UII and UT in grouper: cloning and effects on the transcription of hormones related to growth control

Abstract

Urotensin II (UII) is a cyclic peptide that was originally extracted from the caudal neurosecretory system (CNSS) of fish. UII is well known to exhibit cardiovascular, ventilatory, and motor effects in vertebrates. Studies have reported that UII exerts mitogenic effects and can act as an autocrine/paracrine growth factor in mammals. However, similar information in fish is limited. In this study, the full-length cDNAs of UII and its receptor (UT) were cloned and characterized in the orange-spotted grouper. UII and UT were expressed ubiquitously in various tissues in grouper, and particularly high levels were observed in the CNSS, CNS, and ovary. A functional study showed that UT was coupled with intracellular Ca 2C mobilization in HEK293 cells. Studies carried out using i.p. injections of UII in grouper showed the following: i) in the hypothalamus, UII can significantly stimulate the mRNA expression of ghrh and simultaneously inhibit the mRNA expression of somatostatin 1 (ss1) and ss2 3 h after injection; ii) in the pituitary, UII also significantly induced the mRNA expression of gh 6 and 12 h after injection; and iii) in the liver, the mRNA expression levels of ghr1/ghr2 and igf1/igf2 were markedly increased 12 and 3 h after the i.p. injection of UII respectively. These results collectively indicate that the UII/UT system may play a role in the promotion of the growth of the orange-spotted grouper.

International Union of Basic and Clinical Pharmacology. XCII. Urotensin II, Urotensin II–Related Peptide, and Their Receptor: From Structure to Function

“…Immunohistochemical labeling has confirmed that UII is primarily located in neurosecretory cells of the ventral spinal cord (Owada et al, 1985;Oka et al, 1989;Parmentier et al, 2006). However, subsequent studies have shown that UII is also present in the fish brain (Waugh and Conlon, 1993), and the expression of UII mRNA in fish brain has been confirmed by reverse-transcription polymerase chain reaction (RT-PCR; Lu et al, 2006;Sun et al, 2014). In various species of freshwater and seawater fish, UII is found in cerebrospinal fluid (CSF)-contacting neurons located within the ventral ependyma bordering the central canal along the entire length of the spinal cord and medulla Lederis 1986, 1988).…”

“…The 222 UII gene is also expressed in flounder and grouper endocrine glands, including pituitary, head kidney (where the interrenal tissue is located), and ovary (Lu et al, 2006;Sun et al, 2014).…”

“…In the anterior horn of the spinal cord, intense expression of UT is observed in motor neurons (Liu et al, 1999;Sun et al, 2014).…”

“…In the flounder and the orange-spotted grouper Epinephelus coioides, UT transcripts are also present in all regions of the brain including the forebrain, midbrain, hypothalamus, and hindbrain (Lu et al, 2006;Sun et al, 2014).…”

MOLECULAR EVOLUTION OF GPCRS: Somatostatin/urotensin II receptors

“…Double-immunofluorescence labeling in mouse brain revealed a co-localization of URP and GNRH in fibers in the median eminence and vascular organ of the lamina terminalis as well as in cell bodies in the preoptic area, suggesting that URP is co-released with GNRH (Egginger et al 2011). In the orange-spotted grouper (Epinephelus coioides), UII may promote growth through the activation of GHRH expression and inhibition of SS1 and SS2 concentrations in the hypothalamus, which stimulates GH expression in the pituitary and increases GH receptor expression (Sun et al 2013).…”