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Toshihisa Ohtsuka - One of the best experts on this subject based on the ideXlab platform.
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double deletion of the active zone proteins cast Elks in the mouse forebrain causes high mortality of newborn pups
Molecular Brain, 2020Co-Authors: Akari Hagiwara, Shun Hamada, Yamato Hida, Toshihisa OhtsukaAbstract:Presynaptic active zone cytomatrix proteins are essential elements of neurotransmitter release machinery that govern neural transmission. Among active zone proteins, cytomatrix at the active zone-associated structural protein (CAST) is known to regulate active zone size in retinal photoreceptors and neurotransmitter release by recruiting Ca(2+) channels at various synapses. However, the role of Elks-a protein from the same family as CAST-and the synergistic roles of CAST/Elks have not been thoroughly investigated, particularly with regard to mouse behavior. Here, we generated Elks conditional KO in mouse forebrain synapses by crossing Elks flox mice with a CaMKII promoter-induced Cre line. Results showed that CAST is dominant at these synapses and that Elks can support CAST function, but is less effective in the Elks single KO. Pups of CAST/Elks double KO in the forebrain were born in Mendelian rations but resulted in eventual death right after the birth. Anatomically, the forebrain neuronal compositions of CAST KO and CAST/Elks double KO mice were indistinguishable, and the sensory neural network from whiskers on the face was identified as barrelette-like patches in the spinal trigeminal nucleus. Therefore, depletion of CAST and Elks disrupts neurotransmission from sensory to motor networks, which can lead to deficits in exploration and failure to suckle.
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role of the active zone protein Elks in insulin secretion from pancreatic β cells
Molecular metabolism, 2019Co-Authors: Mica Oharaimaizumi, Kyota Aoyagi, Toshihisa OhtsukaAbstract:Abstract Background Insulin is stored within large dense-core granules in pancreatic beta (β)-cells and is released by Ca2+-triggered exocytosis with increasing blood glucose levels. Polarized and targeted secretion of insulin from β-cells in pancreatic islets into the vasculature has been proposed; however, the mechanisms related to cellular and molecular localization remain largely unknown. Within nerve terminals, the Ca2+-dependent release of a polarized transmitter is limited to the active zone, a highly specialized area of the presynaptic membrane. Several active zone-specific proteins have been characterized; among them, the CAST/Elks protein family members have the ability to form large protein complexes with other active zone proteins to control the structure and function of the active zone for tight regulation of neurotransmitter release. Notably, Elks but not CAST is also expressed in β-cells, implying that Elks may be involved in polarized insulin secretion from β-cells. Scope of review This review provides an overview of the current findings regarding the role(s) of Elks and other active zone proteins in β-cells and focuses on the molecular mechanism underlying Elks regulation within polarized insulin secretion from islets. Major conclusions Elks localizes at the vascular-facing plasma membrane of β-cells in mouse pancreatic islets. Elks forms a potent insulin secretion complex with L-type voltage-dependent Ca2+ channels on the vascular-facing plasma membrane of β-cells, enabling polarized Ca2+ influx and first-phase insulin secretion from islets. This model provides novel insights into the functional polarity observed during insulin secretion from β-cells within islets at the molecular level. This active zone-like region formed by Elks at the vascular side of the plasma membrane is essential for coordinating physiological insulin secretion and may be disrupted in diabetes.
