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A hormone is any member of a class of signaling molecules in multicellular organisms, that are transported to distant organs to regulate physiology and / or behavior. Hormones are required for the correct development of animals, plants and fungi. The lax definition of a hormone means that many different classes of molecule can be defined as hormones. Among the substances that can be considered hormones, are eicosanoids, steroids, amino acid derivatives, protein / peptides and gases.
Corticotropin-releasing hormone (CRH) is a peptide hormone involved in the stress response. It is a releasing hormone that belongs to corticotropin-releasing factor family. In humans, it is encoded by the CRH gene. Its main function is the stimulation of the pituitary synthesis of ACTH, as part of the HPA Axis.
Cortisol is a steroid hormone, in the glucocorticoid class of hormones. When used as a medication, it is known as hydrocortisone.
Corticotropin-releasing factor family, CRF family is a family of related neuropeptides in vertebrates. This family includes corticotropin-releasing hormone, urotensin-I, urocortin, and sauvagine. The family can be grouped into 2 separate paralogous lineages, with urotensin-I, urocortin and sauvagine in one group and CRH forming the other group. Urocortin and sauvagine appear to represent orthologues of fish urotensin-I in mammals and amphibians, respectively. The peptides have a variety of physiological effects on stress and anxiety, vasoregulation, thermoregulation, growth and metabolism, metamorphosis and reproduction in various species, and are all released as prohormones.
A hormone receptor is a receptor molecule that binds to a specific hormone. Hormone receptors are a wide family of proteins made up of receptors for thyroid and steroid hormones, retinoids and Vitamin D, and a variety of other receptors for various ligands, such as fatty acids and prostaglandins. There are two main classes of hormone receptors. Receptors for peptide hormones tend to be cell surface receptors built into the plasma membrane of cells and are thus referred to as trans membrane receptors. An example of this is insulin. Receptors for steroid hormones are usually found within the cytoplasm and are referred to as intracellular or nuclear receptors, such as testosterone. Upon hormone binding, the receptor can initiate multiple signaling pathways, which ultimately leads to changes in the behavior of the target cells.
The paraventricular nucleus is a nucleus in the hypothalamus. Anatomically, it is adjacent to the third ventricle and many of its neurons project to the posterior pituitary. These projecting neurons secrete oxytocin and a smaller amount of vasopressin, otherwise the nucleus also secretes corticotropin-releasing hormone (CRH) and thyrotropin-releasing hormone (TRH). CRH and TRH are secreted into the hypophyseal portal system and act on different targets neurons in the anterior pituitary. PVN is thought to mediate many diverse functions through these different hormones, including osmoregulation, appetite, and the response of the body to stress.
Corticotropes are basophilic cells in the anterior pituitary that produce pro-opiomelanocortin (POMC) which undergoes cleavage to adrenocorticotropin (ACTH), β-lipotropin (β-LPH), and melanocyte-stimulating hormone (MSH). These cells are stimulated by corticotropin releasing hormone (CRH) and make up 15–20% of the cells in the anterior pituitary. The release of ACTH from the corticotropic cells is controlled by CRH, which is formed in the cell bodies of parvocellular neurosecretory cells within the paraventricular nucleus of the hypothalamus and passes to the corticotropes in the anterior pituitary via the hypophyseal portal system. Adrenocorticotropin hormone stimulates the adrenal cortex to release glucocorticoids and plays an important role in the stress response.
Releasing hormones and inhibiting hormones are hormones whose main purpose is to control the release of other hormones, either by stimulating or inhibiting their release. They are also called liberins and statins (respectively), or releasing factors and inhibiting factors. The examples are hypothalamic-pituitary hormones that can be classified from several viewpoints: they are hypothalamic hormones, they are hypophysiotropic hormones, and they are tropic hormones.
The hypophyseal portal system is a system of blood vessels in the microcirculation at the base of the brain, connecting the hypothalamus with the anterior pituitary. Its main function is to quickly transport and exchange hormones between the hypothalamus arcuate nucleus and anterior pituitary gland. The capillaries in the portal system are fenestrated which allows a rapid exchange between the hypothalamus and the pituitary. The main hormones transported by the system include gonadotropin-releasing hormone, corticotropin-releasing hormone, growth hormone–releasing hormone, and thyrotropin-releasing hormone.
Urocortin is a protein that in humans is encoded by the UCN gene. Urocortin belongs to the corticotropin-releasing factor (CRF) family of proteins which includes CRF, urotensin I, sauvagine, urocortin II and urocortin III. Urocortin is involved in the mammalian stress response, and regulates aspects of appetite and stress response.
Corticotropin-releasing hormone receptors (CRHRs), also known as corticotropin-releasing factor receptors (CRFRs) are a G protein-coupled receptor family that binds corticotropin-releasing hormone (CRH). There are two receptors in the family, designated as type 1 and 2, each encoded by a separate gene.
