Ca2+-independent syntaxin binding to the C2B effector region of synaptotagmin

Although synaptotagmin I, which is a calcium (Ca2+)-binding synaptic vesicle protein, may trigger soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE)-mediated synaptic vesicle exocytosis, the mechanisms underlying the interaction between these proteins remain controversial, especially with respect to the identity of the protein(s) in the SNARE complex that bind(s) to synaptotagmin and whether Ca2+ is required for their highly effective binding. To address these questions, native proteins were solubilized, immunoprecipitated from rat brain extracts, and analyzed by immunoblotting. SNARE complexes comprising syntaxin 1, 25-kDa synaptosomal-associated protein (SNAP-25), and synaptobrevin 2 were coprecipitzted with synaptotagmin I in the presence of ethylene glycol tetraacetic acid. The amount of cop recipitated proteins was significantly unaltered by the addition of Ca2+ to the brain extract. To identify the component of the SNARE complex that bound to synaptotagmin, SNARE was coexpressed with synaptotagmin in HEK293 cells and immunoprecipitated. Syntaxin, but not SNAP-25 and synaptobrevin, bound to synaptotagmin in a Ca2+-independent manner, and the binding was abolished in the presence of 1 M NaCl. Synaptotagmin contains 2 Ca2+-binding domains (C(2)A, C2B). Mutating the positively charged lysine residues in the putative effector-binding region of the C2B domain, which are critical for transmitter release, markedly inhibited synaptotagmin-syntaxin binding, while similar mutations in the C(2)A domain had no effect on binding. Synaptotagmin-syntaxin binding was reduced by mutating multiple negatively charged glutamate residues in the amino-terminal half of the syntaxin SNARE motif. These results indicate that synaptotagmin I binds to syntaxin 1 electrostatically through its C2B domain effector region in a Ca2+-independent fashion, providing biochemical evidence that synaptotagmin I binds SNARE complexes before Ca2+ influx into presynaptic nerve terminals

Actin bundling by dynamin 2 and cortactin is implicated in cell migration by stabilizing filopodia in human non-small cell lung carcinoma cells

The endocytic protein dynamin participates in the formation of actin-based membrane protrusions such as podosomes, pseudopodia, and invadopodia, which facilitate cancer cell migration, invasion, and metastasis. However, the role of dynamin in the formation of actin-based membrane protrusions at the leading edge of cancer cells is unclear. In this study, we demonstrate that the ubiquitously expressed dynamin 2 isoform facilitates cell migration by stabilizing F-actin bundles in filopodia of the lung cancer cell line H1299. Pharmacological inhibition of dynamin 2 decreased cell migration and filopodial formation. Furthermore, dynamin 2 and cortactin mostly colocalized along F-actin bundles in filopodia of serum-stimulated H1299 cells by immunofluorescent and immunoelectron microscopy. Knockdown of dynamin 2 or cortactin inhibited the formation of filopodia in serum-stimulated H1299 cells, concomitant with a loss of F-actin bundles. Expression of wild-type cortactin rescued the punctate-like localization of dynamin 2 and filopodial formation. The incubation of dynamin 2 and cortactin with F-actin induced the formation of long and thick actin bundles, with these proteins colocalizing at F-actin bundles. A depolymerization assay revealed that dynamin 2 and cortactin increased the stability of F-actin bundles. These results indicate that dynamin 2 and cortactin participate in cell migration by stabilizing F-actin bundles in filopodia. Taken together, these findings suggest that dynamin might be a possible molecular target for anticancer therapy

Gene expression profiling of the anti-glioma effect of Cilengitide

Cilengitide (EMD121974), an inhibitor of the adhesive function of integrins, demonstrated preclinical efficacy against malignant glioma. It is speculated that cilengitide can inhibit tumor growth, invasion, and angiogenesis. However, the effects of cilengitide on these processes have not been sufficiently examined. In this study, we investigated the anti-glioma effect of cilengitide using DNA microarray analysis. U87ΔEGFR cells (human malignant glioma cell line) were used for this experiment. The cells were harvested after 16 h of cilengitide treatment, and mRNA was extracted. Gene expression and pathway analyses were performed using a DNA microarray (CodeLink™Human Whole Genome Bioarray). The expression of 265 genes was changed with cilengitide treatment. The expression of 214 genes was up-regulated by more than 4-fold and the expression of 51 genes was down-regulated by more than 4-fold compared to the controls. In pathway analysis, "apoptotic cleavage of cellular proteins" and "TNF receptor signaling pathway" were over-represented. Apoptotic-associated genes such as caspase 8 were up-regulated. Gene expression profiling revealed more detailed mechanism of the anti-glioma effect of cilengitide. Genes associated with apoptosis were over-represented following cilengitide treatment

Self-assembling A6K peptide nanotubes as a mercaptoundecahydrododecaborate (BSH) delivery system for boron neutron capture t (BNCT)