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Molecular mechanism at the presynaptic active zone
Brain and Nerve, 2011Co-Authors: Toshihisa OhtsukaAbstract:Our higher brain functions such as learning and memory, emotion, and consciousness depend on the precise regulation of complicated neural networks in the brain. Neurons communicate with each other through the synapse, which comprise 3 regions: the presynapse, synaptic cleft, and postsynapse. The active zone (AZ) beneath the presynaptic membrane is the principal site for Ca2+ -dependent neurotransmitter release: AZ is involved in determining the site for docking and synaptic vesicle fusion. Presently, the full molecular composition of AZ is unclear, but it is known to contain several AZ-specific proteins, including cytomatrix of the active zone-associated protein (CAST)/ERC2, Elks, RIM1, Munc13-1, Piccolo/Aczonin, and Bassoon. CAST and Elks are novel active zone proteins that directly bind to Rab3-interacting molecules (RIMs), Bassoon, and Piccolo, and are thought to play a role in neurotransmitter release by binding these to AZ proteins. In this review, current advances in studies on AZ structure and function have been summarized, and the focus is mainly on protein-protein interactions among the AZ proteins.
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CAST and Elks proteins: Structural and functional determinants of the presynaptic active zone
Journal of Biochemistry, 2010Co-Authors: Yasuhiro Hida, Toshihisa OhtsukaAbstract:Cytomatrix at the active zone-associated structural protein (CAST) was first purified from rat brain. It belongs to a protein family with the protein Elks being its close relative. In nerve terminals, these proteins are specifically localized in the active zone (AZ). They have been shown to directly interact with other AZ proteins, including RIM1, Piccolo and Bassoon, and indirectly with Munc13-1 through RIM1, forming a large molecular complex at AZ. Moreover, the direct interaction of CAST with RIM1 and Bassoon appears to be involved in the release of neurotransmitters. However, it still remains elusive how CAST and Elks regulate the assembly and function of AZ during synapse maturation. This review focuses on recent findings about the Elks/CAST family revealed by biochemical strategies and genetic studies, and discusses the potential roles of this protein family in the function and organization of the presynaptic AZ.
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involvement of Elks an active zone protein in exocytotic release from rbl 2h3 cells
Cellular Immunology, 2009Co-Authors: Hidehiro Nomura, Toshihisa Ohtsuka, Satoshi Tadokoro, Masahiko Tanaka, Naohide HirashimaAbstract:Recent studies have indicated that SNARE proteins and their accessory proteins are involved in exocytotic release in mast cells and neurotransmitter release in neuronal cells. These data suggest that a similar molecular mechanism operates in both systems. However, mast and neuronal cells are structurally very different; an active zone is found in neuronal cells. In the present study, we examined the involvement of active zone proteins during exocytosis in mast cells. We found that several active zone proteins are expressed in RBL-2H3 cells and focused on one of those proteins called Elks. Overexpression and knockdown of Elks caused an increase and decrease in exocytotic activity, respectively. Immunocytochemical analysis and live imaging of the expression of YFP-conjugated Elks showed that Elks was translocated to the plasma membrane after antigen stimulation. These results suggest that Elks positively regulates exocytotic release in RBL-2H3 by acting on the plasma membrane upon stimulation.
Tomoko Nakata - One of the best experts on this subject based on the ideXlab platform.
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Elks Elks rab6 interacting cast family member 1
Atlas of genetics and cytogenetics in oncology and haematology, 2011Co-Authors: Tomoko Nakata, Shiro MinamiAbstract:Review on ERC1 (Elks/RAB6-interacting/CAST family member 1), with data on DNA, on the protein encoded, and where the gene is implicated.
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Elks (Elks/RAB6-interacting/CAST family member 1)
Atlas of genetics and cytogenetics in oncology and haematology, 2011Co-Authors: Tomoko Nakata, Shiro MinamiAbstract:Review on ERC1 (Elks/RAB6-interacting/CAST family member 1), with data on DNA, on the protein encoded, and where the gene is implicated.
