Voltage-sensitive calcium channels (VSCC) mediate the entry of calcium ions into excitable cells and are also involved in a variety of calcium-dependent processes, including muscle contraction, hormone or neurotransmitter release, gene expression, cell motility, cell division and cell death. The isoform alpha-1B gives rise to N-type calcium currents. N-type calcium channels belong to the 'high-voltage activated' (HVA) group and are blocked by omega-conotoxin-GVIA (omega-CTx-GVIA) and by omega-agatoxin-IIIA (omega-Aga-IIIA). They are however insensitive to dihydropyridines (DHP), and omega-agatoxin-IVA (omega-Aga-IVA). Calcium channels containing alpha-1B subunit may play a role in directed migration of immature neurons.
Interacting selectively and non-covalently with any protein or protein complex (a complex of two or more proteins that may include other nonprotein molecules).
Evidence
1:
Inferred from Physical InteractionIntAct
Large-scale data sets of protein-protein interactions (PPIs) are a valuable resource for mapping and analysis of the topological and dynamic features of interactome networks. The currently available large-scale PPI data sets only contain information on interaction partners. The data presented in this study also include the sequences involved in the interactions (i.e., the interacting regions, IRs) suggested to correspond to functional and structural domains. Here we present the first large-scale IR data set obtained using mRNA display for 50 human transcription factors (TFs), including 12 transcription-related proteins. The core data set (966 IRs; 943 PPIs) displays a verification rate of 70%. Analysis of the IR data set revealed the existence of IRs that interact with multiple partners. Furthermore, these IRs were preferentially associated with intrinsic disorder. This finding supports the hypothesis that intrinsically disordered regions play a major role in the dynamics and diversity of TF networks through their ability to structurally adapt to and bind with multiple partners. Accordingly, this domain-based interaction resource represents an important step in refining protein interactions and networks at the domain level and in associating network analysis with biological structure and function.
Evidence
2:
Inferred from Physical InteractionUniProtKB
To define the role of the Rab3-interacting molecule RIM in exocytosis we searched for additional binding partners of the protein. We found that the two C(2) domains of RIM display properties analogous to those of the C(2)B domain of synaptotagmin-I. Thus, RIM-C(2)A and RIM-C(2)B bind in a Ca(2+)-independent manner to alpha1B, the pore-forming subunit of N-type Ca(2+) channels (EC(50) = approximately 20 nm). They also weakly interact with the alpha1C but not the alpha1D subunit of L-type Ca(2+) channels. In addition, the C(2) domains of RIM associate with SNAP-25 and synaptotagmin-I. The binding affinities for these two proteins are 203 and 24 nm, respectively, for RIM-C(2)A and 224 and 16 nm for RIM-C(2)B. The interactions of the C(2) domains of RIM with SNAP-25 and synaptotagmin-I are modulated by Ca(2+). Thus, in the presence of Ca(2+) (EC(50) = approximately 75 microm) the interaction with synaptotagmin-I is increased, whereas SNAP-25 binding is reduced. Synaptotagmin-I binding is abolished by mutations in two positively charged amino acids in the C(2) domains of RIM and by the addition of inositol polyphosphates. We propose that the Rab3 effector RIM is a scaffold protein that participates through its multiple binding partners in the docking and fusion of secretory vesicles at the release sites.
Interacting selectively and non-covalently with a protein C-terminus, the end of any peptide chain at which the 1-carboxy function of a constituent amino acid is not attached in peptide linkage to another amino-acid residue.
