Renin

Not to be confused with rennin, the active enzyme in rennet.
Renin

PDB rendering based on 2ren
Available structures
PDB Ortholog search: PDBe, RCSB
Identifiers
SymbolsREN ; HNFJ2
External IDsOMIM: 179820 MGI: 97898 HomoloGene: 20151 IUPHAR: 2413 ChEMBL: 286 GeneCards: REN Gene
EC number3.4.23.15
Orthologs
SpeciesHumanMouse
Entrez597219701
EnsemblENSG00000143839ENSMUSG00000070645
UniProtP00797P06281
RefSeq (mRNA)NM_000537NM_031192
RefSeq (protein)NP_000528NP_112469
Location (UCSC)Chr 1:
204.12 – 204.14 Mb		Chr 1:
133.35 – 133.36 Mb
PubMed search
renin
Identifiers
EC number 3.4.23.15
CAS number 9015-94-5
Databases
IntEnz IntEnz view
BRENDA BRENDA entry
ExPASy NiceZyme view
KEGG KEGG entry
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / EGO

Renin (etymology and pronunciation), also known as an angiotensinogenase, is an enzyme that participates in the body's renin-angiotensin system (RAS)—also known as the renin-angiotensin-aldosterone axis—that mediates extracellular volume (i.e., that of the blood plasma, lymph and interstitial fluid), and arterial vasoconstriction. Thus, it regulates the body's mean arterial blood pressure.

Renin is often improperly referred to as a hormone even though it has no peripheral receptors and rather has an enzymatic activity with which it hydrolyses angiotensinogen to angiotensin I.

Biochemistry and physiology

Structure

The primary structure of renin precursor consists of 406 amino acids with a pre- and a pro-segment carrying 20 and 46 amino acids, respectively. Mature renin contains 340 amino acids and has a mass of 37 kDa.[1]

Secretion

The enzyme renin is secreted by the afferent arterioles of the kidney from specialized cells called granular cells of the juxtaglomerular apparatus in response to three stimuli:

  1. A decrease in arterial blood pressure (that could be related to a decrease in blood volume) as detected by baroreceptors (pressure-sensitive cells). This is the most direct causal link between blood pressure and renin secretion (the other two methods operate via longer pathways).
  2. A decrease in sodium levels in the ultrafiltrate of the nephron. This flow is measured by the macula densa of the juxtaglomerular apparatus.
  3. Sympathetic nervous system activity, which also controls blood pressure, acting through the beta1 adrenergic receptors.

Human renin is secreted by at least 2 cellular pathways: a constitutive pathway for the secretion of prorenin and a regulated pathway for the secretion of mature renin.[2]

Renin-angiotensin system

The renin-angiotensin system, showing role of renin at bottom.[3]

The renin enzyme circulates in the blood stream and breaks down (hydrolyzes) angiotensinogen secreted from the liver into the peptide angiotensin I.

Angiotensin I is further cleaved in the lungs by endothelial-bound angiotensin-converting enzyme (ACE) into angiotensin II, the most vasoactive peptide.[4][5] Angiotensin II is a potent constrictor of all blood vessels. It acts on the smooth muscle and, therefore, raises the resistance posed by these arteries to the heart. The heart, trying to overcome this increase in its 'load', works more vigorously, causing the blood pressure to rise. Angiotensin II also acts on the adrenal glands and releases aldosterone, which stimulates the epithelial cells in the distal tubule and collecting ducts of the kidneys to increase re-absorption of sodium, exchanging with potassium to maintain electrochemical neutrality, and water, leading to raised blood volume and raised blood pressure. The RAS also acts on the CNS to increase water intake by stimulating thirst, as well as conserving blood volume, by reducing urinary loss through the secretion of vasopressin from the posterior pituitary gland.

The normal concentration of renin in adult human plasma is 1.98-24.6 ng/L in the upright position.[6]

Function

Renin activates the renin-angiotensin system by cleaving angiotensinogen, produced by the liver, to yield angiotensin I, which is further converted into angiotensin II by ACE, the angiotensin-converting enzyme primarily within the capillaries of the lungs. Angiotensin II then constricts blood vessels, increases the secretion of ADH and aldosterone, and stimulates the hypothalamus to activate the thirst reflex, each leading to an increase in blood pressure. Renin's primary function is therefore to eventually cause an increase in blood pressure, leading to restoration of perfusion pressure in the kidneys.