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differential expression of multiple isoforms of the Elks mrnas involved in a papillary thyroid carcinoma
Genes Chromosomes and Cancer, 2002Co-Authors: Tomoko Nakata, Takashi Yokota, Shiro MinamiAbstract:A novel gene, Elks, whose 5′ portion was fused to the RET gene, was found in a papillary thyroid carcinoma. A cDNA of this gene obtained from a human-brain cDNA library revealed that it encoded a peptide of 948 amino acids, termed Elksα. We identified four other isoforms, which encoded Elksβ, Elksγ, Elksδ, and Elksϵ proteins consisting, respectively, of 992, 720, 1088, and 1116 amino acid residues. Analysis of the gene structure revealed that the isoforms were generated by alternative splicing. Isoforms β, γ, δ, and ϵ all contain an optional exon (exon14a), but Elksγ, -δ, and -ϵ lack exon 1b. Elksγ lacks exons 3 to 6. Elksδ and -ϵ lack exons 12 and 17; Elksϵ contains an optional exon (exon 6a). Analysis by RT-PCR suggested that Elksα and Elksβ mRNAs are abundant in the brain, Elksδ and Elksϵ mRNAs predominate in testis and thyroid, and Elksϵ mRNA predominates in other tissues. To prove whether the fusion of different Elks isoforms to RET (between Elks coiled-coil domains and the RET kinase domain) could produce chimeric proteins that could be autophosphorylated, we synthesized Elksγ-RET, Elksδ-RET, and Elksϵ-RET fusion proteins in vitro. Immunoblotting with anti-Elks, anti-RET, and anti-phosphotyrosine antibodies demonstrated that the chimeric proteins were constitutively phosphorylated at tyrosine residues, whereas native RET protein was not. These results indicate that the Elks gene is alternatively spliced, and that every type of Elks-RET chimeric protein having oligomerization domains can activate RET's cytoplasmic tyrosine kinase. © 2002 Wiley-Liss, Inc.
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genomic organization and chromosomal mapping of Elks a gene rearranged in a papillary thyroid carcinoma
Journal of Human Genetics, 2000Co-Authors: Takashi Yokota, Tomoko Nakata, Shiro Minami, Jyoji InazawaAbstract:We recently isolated a novel cDNA, designated Elks, that was fused to RET cDNA in a papillary thyroid carcinoma. Its encoded polypeptide sequence was rich in glutamic acid (E), leucine (L), lysine (K), and serine (S), and was characterized by the presence of nine alpha-helical coiled-coil domains consisting of periodic heptad repeats. We have now cloned the entire structure of the human Elks gene from within a 700-kb genomic region represented by overlapping bacteriophage P1-derived artificial chromosome (PAC) and bacterial artificial chromosome (BAC) clones, and localized it to chromosomal band 12p13.3 by fluorescence in situ hybridization. The gene is approximately 500 kb long, with 19 exons and 18 introns; the transcription initiation site within exon 1 is separate from the initiation codon (in exon 2). Analysis of the exon/intron structure revealed that introns interrupt the coding sequence in such a way that many functional segments of the protein are encoded by distinct exons. Exon 1 encodes the 5′ non-coding region; exons 2, 3, 6, 7, 8, 9, 11, 14, and 15 encode the nine coiled-coil domains. Exons 17–19 constitute the 3′ non-coding region. Analysis of the region immediately upstream of exon 1 showed that it was extremely rich in G/C nucleotides and contained multiple Sp-1 and AP2 binding sequences. The Elks-RET gene fusion rearrangement we had observed in a papillary thyroid carcinoma occurred between intron 10 of the Elks gene and intron 11 of RET.
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fusion of a novel gene Elks to ret due to translocation t 10 12 q11 p13 in a papillary thyroid carcinoma
Genes Chromosomes and Cancer, 1999Co-Authors: Tomoko Nakata, Yutaka Kitamura, Kazuo Shimizu, Shigeo Tanaka, Minoru Fujimori, Shiro YokoyamaAbstract:In papillary thyroid carcinomas, the genes for receptor-type tyrosine kinase, RET or TRKA, are sometimes rearranged, resulting in fusion of its tyrosine kinase domain to 5′ portions of several activating genes. In a papillary thyroid carcinoma, we identified a novel gene (Elks), the 5′ portion of which is fused to the RET gene by gene rearrangement due to the translocation t(10;12)(q11;p13). Subsequent cloning of the Elks cDNA revealed that Elks encodes a novel 948 amino acid peptide and is expressed ubiquitously in human tissues. The presence of multiple coiled-coil domains in the Elks product suggests that the Elks protein forms dimers. Since the tyrosine kinase of RET is activated by dimerization that occurs when its ligands bind to the receptor, fusion of RET with the 5′ dimerization domains of Elks would activate its cytoplasmic tyrosine kinase constitutively in papillary thyroid carcinomas. Genes Chromosomes Cancer 25:97–103, 1999. © 1999 Wiley-Liss, Inc.
