Human Relaxin Gene 3 (H3) and the Equivalent Mouse Relaxin (M3) Gene

Abstract

We have identified a novel human relaxin gene, designated H3 relaxin, and an equivalent relaxin gene in the mouse from the Celera Genomics data base. Both genes encode a putative prohormone sequence incorporating the classic two-chain, three cysteine-bonded structure of the relaxin/insulin family and, importantly, contain the RXXXRXX(I/V) motif in the B-chain that is essential for relaxin receptor binding. A peptide derived from the likely proteolytic processing of the H3 relaxin prohormone sequence was synthesized and found to possess relaxin activity in bioassays utilizing the human monocytic cell line, THP-1, that expresses the relaxin receptor. The expression of this novel relaxin gene was studied in mouse tissues using RT-PCR, where transcripts were identified with a pattern of expression distinct from that of the previously characterized mouse relaxin. The highest levels of expression were found in the brain, whereas significant expression was also observed in the spleen, thymus, lung, and ovary. Northern blotting demonstrated an ϳ1.2-kb transcript present in mouse brain poly(A) RNA but not in other tissues. These data, together with the localization of transcripts in the pars ventromedialis of the dorsal tegmental nucleus of C57BLK6J mouse brain by in situ hybridization histochemistry, suggest a new role for relaxin in neuropeptide signaling processes. Together, these studies describe a third member of the human relaxin family and its equivalent in the mouse.Relaxin is a 6-kDa polypeptide hormone that is secreted by the ovary into the peripheral circulation in highest amounts during pregnancy and has a number of functions in mammals that are generally associated with female reproductive tract physiology (1). To date, only one relaxin gene has been characterized in most mammalian species, with the exception of the human where two separate genes have been described, designated H1 (2) and H2 (3) relaxin. The peptide encoded by the H2 gene is the major stored and circulating form in the human (4). H1 relaxin expression is restricted to the decidua, placenta, and prostate (5); however, the H1 peptide has similar biological activity to that of H2 relaxin in a rat atrial bioassay (6). The actions of relaxin include an ability to inhibit myometrial contractions, to stimulate remodeling of the connective tissue, and to induce softening of the tissues of the birth canal. Additionally, relaxin increases growth and differentiation of the mammary gland and nipple and induces the breakdown of collagen, one of the main components of connective tissue. Relaxin decreases collagen synthesis and increases the release of collagenases (7). These findings were recently confirmed by the establishment of the relaxin gene-knockout mouse (8), which exhibited a number of phenotypic properties associated with pregnancy. Female mice lacking a functionally active relaxin gene failed to relax and elongate the interpubic ligament of the pubic symphysis and could not suckle their pups, who in turn died within 24 h unless cross-fostered t...

H2 relaxin overexpression increases in vivo prostate xenograft tumor growth and angiogenesis

“…12,13 Of the 3 relaxin peptides, H2 relaxin remains the most widely studied for several reasons: 1) the availability of specific H2 relaxin antibodies 8 , 2) the significance and characterized profile of circulating H2 relaxin during pregnancy 8 and 3) the understanding that H2 relaxin retains the greatest bioactivity compared to H1 and H3. [12][13][14] PC-3 and LNCaP human prostate cancer cell lines have been employed to investigate differential H1 and H2 relaxin gene regulation, expression and transcript half-life. 12,15,16 It appears that although H1 relaxin has a greater half-life (3.17 days) compared to H2 relaxin (11.4 hours), H2 relaxin possesses stronger promoter regulation leading to greater mRNA levels and possibly higher peptide concentration.…”

“…While H2 and H3 relaxins are expressed in a number of tissues, in males their predominant expression is found in the prostate and brain, respectively. 12,13 Of the 3 relaxin peptides, H2 relaxin remains the most widely studied for several reasons: 1) the availability of specific H2 relaxin antibodies 8 , 2) the significance and characterized profile of circulating H2 relaxin during pregnancy 8 and 3) the understanding that H2 relaxin retains the greatest bioactivity compared to H1 and H3. [12][13][14] PC-3 and LNCaP human prostate cancer cell lines have been employed to investigate differential H1 and H2 relaxin gene regulation, expression and transcript half-life.…”

Effects of acute and chronic relaxin-3 on food intake and energy expenditure in rats

“…Like insulin, the intervening C peptide chain of relaxin-3 is removed by proteolytic processing. The relaxin-3 gene has been identified in humans (H3) [2], mice (M3) [2] and rats (R3) [3], and the gene products are highly homologous. R3 and M3 mRNA expression is localized to the nucleus incertus (NI) of the brainstem [3], a small nucleus in the central gray of the median dorsal pons near the fourth ventricle with projections to many hypothalamic nuclei.…”

SNP analysis, genotyping and mapping of the porcine <i>GPCR142</i> gene (Brief report)

“…Pharmacological studies of the GPCR142 gene indicated that the RLN3 gene is the only member of the RLN family showing the ability to activate this gene (BATHGATE et al, 2002). The GPCR142 gene contains a single exon and is located on chromosome 1 (1q22) in human (FREDRIKSSON et al, 2003).…”

“…Background: The RLN3 gene has been recently reported as a ligand for two related orphan G protein-coupled receptors, GPCR135 and GPCR142 (BATHGATE et al, 2002;LIU et al, 2003a;LIU et al, 2003b;CHEN et al, 2005). Pharmacological studies of the GPCR142 gene indicated that the RLN3 gene is the only member of the RLN family showing the ability to activate this gene (BATHGATE et al, 2002).…”