Renin is secreted from juxtaglomerular kidney cells, which sense changes in renal perfusion pressure, via stretch receptors in the vascular walls. The juxtaglomerular cells are also stimulated to release renin by signaling from the macula densa. The macula densa sense changes in volume delivery to the distal tubule, and responds to a drop in tubular volume by stimulating renin release in the juxtaglomerular cells. Together, the macula densa and juxtaglomerular cells comprise the juxtaglomerular complex.

Renin secretion is also stimulated by sympathetic nervous stimulation, mainly through beta-1 adrenoceptor activation.

Renin can bind to ATP6AP2, which results in a fourfold increase in the conversion of angiotensinogen to angiotensin I over that shown by soluble renin. In addition, renin binding results in phosphorylation of serine and tyrosine residues of ATP6AP2.[7]

The level of renin mRNA appears to be modulated by the binding of HADHB, HuR and CP1 to a regulatory region in the 3' UTR.[8]

Genetics

The gene for renin, REN, spans 12 kb of DNA and contains 8 introns.[9] It produces several mRNA that encode different REN isoforms.

Model organisms

Model organisms have been used in the study of REN function. A knockout mouse line, called Ren1Ren-1c Enhancer KO was generated.[15] Male and female animals underwent a standardized phenotypic screen to determine the effects of deletion.[13][16] Twenty four tests were carried out on mutant mice and two significant abnormalities were observed. Homozygous mutant animals had a decreased heart rate and an increased susceptibility to bacterial infection.[13] A more detailed analysis of this line indicated plasma creatinine was also increased and males had lower mean arterial pressure than controls.[15]

Clinical applications

Main article: Renin inhibitor

An over-active renin-angiotension system leads to vasoconstriction and retention of sodium and water. These effects lead to hypertension. Therefore, renin inhibitors can be used for the treatment of hypertension.[17][18] This is measured by the plasma renin activity (PRA).

In current medical practice, the renin-angiotensin-aldosterone-System's overactivity (and resultant hypertension) is more commonly reduced using either ACE inhibitors (such as ramipril and perindopril) or angiotensin II receptor blockers (ARBs, such as losartan, irbesartan or candesartan) rather than a direct oral renin inhibitor. ACE inhibitors or ARBs are also part of the standard treatment after a heart attack.

The differential diagnosis of kidney cancer in a young patient with hypertension includes juxtaglomerular cell tumor (reninoma), Wilms' tumor, and renal cell carcinoma, all of which may produce renin.[19]

Measurement

Further information: Plasma renin activity

Renin is usually measured as the plasma renin activity (PRA). PRA is measured specially in case of certain diseases that present with hypertension or hypotension. PRA is also raised in certain tumors.[20] A PRA measurement may be compared to a plasma aldosterone concentration (PAC) as a PAC/PRA ratio.

Discovery and naming

The name renin = ren + -in, "kidney" + "compound". The most common pronunciation in English is /ˈriːnɨn/, but /ˈrɛnɨn/ is also common. Renin was discovered, characterized, and named in 1898 by Robert Tigerstedt, Professor of Physiology, and his student, Per Bergman, at the Karolinska Institute in Stockholm.[21][22]