Pascal S Kaeser - One of the best experts on this subject based on the ideXlab platform.
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Elks active zone proteins as multitasking scaffolds for secretion
Open Biology, 2018Co-Authors: Richard G Held, Pascal S KaeserAbstract:Synaptic vesicle exocytosis relies on the tethering of release ready vesicles close to voltage-gated Ca 2+ channels and specific lipids at the future site of fusion. This enables rapid and efficient neurotransmitter secretion during presynaptic depolarization by an action potential. Extensive research has revealed that this tethering is mediated by an active zone, a protein dense structure that is attached to the presynaptic plasma membrane and opposed to postsynaptic receptors. Although roles of individual active zone proteins in exocytosis are in part understood, the molecular mechanisms that hold the protein scaffold at the active zone together and link it to the presynaptic plasma membrane have remained unknown. This is largely due to redundancy within and across scaffolding protein families at the active zone. Recent studies, however, have uncovered that Elks proteins, also called ERC, Rab6IP2 or CAST, act as active zone scaffolds redundant with RIMs. This redundancy has led to diverse synaptic phenotypes in studies of Elks knockout mice, perhaps because different synapses rely to a variable extent on scaffolding redundancy. In this review, we first evaluate the need for presynaptic scaffolding, and we then discuss how the diverse synaptic and non-synaptic functional roles of Elks support the hypothesis that Elks provides molecular scaffolding for organizing vesicle traffic at the presynaptic active zone and in other cellular compartments.
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Elks controls the pool of readily releasable vesicles at excitatory synapses through its n terminal coiled coil domains
eLife, 2016Co-Authors: Richard G Held, Pascal S KaeserAbstract:Nerve cells in the brain communicate with one another at connections known as synapses: one nerve cell releases signaling molecules called neurotransmitters into the synapse, which are then sensed by the second cell. For the brain to work correctly, it is important that the nerve cells control when and how much neurotransmitter they release. Nerve cells package neurotransmitters into small packets called vesicles. These vesicles can be released at the so-called active zones of each synapse, though only a small subset of vesicles at a synapse are releasable. Many proteins at the active zone control the release of vesicles to influence how nerve cells communicate with each another. Elks is one of the proteins found at the active zones of nerve cells that release either of the two most common neurotransmitters in the brain: glutamate and GABA. Held et al. have now found that the Elks protein affects the release of these two neurotransmitters in different ways in the two types of nerve cells. The experiments showed that the number of releasable neurotransmitter-filled vesicles was lower in mouse nerve cells that release glutamate when the genes for the Elks proteins were deleted in these cells. When the Elks genes were deleted in the nerve cells that release GABA, the number of releasable vesicles remained the same, though the vesicles were less likely to be released. The fact that removing Elks has different effects at these two types of synapses suggests that the active zone is not the same at all synapses. Furthermore, these results imply that Elks is capable of fine-tuning the communication between nerve cells. Future experiments will address how glutamate- and GABA-releasing active zones differ at the molecular and structural levels. Ultimately, this will lead to a better understanding of how information is processed in the brain.
