| CHGA | |||||||||||||||||||||||||||||||||||||||||||||||||||
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| Identifiers | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Aliases | CHGA , CGA, chromogranin A, Chromogranin A, PHES, PHE5 | ||||||||||||||||||||||||||||||||||||||||||||||||||
| External IDs | OMIM: 118910; MGI: 88394; HomoloGene: 976; GeneCards: CHGA; OMA:CHGA - orthologs | ||||||||||||||||||||||||||||||||||||||||||||||||||
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| Wikidata | |||||||||||||||||||||||||||||||||||||||||||||||||||
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Chromogranin-A (CgA) or parathyroid secretory protein 1 is encoded in the human by the gene CHGA. Cga is a member of the granin family of neuroendocrine secretory proteins. As such, it is located in secretory vesicles of neurons and endocrine cells such as islet beta cell secretory granules in the pancreas. [5]
Examples of cells producing chromogranin-A (CgA) are chromaffin cells of the adrenal medulla, paraganglia, enterochromaffin-like cells and beta cells of the pancreas. It is present in islet beta cell secretory granules. chromogranin-A (CgA)+ Pulmonary neuroendocrine cells account for 0.41% of all epithelial cells in the conducting airway, but are absent from the alveoli.
Chromogranin-A is the precursor to several functional peptides [6] including vasostatin-1, vasostatin-2, pancreastatin, catestatin and parastatin. These peptides negatively modulate the neuroendocrine function of the releasing cell (autocrine) or nearby cells (paracrine).
Chromogranin-A induces and promotes the generation of secretory granules such as those containing insulin in pancreatic islet beta cells.
Chromogranin-A is elevated in pheochromocytomas. [7] It has been identified as autoantigen in type 1 diabetes. [8] A peptide fragment of CgA located in the Vasostatin-1, namely ChgA29-42 has been identified as the antigenic epitope recognized by diabetogenic BDC2.5 T cells from type 1 diabetes prone NOD mice. [9] [10]
It is used as an indicator for pancreas and prostate cancer [11] and in carcinoid syndrome. [12] [13] It might play a role in early neoplasic progression. Chromogranin-A is cleaved by an endogenous prohormone convertase to produce several peptide fragments. See chromogranin A GeneRIFs for references. In immunohistochemistry it can be used to identify a range of neuroendocrine tumours and is highly specific for both benign and malignant cells of this type. [14]
Mass spec data shows that several peptides originating from CHGA (163-194; 194–214; 272–295;) are significantly lower in samples from ulcerative colitis patients compared to control biopsies. [15]
There are considerable differences in the amino acid composition between different species' chromogranin-A . Commercial assays for measuring human CgA can usually not be used for measuring CgA in samples from other animals. Some specific parts of the molecule have a higher degree of amino acid homology and methods where the antibodies are directed against specific epitopes can be used to measure samples from different animals. [16] Region-specific assays measuring defined parts of CgA, CGB and SG2 can be used for measurements in samples from cats and dogs. [17] [18] [19] [20] [21] In dogs, the catestatin concentration showed weak negative associations with left atrial and ventricular sizes and the catestatin concentration showed weak positive associations with blood pressure. [22]
Variants exist for pancreastatin in various populations of the world. The variant Glycine297Serine has been shown to be more potent in inhibiting insulin-induced glucose uptake, resulting in higher risk of insulin resistance and diabetes among carriers of this variant. A team of researchers led by the Indian Institute of Technology Madras has found that the Glycine297Serine variation was present in approximately 15 percent of Indian and other South Asian populations. [23] [24]
Pro-opiomelanocortin (POMC) is a precursor polypeptide with 241 amino acid residues. POMC is synthesized in corticotrophs of the anterior pituitary from the 267-amino-acid-long polypeptide precursor pre-pro-opiomelanocortin (pre-POMC), by the removal of a 26-amino-acid-long signal peptide sequence during translation. POMC is part of the central melanocortin system.
The major histocompatibility complex (MHC) is a large locus on vertebrate DNA containing a set of closely linked polymorphic genes that code for cell surface proteins essential for the adaptive immune system. These cell surface proteins are called MHC molecules.
An epitope, also known as antigenic determinant, is the part of an antigen that is recognized by the immune system, specifically by antibodies, B cells, or T cells. The part of an antibody that binds to the epitope is called a paratope. Although epitopes are usually non-self proteins, sequences derived from the host that can be recognized are also epitopes.
Synaptophysin, also known as the major synaptic vesicle protein p38, is a protein that in humans is encoded by the SYP gene.
MHC class I molecules are one of two primary classes of major histocompatibility complex (MHC) molecules and are found on the cell surface of all nucleated cells in the bodies of vertebrates. They also occur on platelets, but not on red blood cells. Their function is to display peptide fragments of proteins from within the cell to cytotoxic T cells; this will trigger an immediate response from the immune system against a particular non-self antigen displayed with the help of an MHC class I protein. Because MHC class I molecules present peptides derived from cytosolic proteins, the pathway of MHC class I presentation is often called cytosolic or endogenous pathway.