Boron neutron capture therapy (BNCT) is a tumor selective therapy, the effectiveness of which depends on sufficient 10B delivery to and accumulation in tumors. In this study, we used self-assembling A6K peptide nanotubes as boron carriers and prepared new boron agents by simple mixing of A6K and BSH. BSH has been used to treat malignant glioma patients in clinical trials and its drug safety and availability have been confirmed; however, its contribution to BNCT efficacy is low. A6K nanotube delivery improved two major limitations of BSH, including absence of intracellular transduction and non-specific drug delivery to tumor tissue. Varying the A6K peptide and BSH mixture ratio produced materials with different morphologies—determined by electron microscopy—and intracellular transduction efficiencies. We investigated the A6K/BSH 1:10 mixture ratio and found high intracellular boron uptake with no toxicity. Microscopy observation showed intracellular localization of A6K/BSH in the perinuclear region and endosome in human glioma cells. The intracellular boron concentration using A6K/BSH was almost 10 times higher than that of BSH. The systematic administration of A6K/BSH via mouse tail vein showed tumor specific accumulation in a mouse brain tumor model with immunohistochemistry and pharmacokinetic study. Neutron irradiation of glioma cells treated with A6K/BSH showed the inhibition of cell proliferation in a colony formation assay. Boron delivery using A6K peptide provides a unique and simple strategy for next generation BNCT drugs

CACNA1A variants may modify the epileptic phenotype of Dravet syndrome

Dravet syndrome is an intractable epileptic syndrome beginning in the first year of life. De novo mutations of SCN1A, which encode the Na(v)1.1 neuronal voltage-gated sodium channel, are considered the major cause of Dravet syndrome. In this study, we investigated genetic modifiers of this syndrome. We performed a mutational analysis of all coding exons of CACNA1A in 48 subjects with Dravet syndrome. To assess the effects of CACNA1A variants on the epileptic phenotypes of Dravet syndrome, we compared clinical features in two genotype groups: 1) subjects harboring SCN1A mutations but no CACNA1A variants (n=20) and 2) subjects with SCN1A mutations plus CACNA1A variants (n=20). CACNA1A variants detected in patients were studied using heterologous expression of recombinant human Ca(v)2.1 in HEK 293 cells and whole-cell patch-clamp recording. Nine CACNA1A variants, including six novel ones, were detected in 21 of the 48 subjects (43.8%). Based on the incidence of variants in healthy controls, most of the variants seemed to be common polymorphisms. However, the subjects harboring SCN1A mutations and CACNA1A variants had absence seizures more frequently than the patients with only SCN1A mutations (8/20 vs. 0/20, p=0.002). Moreover, the former group of subjects exhibited earlier onset of seizures and more frequent prolonged seizures before one year of age, compared to the latter group of subjects. The electrophysiological properties of four of the five novel Ca(v)2.1 variants exhibited biophysical changes consistent with gain-of-function. We conclude that CACNA1A variants in some persons with Dravet syndrome may modify the epileptic phenotypes

Inhalation of 10% carbon dioxide rapidly terminates Scn1a mutation-related hyperthermia-induced seizures

The aim of this study was to assess the anticonvulsant effect of carbon dioxide (CO2) on Scn1a mutation-related febrile seizures. We examined physiological changes in the blood gas levels after the induction of hyperthermia-induced seizures (HISs), which were associated with the Scn1a missense mutation. We determined the efficacy of inhalation of 5% or 10% CO2 to treat HISs. HISs were evoked in Scn1a mutant and wild-type (WT) rats by hot water baths. To determine the anticonvulsant effect of CO2 inhalation, rats were placed in a chamber filled with air or mixed gas containing 5% CO2 or 10% CO2 for 3 min, immediately after the induction of HISs. We also analyzed the blood gas levels at the end of inhalation of CO2. Hot water bathing induced a significant reduction in the partial pressure of CO2 (pCO2) and respiratory alkalosis in the WT and Scn1a mutant rats. HISs were evoked in 100% of the Scn1a mutant rats within 5 min, but in none of the WT rats. The Scn1a mutant rats demonstrated a higher HISs susceptibility associated with respiratory alkalosis than the WT rats. Inhalation of 10% CO2 shortened the seizure duration from 62.6±12.1 s to 15.5±1.0 s. Blood gas analysis after the inhalation of 10% CO2 demonstrated an elevated pCO2 level and respiratory acidosis. Inhalation of 10% CO2 demonstrated a potent and fast-acting anticonvulsant effect against HISs

RNA editing facilitates the enhanced production of neoantigens during the simultaneous administration of oxaliplatin and radiotherapy in colorectal cancer

Most cases of colorectal cancers (CRCs) are microsatellite stable (MSS), which frequently demonstrate lower response rates to immune checkpoint inhibitors (ICIs). RNA editing produces neoantigens by altering amino acid sequences. In this study, RNA editing was induced artificially by chemoradiation therapy (CRT) to generate neoantigens in MSS CRCs. Altogether, 543 CRC specimens were systematically analyzed, and the expression pattern of ADAR1 was investigated. In vitro and in vivo experiments were also performed. The RNA editing enzyme ADAR1 was upregulated in microsatellite instability-high CRCs, leading to their high affinity for ICIs. Although ADAR1 expression was low in MSS CRC, CRT including oxaliplatin (OX) treatment upregulated RNA editing levels by inducing ADAR1. Immunohistochemistry analyses showed the upregulation of ADAR1 in patients with CRC treated with CAPDX (capecitabine +OX) radiation therapy relative to ADAR1 expression in patients with CRC treated only by surgery (p <0.001). Compared with other regimens, CRT with OX effectively induced RNA editing in MSS CRC cell lines (HT29 and Caco2, p <0.001) via the induction of type 1 interferon-triggered ADAR1 expression. CRT with OX promoted the RNA editing of cyclin I, a neoantigen candidate. Neoantigens can be artificially induced by RNA editing via an OX-CRT regimen. CRT can promote proteomic diversity via RNA editing