Corticotropin-releasing hormone receptor 1 (CRHR1) is a protein, also known as CRF1, with the latter (CRF1) now being the IUPHAR-recommended name. In humans, CRF1 is encoded by the CRHR1 gene.
Corticotropin-releasing hormone receptor 2 (CRHR2) is a protein, also known by the IUPHAR-recommended name CRF2, that is encoded by the CRHR2 gene and occurs on the surfaces of some mammalian cells. CRF2 receptors are type 2 G protein-coupled receptors for corticotropin-releasing hormone (CRH) that are resident in the plasma membranes of hormone-sensitive cells. CRH, a peptide of 41 amino acids synthesized in the hypothalamus, is the principal neuroregulator of the hypothalamic-pituitary-adrenal axis, signaling via guanine nucleotide-binding proteins (G proteins) and downstream effectors such as adenylate cyclase. The CRF2 receptor is a multi-pass membrane protein with a transmembrane domain composed of seven helices arranged in a V-shape. CRF2 receptors are activated by two structurally similar peptides, urocortin II, and urocortin III, as well as CRH.
Corticotropin-releasing factor-binding protein is a protein that in humans is encoded by the CRHBP gene. It belongs to corticotropin-releasing hormone binding protein family.
Secretagogin is a protein that in humans is encoded by the SCGN gene.
Antalarmin (CP-156,181) is a drug that acts as a CRH1 antagonist.
A Corticotropin-Releasing Hormone Antagonist is a specific type of receptor antagonist that blocks the receptor sites for Corticotropin-releasing hormone, also known as corticotropin-releasing factor (CRF), which synchronizes the behavioral, endocrine, autonomic, and immune responses to stress by controlling the hypothalamic-pituitary-adrenal axis. CRH Antagonists thereby block the consequent secretions of ACTH and cortisol due to stress, among other effects.
Parvocellular neurosecretory cells are small neurons within paraventricular nucleus (PVN) of the hypothalamus. The axons of the parvocellular neurosecretory cells of the PVN project to the median eminence, at the base of the brain, where their neurosecretory nerve terminals release peptides into blood vessels in the hypothalamo-pituitary portal system. The blood vessels carry the peptides to the anterior pituitary gland, where they regulate the secretion of hormones into the systemic circulation.
Verucerfont (GSK-561,679) is a drug developed by GlaxoSmithKline which acts as a CRF-1 antagonist. Corticotropin releasing factor (CRF), also known as Corticotropin releasing hormone, is an endogenous peptide hormone which is released in response to various triggers such as chronic stress, and activates the two corticotropin-releasing hormone receptors CRH-1 and CRH-2. This then triggers the release of corticotropin (ACTH), another hormone which is involved in the physiological response to stress.
Sauvagine is a neuropeptide from the corticotropin-releasing factor (CRF) family of peptides and is orthologous to the mammalian hormone, urocortin 1, and the teleost fish hormone, urotensin 1. It is 40 amino acids in length, and has the sequence XGPPISIDLSLELLRKMIEIEKQEKEKQQAANNRLLLDTI-NH2, with a pyrrolidone carboxylic acid modification at the N-terminal and amidation of the C-terminal isoleucine residue. It was originally isolated from the skin of the frog Phyllomedusa sauvagei. Given its relation to other CRF-related peptides, it exerts similar physiological effects as corticotropin-releasing hormone.
References
- ↑ Ketchesin, Kyle D.; Stinnett, Gwen S.; Seasholtz, Audrey F. (2017-09-03). "Corticotropin-releasing hormone-binding protein and stress: from invertebrates to humans". Stress. 20 (5): 449–464. doi:10.1080/10253890.2017.1322575. ISSN 1025-3890. PMC 7885796 . PMID 28436309. S2CID 41347737.
- 1 2 Huising, Mark O.; Flik, Gert (May 2005). "The Remarkable Conservation of Corticotropin-Releasing Hormone (CRH)-Binding Protein in the Honeybee ( Apis mellifera ) Dates the CRH System to a Common Ancestor of Insects and Vertebrates". Endocrinology. 146 (5): 2165–2170. doi: 10.1210/en.2004-1514 . ISSN 0013-7227. PMID 15718273.
- ↑ De Groef, Bert; Van der Geyten, Serge; Darras, Veerle M.; Kühn, Eduard R. (March 2006). "Role of corticotropin-releasing hormone as a thyrotropin-releasing factor in non-mammalian vertebrates". General and Comparative Endocrinology. 146 (1): 62–68. doi:10.1016/j.ygcen.2005.10.014. PMID 16337947.
- ↑ Seasholtz AF, Valverde RA, Denver RJ (2002). "Corticotropin-releasing hormone-binding protein: biochemistry and function from fishes to mammals". J. Endocrinol. 175 (1): 89–97. doi: 10.1677/joe.0.1750089 . PMID 12379493.