| Granin (chromogranin or secretogranin) | |||||||||
|---|---|---|---|---|---|---|---|---|---|
 Structure of SS-cyclized catestatin fragment from chromogranin A. [1] | |||||||||
| Identifiers | |||||||||
| Symbol | Granin | ||||||||
| Pfam | PF01271 | ||||||||
| InterPro | IPR001990 | ||||||||
| PROSITE | PDOC00365 | ||||||||
| SCOP2 | 1cfk / SCOPe / SUPFAM | ||||||||
| OPM superfamily | 282 | ||||||||
| OPM protein | 1lv4 | ||||||||
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Granin (chromogranin and secretogranin) is a protein family of regulated secretory proteins ubiquitously found in the cores of amine and peptide hormone and neurotransmitter dense-core secretory vesicles. [2]
Granins (chromogranins or secretogranins) are acidic proteins and are present in the secretory granules of a wide variety of endocrine and neuro-endocrine cells. The exact function(s) of these proteins is not yet settled but there is evidence that granins function as pro-hormones, giving rise to an array of peptide fragments for which autocrine, paracrine, and endocrine activities have been demonstrated in vitro and in vivo. The intracellular biochemistry of granins includes binding of Ca2+, ATP and catecholamines (epinephrine, norepinephrine) within the hormone storage vesicle core. There is also evidence that CgA, and perhaps other granins, regulate the biogenesis of dense-core secretory vesicles and hormone sequestration in neuroendocrine cells.
Apart from their subcellular location and the abundance of acidic residues (Asp and Glu), these proteins do not share many structural similarities. Only one short region, located in the C-terminal section, is conserved in all these proteins. Chromogranins and secretogranins together share a C-terminal motif, whereas chromogranins A and B share a region of high similarity in their N-terminal section; this region includes two cysteine residues involved in a disulfide bond.
There are considerable differences in the amino acid composition between different animals. Commercial assays for measuring human CGA can usually not be used for measuring CGA in samples from other species. 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. [3] Region-specific assays measuring defined parts of CGA, CGB and SG2 can be used for measurements in samples from cats and dogs. [4] [5] [6] [7]
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Some other proteins are also proposed to belong to the granins based on their physico-chemical properties. These include NESP55 (SgVI), VGF (SgVII), and ProSAAS (SgVIII). [8]
CGA may refer to:
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.
Human vasopressin, also called antidiuretic hormone (ADH), arginine vasopressin (AVP) or argipressin, is a hormone synthesized from the AVP gene as a peptide prohormone in neurons in the hypothalamus, and is converted to AVP. It then travels down the axon terminating in the posterior pituitary, and is released from vesicles into the circulation in response to extracellular fluid hypertonicity (hyperosmolality). AVP has two primary functions. First, it increases the amount of solute-free water reabsorbed back into the circulation from the filtrate in the kidney tubules of the nephrons. Second, AVP constricts arterioles, which increases peripheral vascular resistance and raises arterial blood pressure.
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Parathyroid chief cells are one of the two cell types of the parathyroid glands, along with oxyphil cells. The chief cells are much more prevalent in the parathyroid gland than the oxyphil cells. It is perceived that oxyphil cells may be derived from chief cells at puberty, as they are not present at birth like chief cells.
Synaptophysin, also known as the major synaptic vesicle protein p38, is a protein that in humans is encoded by the SYP gene.
Digestive enzymes are a group of enzymes that break down polymeric macromolecules into their smaller building blocks, in order to facilitate their absorption into the cells of the body. Digestive enzymes are found in the digestive tracts of animals and in the tracts of carnivorous plants, where they aid in the digestion of food, as well as inside cells, especially in their lysosomes, where they function to maintain cellular survival. Digestive enzymes of diverse specificities are found in the saliva secreted by the salivary glands, in the secretions of cells lining the stomach, in the pancreatic juice secreted by pancreatic exocrine cells, and in the secretions of cells lining the small and large intestines.
Neuroendocrine cells are cells that receive neuronal input and, as a consequence of this input, release messenger molecules (hormones) into the blood. In this way they bring about an integration between the nervous system and the endocrine system, a process known as neuroendocrine integration. An example of a neuroendocrine cell is a cell of the adrenal medulla, which releases adrenaline to the blood. The adrenal medullary cells are controlled by the sympathetic division of the autonomic nervous system. These cells are modified postganglionic neurons. Autonomic nerve fibers lead directly to them from the central nervous system. The adrenal medullary hormones are kept in vesicles much in the same way neurotransmitters are kept in neuronal vesicles. Hormonal effects can last up to ten times longer than those of neurotransmitters. Sympathetic nerve fiber impulses stimulate the release of adrenal medullary hormones. In this way the sympathetic division of the autonomic nervous system and the medullary secretions function together.
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In biology, cell signaling is the process by which a cell interacts with itself, other cells and the environment. Cell signaling is a fundamental property of all cellular life in prokaryotes and eukaryotes.
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Secretoneurin, is a 33-amino acid neuropeptide derived from secretogranin II.
Chromogranin A or parathyroid secretory protein 1 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. In humans, chromogranin A protein is encoded by the CHGA gene.
Carboxypeptidase E (CPE), also known as carboxypeptidase H (CPH) and enkephalin convertase, is an enzyme that in humans is encoded by the CPE gene. This enzyme catalyzes the release of C-terminal arginine or lysine residues from polypeptides.
SCG2, also called secretogranin II (chromogranin C), is a protein which in humans is encoded by the SCG2 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).
Secretogranin III, also known as SCG3, is a protein which in humans is encoded by the SCG3 gene.
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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.