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the active zone protein family Elks supports ca2 influx at nerve terminals of inhibitory hippocampal neurons
The Journal of Neuroscience, 2014Co-Authors: Lydia S Bickford, Thomas C. Südhof, Richard G Held, Hajnalka Nyitrai, Pascal S KaeserAbstract:In a presynaptic nerve terminal, synaptic vesicle exocytosis is restricted to specialized sites called active zones. At these sites, neurotransmitter release is determined by the number of releasable vesicles and their probability of release. Proteins at the active zone set these parameters by controlling the presynaptic Ca2+ signal, and through docking and priming of synaptic vesicles. Vertebrate Elks proteins are enriched at presynaptic active zones, but their functions are not well understood. Elks proteins are produced by two genes in vertebrates, and each gene contributes ∼50% to total brain Elks. We generated knock-out mice for Elks1 and found that its constitutive removal causes lethality. To bypass lethality, and to circumvent redundancy between Elks1 and Elks2 in synaptic transmission, we used a conditional genetic approach to remove both genes in cultured hippocampal neurons after synapses are established. Simultaneous removal of Elks1 and Elks2 resulted in a 50% decrease of neurotransmitter release at inhibitory synapses, paralleled by a reduction in release probability. Removal of Elks did not affect synapse numbers or their electron microscopic appearance. Using Ca2+ imaging, we found that loss of Elks caused a 30% reduction in single action potential-triggered Ca2+ influx in inhibitory nerve terminals, consistent with the deficits in synaptic transmission and release probability. Unlike deletion of the active zone proteins RIM, RIM-BP, or bruchpilot, Elks removal did not lead to a measurable reduction in presynaptic Ca2+ channel levels. Our results reveal that Elks is required for normal Ca2+ influx at nerve terminals of inhibitory hippocampal neurons.
Shiro Minami - One of the best experts on this subject based on the ideXlab platform.
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Elks Elks rab6 interacting cast family member 1
Atlas of genetics and cytogenetics in oncology and haematology, 2011Co-Authors: Tomoko Nakata, Shiro MinamiAbstract:Review on ERC1 (Elks/RAB6-interacting/CAST family member 1), with data on DNA, on the protein encoded, and where the gene is implicated.
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Elks (Elks/RAB6-interacting/CAST family member 1)
Atlas of genetics and cytogenetics in oncology and haematology, 2011Co-Authors: Tomoko Nakata, Shiro MinamiAbstract:Review on ERC1 (Elks/RAB6-interacting/CAST family member 1), with data on DNA, on the protein encoded, and where the gene is implicated.
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differential expression of multiple isoforms of the Elks mrnas involved in a papillary thyroid carcinoma
Genes Chromosomes and Cancer, 2002Co-Authors: Tomoko Nakata, Takashi Yokota, Shiro MinamiAbstract:A novel gene, Elks, whose 5′ portion was fused to the RET gene, was found in a papillary thyroid carcinoma. A cDNA of this gene obtained from a human-brain cDNA library revealed that it encoded a peptide of 948 amino acids, termed Elksα. We identified four other isoforms, which encoded Elksβ, Elksγ, Elksδ, and Elksϵ proteins consisting, respectively, of 992, 720, 1088, and 1116 amino acid residues. Analysis of the gene structure revealed that the isoforms were generated by alternative splicing. Isoforms β, γ, δ, and ϵ all contain an optional exon (exon14a), but Elksγ, -δ, and -ϵ lack exon 1b. Elksγ lacks exons 3 to 6. Elksδ and -ϵ lack exons 12 and 17; Elksϵ contains an optional exon (exon 6a). Analysis by RT-PCR suggested that Elksα and Elksβ mRNAs are abundant in the brain, Elksδ and Elksϵ mRNAs predominate in testis and thyroid, and Elksϵ mRNA predominates in other tissues. To prove whether the fusion of different Elks isoforms to RET (between Elks coiled-coil domains and the RET kinase domain) could produce chimeric proteins that could be autophosphorylated, we synthesized Elksγ-RET, Elksδ-RET, and Elksϵ-RET fusion proteins in vitro. Immunoblotting with anti-Elks, anti-RET, and anti-phosphotyrosine antibodies demonstrated that the chimeric proteins were constitutively phosphorylated at tyrosine residues, whereas native RET protein was not. These results indicate that the Elks gene is alternatively spliced, and that every type of Elks-RET chimeric protein having oligomerization domains can activate RET's cytoplasmic tyrosine kinase. © 2002 Wiley-Liss, Inc.