Agouti-related protein (AgRP), also called agouti-related peptide, is a neuropeptide produced in the brain by the AgRP/NPY neuron. It is synthesized in neuropeptide Y (NPY)-containing cell bodies located in the ventromedial part of the arcuate nucleus in the hypothalamus. AgRP is co-expressed with NPY and acts to increase appetite and decrease metabolism and energy expenditure. It is one of the most potent and long-lasting of appetite stimulators. In humans, the agouti-related peptide is encoded by the AGRP gene.
In immunology, epitope mapping is the process of experimentally identifying the binding site, or epitope, of an antibody on its target antigen. Identification and characterization of antibody binding sites aid in the discovery and development of new therapeutics, vaccines, and diagnostics. Epitope characterization can also help elucidate the binding mechanism of an antibody and can strengthen intellectual property (patent) protection. Experimental epitope mapping data can be incorporated into robust algorithms to facilitate in silico prediction of B-cell epitopes based on sequence and/or structural data.
Proprotein convertase 2 (PC2) also known as prohormone convertase 2 or neuroendocrine convertase 2 (NEC2) is a serine protease and proprotein convertase PC2, like proprotein convertase 1 (PC1), is an enzyme responsible for the first step in the maturation of many neuroendocrine peptides from their precursors, such as the conversion of proinsulin to insulin intermediates. To generate the bioactive form of insulin, a second step involving the removal of C-terminal basic residues is required; this step is mediated by carboxypeptidases E and/or D. PC2 plays only a minor role in the first step of insulin biosynthesis, but a greater role in the first step of glucagon biosynthesis compared to PC1. PC2 binds to the neuroendocrine protein named 7B2, and if this protein is not present, proPC2 cannot become enzymatically active. 7B2 accomplishes this by preventing the aggregation of proPC2 to inactivatable forms. The C-terminal domain of 7B2 also inhibits PC2 activity until it is cleaved into smaller inactive forms that lack carboxy-terminal basic residues. Thus, 7B2 is both an activator and an inhibitor of PC2. PC2 has been identified in a number of animals, including C. elegans.
Neuroendocrine tumors (NETs) are neoplasms that arise from cells of the endocrine (hormonal) and nervous systems. They most commonly occur in the intestine, where they are often called carcinoid tumors, but they are also found in the pancreas, lung, and the rest of the body.
The glucagon receptor is a 62 kDa protein that is activated by glucagon and is a member of the class B G-protein coupled family of receptors, coupled to G alpha i, Gs and to a lesser extent G alpha q. Stimulation of the receptor results in the activation of adenylate cyclase and phospholipase C and in increased levels of the secondary messengers intracellular cAMP and calcium. In humans, the glucagon receptor is encoded by the GCGR gene.
Secretoneurin, is a 33-amino acid neuropeptide derived from secretogranin II.
Granin is a protein family of regulated secretory proteins ubiquitously found in the cores of amine and peptide hormone and neurotransmitter dense-core secretory vesicles.
SCG2, also called secretogranin II (chromogranin C), is a protein which in humans is encoded by the SCG2 gene.
Receptor-type tyrosine-protein phosphatase-like N, also called "IA-2", is an enzyme that in humans is encoded by the PTPRN gene.
Neuroendocrine protein 7B2 is a protein that in humans is encoded by the SCG5 gene. The protein expressed by this gene is widely distributed in neuroendocrine tissues. It functions as a chaperone protein for the proprotein convertase PC2 by blocking the aggregation of this protein, and is required for the production of an active PC2 enzyme. It is an intrinsically disordered protein that may also function as a chaperone for other aggregating secretory proteins in addition to proPC2. 7B2 has been identified in vertebrates and in invertebrates as low as flatworms and insects. It is also called Sgne1 and Secretogranin V. In C. elegans, it was originally called e7B2 and then renamed Seven B Two. There is a Pfam entry for this protein: Secretogranin_V (PF05281).
3-beta-glucuronosyltransferase 1 (B3GAT1) is an enzyme that in humans is encoded by the B3GAT1 gene, whose enzymatic activity creates the CD57 epitope on other cell surface proteins. In immunology, the CD57 antigen is also known as HNK1 or LEU7. It is expressed as a carbohydrate epitope that contains a sulfoglucuronyl residue in several adhesion molecules of the nervous system.
Secretogranin III, also known as SCG3, is a protein which in humans is encoded by the SCG3 gene.
Rh family, C glycoprotein, also known as RHCG, is a protein that in humans is encoded by the RHCG gene.
Peptide-based synthetic vaccines are subunit vaccines made from peptides. The peptides mimic the epitopes of the antigen that triggers direct or potent immune responses. Peptide vaccines can not only induce protection against infectious pathogens and non-infectious diseases but also be utilized as therapeutic cancer vaccines, where peptides from tumor-associated antigens are used to induce an effective anti-tumor T-cell response.
Neuroendocrine differentiation is a term primarily used in relation to prostate cancers that display a significant neuroendocrine cell population on histopathological examination. These types of prostate cancer comprise true neuroendocrine cancers, such as small cell carcinoma, carcinoid and carcinoid-like tumors, as well as prostatic adenocarcinoma exhibiting focal neuroendocrine phenotype.