See also

References

  1. ↑ Imai T, Miyazaki H, Hirose S, Hori H, Hayashi T, Kageyama R et al. (Dec 1983). "Cloning and sequence analysis of cDNA for human renin precursor". Proceedings of the National Academy of Sciences of the United States of America 80 (24): 7405–9. doi:10.1073/pnas.80.24.7405. PMC 389959. PMID 6324167.
  2. ↑ Pratt RE, Flynn JA, Hobart PM, Paul M, Dzau VJ (Mar 1988). "Different secretory pathways of renin from mouse cells transfected with the human renin gene". The Journal of Biological Chemistry 263 (7): 3137–41. PMID 2893797.
  3. ↑ Boulpaep EL, Boron WF (2005). "Integration of Salt and Water Balance; The Adrenal Gland". Medical physiology: a cellular and molecular approach. St. Louis, MO: Elsevier Saunders. pp. 866–867, 1059. ISBN 1-4160-2328-3.
  4. ↑ Fujino T, Nakagawa N, Yuhki K, Hara A, Yamada T, Takayama K et al. (Sep 2004). "Decreased susceptibility to renovascular hypertension in mice lacking the prostaglandin I2 receptor IP". The Journal of Clinical Investigation 114 (6): 805–12. doi:10.1172/JCI21382. PMC 516260. PMID 15372104.
  5. ↑ Brenner & Rector's The Kidney, 7th ed., Saunders, 2004, pp. 2118-2119 Full Text with MDConsult subscription
  6. ↑ Hamilton Regional Laboratory Medicine Program - Laboratory Reference Centre Manual. [deadlink]
  7. ↑ Nguyen G, Delarue F, Burcklé C, Bouzhir L, Giller T, Sraer JD (Jun 2002). "Pivotal role of the renin/prorenin receptor in angiotensin II production and cellular responses to renin". The Journal of Clinical Investigation 109 (11): 1417–27. doi:10.1172/JCI14276. PMC 150992. PMID 12045255.
  8. ↑ Adams DJ, Beveridge DJ, van der Weyden L, Mangs H, Leedman PJ, Morris BJ (Nov 2003). "HADHB, HuR, and CP1 bind to the distal 3'-untranslated region of human renin mRNA and differentially modulate renin expression". The Journal of Biological Chemistry 278 (45): 44894–903. doi:10.1074/jbc.M307782200. PMID 12933794.
  9. ↑ Hobart PM, Fogliano M, O'Connor BA, Schaefer IM, Chirgwin JM (Aug 1984). "Human renin gene: structure and sequence analysis". Proceedings of the National Academy of Sciences of the United States of America 81 (16): 5026–30. doi:10.1073/pnas.81.16.5026. PMC 391630. PMID 6089171.
  10. ↑ "Non-Invasive Blood Pressure data for Ren1". Wellcome Trust Sanger Institute.
  11. ↑ "Salmonella infection data for Ren1". Wellcome Trust Sanger Institute.
  12. ↑ "Citrobacter infection data for Ren1". Wellcome Trust Sanger Institute.
  13. ↑ 13.0 13.1 13.2 Gerdin, A. K. (2010). "The Sanger Mouse Genetics Programme: High throughput characterisation of knockout mice". Acta Ophthalmologica 88: 925–7. doi:10.1111/j.1755-3768.2010.4142.x.
  14. ↑ Mouse Resources Portal, Wellcome Trust Sanger Institute.
  15. ↑ 15.0 15.1 Adams DJ, Head GA, Markus MA, Lovicu FJ, van der Weyden L, Köntgen F et al. (Oct 2006). "Renin enhancer is critical for control of renin gene expression and cardiovascular function". The Journal of Biological Chemistry 281 (42): 31753–61. doi:10.1074/jbc.M605720200. PMID 16895910.
  16. ↑ van der Weyden L, White JK, Adams DJ, Logan DW (2011). "The mouse genetics toolkit: revealing function and mechanism". Genome Biology 12 (6): 224. doi:10.1186/gb-2011-12-6-224. PMC 3218837. PMID 21722353.
  17. ↑ Presentation on Direct Renin Inhibitors as Antihypertensive Drugs
  18. ↑ Ram CV (Sep 2009). "Direct inhibition of renin: a physiological approach to treat hypertension and cardiovascular disease". Future Cardiology 5 (5): 453–65. doi:10.2217/fca.09.31. PMID 19715410.
  19. ↑ Méndez GP, Klock C, Nosé V (Feb 2011). "Juxtaglomerular cell tumor of the kidney: case report and differential diagnosis with emphasis on pathologic and cytopathologic features". International Journal of Surgical Pathology 19 (1): 93–8. doi:10.1177/1066896908329413. PMID 19098017.
  20. ↑ Hamilton Regional Laboratory Medicine Program - Laboratory Reference Centre Manual. Renin Direct.
  21. ↑ Phillips MI, Schmidt-Ott KM (Dec 1999). "The Discovery of Renin 100 Years Ago". News in Physiological Sciences 14: 271–274. PMID 11390864.
  22. ↑ Tigerstedt R, Bergman PG (1898). "Niere und Kreislauf" [Scandinavian Archives of Physiology]. Skandinavisches Archiv für Physiologie (in German) 8: 223–271. doi:10.1111/j.1748-1716.1898.tb00272.x.

External links