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genomic organization and chromosomal mapping of Elks a gene rearranged in a papillary thyroid carcinoma
Journal of Human Genetics, 2000Co-Authors: Takashi Yokota, Tomoko Nakata, Shiro Minami, Jyoji InazawaAbstract:We recently isolated a novel cDNA, designated Elks, that was fused to RET cDNA in a papillary thyroid carcinoma. Its encoded polypeptide sequence was rich in glutamic acid (E), leucine (L), lysine (K), and serine (S), and was characterized by the presence of nine alpha-helical coiled-coil domains consisting of periodic heptad repeats. We have now cloned the entire structure of the human Elks gene from within a 700-kb genomic region represented by overlapping bacteriophage P1-derived artificial chromosome (PAC) and bacterial artificial chromosome (BAC) clones, and localized it to chromosomal band 12p13.3 by fluorescence in situ hybridization. The gene is approximately 500 kb long, with 19 exons and 18 introns; the transcription initiation site within exon 1 is separate from the initiation codon (in exon 2). Analysis of the exon/intron structure revealed that introns interrupt the coding sequence in such a way that many functional segments of the protein are encoded by distinct exons. Exon 1 encodes the 5′ non-coding region; exons 2, 3, 6, 7, 8, 9, 11, 14, and 15 encode the nine coiled-coil domains. Exons 17–19 constitute the 3′ non-coding region. Analysis of the region immediately upstream of exon 1 showed that it was extremely rich in G/C nucleotides and contained multiple Sp-1 and AP2 binding sequences. The Elks-RET gene fusion rearrangement we had observed in a papillary thyroid carcinoma occurred between intron 10 of the Elks gene and intron 11 of RET.
David Gates - One of the best experts on this subject based on the ideXlab platform.
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observation of a high performance operating regime with small edge localized modes in the national spherical torus experiment
Nuclear Fusion, 2005Co-Authors: Rajesh Maingi, K Tritz, E D Fredrickson, J Menard, D Stutman, M G Bell, C E Bush, S.a. Sabbagh, R Bell, David GatesAbstract:We report the observation of a high performance scenario in the National Spherical Torus Experiment with very small edge-localized modes (ELMs). These ELMs, individually, have no measurable impact on the stored energy and are observed by several diagnostics. The small ELMs have clear differences as compared with the ELM types reported in the literature, and this operating mode has distinct features compared with other high performance tokamak scenarios with little or no ELMs. The ELM is termed as 'type V', and it has a short-lived n = 1 magnetic precursor oscillation rotating counter to the plasma current and a distinct signature on the soft x-ray system. If we could extrapolate it, this scenario would provide an attractive operating regime for next step fusion experiments.
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observation of a high performance operating regime with small edge localized modes in the national spherical torus experiment
Other Information: PBD: 13 May 2004, 2004Co-Authors: Rajesh Maingi, K Tritz, E D Fredrickson, J Menard, D Stutman, M G Bell, C E Bush, S.a. Sabbagh, R Bell, David GatesAbstract:We report observation of a high performance scenario in the National Spherical Torus Experiment with very small edge-localized modes (ELMs). These ELMs have no measurable impact on stored energy and are consistent with high bootstrap current operation with line average density approaching Greenwald scaling. The ELM perturbation is observed to typically originate near the lower divertor region, as opposed to the outer midplane for ELMs described in the literature. If extrapolable, this scenario would provide an attractive operating regime for next step fusion experiments