Evidence
1:
Inferred from Physical InteractionUniProtKB
Phosphorylation and dephosphorylation are primary means for rapid regulation of a variety of neuronal functions, such as membrane excitability, neurotransmitter release, and gene expression. Voltage-gated Ca2+ channels are targets for phosphorylation by a variety of second messengers through activation of different types of protein kinases (PKs). Protein phosphatases (PPs), like PKs, are equally important in regulating Ca2+ channels in neurons. However, much less is understood about whether and how a particular type of PP contributes to regulating neuronal Ca2+ channel activities. This is primarily because of the lack of specific inhibitors/activators for different types of PPs, particularly the PP2c family. The functional roles of PP2c and its substrates in the brain remain virtually unknown. During our yeast two-hybrid screening, PP2calpha was pulled out by both N- and P/Q-type Ca2+ channel C termini. This raised the possibility that PP2calpha might be associated with voltage-gated Ca2+ channels for regulation of the Ca(2+) channel activity. Biochemical studies show that PP2calpha binds directly to neuronal Ca2+ channels forming a functional protein complex in vivo. PP2calpha, unlike PP1, PP2a and PP2b, is more effective in dephosphorylation of neuronal Ca2+ channels after their phosphorylation by PKC. In hippocampal neurons, disruption of the PP2calpha-Ca2+ channel interaction significantly enhances the response of Ca2+ channels to modulation by PKC. Thus, the PP2calpha-Ca2+ channel complex is responsible for rapid dephosphorylation of Ca2+ channels and may contribute to regulation of synaptic transmission in neurons.
Catalysis of the transmembrane transfer of a calcium ion by a voltage-gated channel. A voltage-gated channel is a channel whose open state is dependent on the voltage across the membrane in which it is embedded.
The directed movement of substances (such as macromolecules, small molecules, ions) into, out of or within a cell, or between cells, or within a multicellular organism by means of some agent such as a transporter or pore.
N-type calcium channels are omega-conotoxin (omega-CgTx)-sensitive, voltage-dependent ion channels involved in the control of neurotransmitter release from neurons. Multiple subtypes of voltage-dependent calcium channel complexes exist, and it is the alpha 1 subunit of the complex that forms the pore through which calcium enters the cell. The primary structures of human neuronal calcium channel alpha 1B subunits were deduced by the characterization of overlapping complementary DNAs. Two forms (alpha 1B-1 and alpha 1B-2) were identified in human neuroblastoma (IMR32) cells and in the central nervous system, but not in skeletal muscle or aorta tissues. The alpha 1B-1 subunit directs the recombinant expression of N-type calcium channel activity when it is transiently co-expressed with human neuronal beta 2 and alpha 2b subunits in mammalian HEK293 cells. The recombinant channel was irreversibly blocked by omega-CgTx but was insensitive to dihydropyridines. The alpha 1B-1 alpha 2b beta 2-transfected cells displayed a single class of saturable, high-affinity (dissociation constant = 55 pM) omega-CgTx binding sites. Co-expression of the beta 2 subunit was necessary for N-type channel activity, whereas the alpha 2b subunit appeared to modulate the expression of the channel. The heterogeneity of alpha 1B subunits, along with the heterogeneity of alpha 2 and beta subunits, is consistent with multiple, biophysically distinct N-type calcium channels.
Protein involved in the transport of calcium ions. Calcium is essential for a variety of bodily functions, such as neurotransmission, muscle contraction and proper heart function.
Protein involved in the transport of ions. Such proteins are usually transmembrane and mediate a movement of ions across cell membranes. Transport may be passive (facilitated diffusion; down the electrochemical gradient), or active (against the electrochemical gradient). Active transport requires energy which may come from light, oxidation reactions, ATP hydrolysis, or cotransport of other ions or molecules.
Protein involved in the transport of a molecule (metabolite, protein, etc), a ion or an electron across cell membranes, inside the cell or in a tissue fluid.
Cell membrane glycoprotein forming a channel in a biological membrane selectively permeable to calcium ions. Calcium is essential for a variety of bodily functions, such as neurotransmission, muscle contraction and proper heart function.
Protein which is part of a transmembrane protein complex that forms a hydrophilic channel across the lipid bilayer through which specific inorganic ions can diffuse down their electrochemical gradients. The channels are usually gated and only open in response to a specific stimulus, such as a change in membrane potential (voltage-gated) or the binding of a ligand (ligand-gated channel).
Protein which is a component of a voltage-gated channel. Voltage-gated ion channels are responsible for the electrical activity in a variety of cell types. They probably exist in all life forms.
A reference proteome is a set of protein sequences derived from a complete proteome which constitutes a defined standard for a particular user community. Reference proteomes are manually defined according to a number of criteria. They cover the proteomes of well- studied model organisms and other proteomes of interest for biomedical and biotechnological research. Reference proteomes have been selected to provide broad coverage of the tree of life, and constitute a representative cross-section of the taxonomic diversity to be found within UniProtKB.
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