Urocortin is a

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residue (biochemistry), residues. Proteins perform a vast array of functions within organisms, including Enzyme catalysis, catalysing metab ...

that in humans is encoded by the ''UCN''

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

. Urocortin belongs to the

corticotropin-releasing factor Corticotropin-releasing factor family, CRF family is a family of related neuropeptides in vertebrates. This family includes corticotropin-releasing hormone (also known as CRF), urotensin-I, urocortin, and sauvagine. The family can be grouped i ...

(CRF) family of proteins which includes CRF, urotensin I,

sauvagine 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 ...

, urocortin II and urocortin III. Urocortin is involved in the mammalian stress response, and regulates aspects of appetite and stress response.

Structure, localization, and interactions

Urocortin is a

peptide Peptides are short chains of amino acids linked by peptide bonds. A polypeptide is a longer, continuous, unbranched peptide chain. Polypeptides that have a molecular mass of 10,000 Da or more are called proteins. Chains of fewer than twenty am ...

composed of 40

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although over 500 amino acids exist in nature, by far the most important are the 22 α-amino acids incorporated into proteins. Only these 22 a ...

s. Urocortin is composed of a single

alpha helix An alpha helix (or α-helix) is a sequence of amino acids in a protein that are twisted into a coil (a helix). The alpha helix is the most common structural arrangement in the Protein secondary structure, secondary structure of proteins. It is al ...

structure. The human ''UCN'' gene contains two exons, and the entirety of the coding region is contained within the second exon. Urocortin is expressed widely in the central and peripheral nervous systems, with a pattern similar to that of CRF. Areas of similarity between urocortin and CRF expression include the

supraoptic nucleus The supraoptic nucleus (SON) is a nucleus of magnocellular neurosecretory cells in the hypothalamus of the mammalian brain. The nucleus is situated at the base of the brain, adjacent to the optic chiasm. In humans, the SON contains about 3,000 ...

and the

hippocampus The hippocampus (: hippocampi; via Latin from Ancient Greek, Greek , 'seahorse'), also hippocampus proper, is a major component of the brain of humans and many other vertebrates. In the human brain the hippocampus, the dentate gyrus, and the ...

. Urocortin is also expressed in areas distinct from CRF expression; these areas notably include the

median eminence The median eminence is generally defined as the portion of the ventral hypothalamus from which the portal vessels arise. The median eminence is a small swelling on the tuber cinereum, posterior to and on top of the pituitary stalk; it lies in th ...

, the Edinger-Westphal nucleus, and the sphenoid nucleus. Additionally, Urocortin is expressed in peripheral tissues such as the heart. Urocortin is known to interact both with the CRF type 1 and CRF type 2 receptors. Furthermore, Urocortin is thought to be the primary ligand for the CRF type 2 receptor, as it has higher binding affinity for the CRF type 2 receptor than CRF. Additionally, urocortin interacts with CRF Binding Protein in the mammalian brain.

Stress response and social behavior

Urocortin is closely related to CRF, which mediates the mammalian stress response. Urocortin is consequently implicated in a number of stress responses, primarily relating to appetite and food intake. Administration of urocortin to the central nervous system of mice and rats has been shown to decrease appetite. Additionally, central urocortin treatment increases anxiety-linked behaviors and increases motor activity in mice and rats. These general anxiety-linked behaviors are likely induced through the CRF type 1 receptor, and the appetite behaviors are likely induced through the CRF type 2 receptor. The reduction in appetite from urocortin treatment could be a result of suppression of gastric emptying and/or hypoglycemia, which have been shown to result from urocortin treatment. Urocortin expression is stimulated in response to osmotic stress; water deprivation in rats has been shown to induce urocortin expression in the

. Montane Voles and Meadow Voles are closely related species of voles which are regularly studied as a model for social and mating behavior. The distribution of urocortin-expressing neurons differs in meadow voles compared to montane voles, suggesting urocortin may also play a role in modulating social behavior in some species.

Cardiovascular effects

Urocortin has been shown to induce increases in heart rate and coronary blood flow when applied peripherally. These effects are likely mediated through the CRF type 2 receptor, as this receptor is found in the cardiac atria and ventricles. Urocortin also functions to protect cardiovascular tissue from

ischemic Ischemia or ischaemia is a restriction in blood supply to any tissue, muscle group, or organ of the body, causing a shortage of oxygen that is needed for cellular metabolism (to keep tissue alive). Ischemia is generally caused by problems ...

injury. Urocortin's cardiovascular effects separate it from other members of the CRF family, and likely represent its primary biological function.

In non-mammals

Urocortin is not present in all non-mammals; the closet analogue in

teleost Teleostei (; Ancient Greek, Greek ''teleios'' "complete" + ''osteon'' "bone"), members of which are known as teleosts (), is, by far, the largest group of ray-finned fishes (class Actinopterygii), with 96% of all neontology, extant species of f ...

fish is urotensin I. However, in amphibian species such as ''

Xenopus laevis The African clawed frog (''Xenopus laevis''), also known as simply xenopus, African clawed toad, African claw-toed frog or the ''platanna'') is a species of African aquatic frog of the family Pipidae. Its name is derived from the short black ...

'', urocortin is expressed in tissues such as brain, pituitary, kidney, heart, and skin. Urocortin in ''Xenopus'' has been shown to increase

cAMP Camp may refer to: Areas of confinement, imprisonment, or for execution * Concentration camp, an internment camp for political prisoners or politically targeted demographics, such as members of national or minority ethnic groups * Extermination ...

accumulation and inhibit appetite

References

External links