relaxin

For the Miles Davis album, see Relaxin' with the Miles Davis Quintet.

Relaxin 1 Identifiers Symbol RLN1 Alt. symbols H1 Entrez 6013 HUGO 10026 OMIM 179730 RefSeq NM_006911 UniProt P04808 Other data Locus Chr. 9 qter-q12

Relaxin 2 Identifiers Symbol RLN2 Alt. symbols H2, RLXH2, bA12D24.1.1, bA12D24.1.2 Entrez 6019 HUGO 10027 OMIM 179740 PDB 6RLX RefSeq NM_134441 UniProt P04090 Other data Locus Chr. 9 qter-q12

Relaxin 3 Identifiers Symbol RLN3 Alt. symbols ZINS4, RXN3, H3 Entrez 117579 HUGO 17135 OMIM 606855 RefSeq NM_080864 UniProt Q8WXF3 Other data Locus Chr. 19 p13.3

Relaxin is a peptide hormone that was first described in 1926 by Frederick Hisaw.^[1][2]

The relaxin-like peptide family belongs in the insulin superfamily and consists of 7 peptides of high structural but low sequence similarity; relaxin-1 (RNL1), 2 (RNL2) and 3( RNL3), and the insulin-like (INSL) peptides, INSL3, INSL4, INSL5 and INSL6. The functions of relaxin-3, INSL4, INSL5, INSL6 remain uncharacterised.^[3]

Synthesis

In the female, it is produced by the corpus luteum of the ovary, the breast and, during pregnancy, also by the placenta, chorion, and decidua.

In the male it is produced in the prostate and is present in human semen.^[4]

Structure

Structurally, relaxin is a heterodimer of two peptide chains of 24 and 29 amino acids that are linked by disulfide bridges and it appears related to insulin.

Relaxin is produced from its prohormone, “pro-relaxin”, by splitting off one additional peptide chain.

Function

Enhances motility of sperm in semen.^[5]

In humans

Relaxin is produced mainly by the corpus luteum, in both pregnant and non-pregnant females, it rises to a peak within approximately 14 days of ovulation and then declines in the absence of pregnancy resulting in menstruation. During the first trimester of pregnancy levels rise and additional relaxin is produced by the decidua.

Relaxin's role or necessity in human pregnancy remains under investigation, as in humans its peak is reached during the 14 weeks of the first trimester and at delivery. It is believed to soften pubic symphysis.

In non-human animals

In animals relaxin widens the pubic bone and facilitates labor, it also softens the cervix (cervical ripening), and relaxes the uterine musculature. Thus, for a long time, relaxin was looked at as a pregnancy hormone. However, its significance may reach much further. Relaxin affects collagen metabolism, inhibiting collagen synthesis and enhancing its breakdown by increasing matrix metalloproteinases.^[6] It also enhances angiogenesis and is a potent renal vasodilator.

Receptors

Relaxin interacts with the relaxin receptor LGR7 (RXFP1) and LGR8 (RXFP2) which belong to the G-protein-coupled receptor superfamily. They contain a heptahelical transmembrane domain and a large glycosylated ectodomain, distantly related to the receptors for the glycoproteohormones, such as the LH-receptor or FSH-receptor.

Relaxin receptors have been found in the heart, smooth muscle, the connective tissue, and central and autonomous nervous system.

Disorders

Specific disorders related to relaxin have not been described, yet it has been suggested that it could be linked to scleroderma and to fibromyalgia.^[7]

References

External links

• MeSH Relaxin
• "Relaxin". Human Protein Reference Database. Johns Hopkins University and the Institute of Bioinformatics. http://www.hprd.org/resultsQuery?multiplefound=&prot_name=Relaxin&external=Ref_seq&accession_id=&hprd=&gene_symbol=&chromo_locus=&function=&ptm_type=&localization=&domain=&motif=&expression=&prot_start=&prot_end=&limit=0&mole_start=&mole_end=&disease=&query_submit=Search. Retrieved 2009-05-20.