortmannin plus GLUT-1 AS-ODN, and LY294002 plus GLUT-1 AS-ODN after X-ray irradiation significantly reduced the size and weight of the tumors, rate of tumor growth, and apoptosis in tumors compared to that observed in the 10-Gy group (p<0.05). In addition, mRNA and protein expression of GLUT-1, p-Akt, and PI3K was downregulated. The E/O values of LY294002, LY294002 plus GLUT-1 AS-ODN, wortmannin, and wortmannin plus GLUT-1 AS-ODN were 2.7, 1.1, 1.8, and 1.8, respectively. Taken together, these data indicate that GLUT-1 AS-ODN as well as the inhibitors of PI3K/Akt signaling may act as radiosensitizers of laryngeal carcinoma in vivo.