Unique form and osmoregulatory function of a neurohypophysial hormone in a urochordate.
ABSTRACT The cyclic nonapeptides, oxytocin and vasopressin, are neurohypophysial hormones that regulate many significant physiological processes related especially to reproduction and osmoregulation. In this study, we characterized an oxytocin-related peptide cDNA from a urochordate, Styela plicata, thought to be a sister group to vertebrates. Sequence analysis of the deduced precursor polypeptide revealed that the precursor is composed of three segments: a signal peptide, an oxytocin-like sequence flanked by a Gly C-terminal amidation signal and a Lys-Arg dibasic processing site, and a neurophysin domain, similar to other oxytocin/vasopressin family precursors. However, unlike other members of this family, the tunicate oxytocin-like peptide (CYISDCPNSRFWST-NH2) is a tetradecapeptide. We termed this peptide Styela oxytocin-related peptide (SOP). Furthermore, analyses of mass spectrometry, in situ hybridization, and immunohistochemistry demonstrated production of mature SOP in the cerebral ganglion. To elucidate the physiological action of SOP, we kept the tunicate for 2 d under the three different concentrations of seawater, 60, 100, and 130%, and measured the expression levels of SOP mRNA in the cerebral ganglion. The greatest expression of SOP mRNA was observed in the 60% seawater. In 60% seawater, but not in 100 or 130%, the tunicate mostly closed the atrial and branchial siphons. Therefore, we investigated the contractile effects of SOP on the siphons in vitro. SOP caused contractions in both siphons in a dose-dependent manner. Taken together, these results suggest that SOP acts to prevent the influx of a low concentration of seawater into the body and thus play an important role in osmoregulation.
Article: Characterization of the neurohypophysial hormone gene loci in elephant shark and the Japanese lamprey: origin of the vertebrate neurohypophysial hormone genes.[show abstract] [hide abstract]
ABSTRACT: Vasopressin and oxytocin are mammalian neurohypophysial hormones with distinct functions. Vasopressin is involved mainly in osmoregulation and oxytocin is involved primarily in parturition and lactation. Jawed vertebrates contain at least one homolog each of vasopressin and oxytocin, whereas only a vasopressin-family hormone, vasotocin, has been identified in jawless vertebrates. The genes encoding vasopressin and oxytocin are closely linked tail-to-tail in eutherian mammals whereas their homologs in chicken, Xenopus and coelacanth (vasotocin and mesotocin) are linked tail-to-head. In contrast, their pufferfish homologs, vasotocin and isotocin, are located on the same strand of DNA with isotocin located upstream of vasotocin and separated by five genes. These differences in the arrangement of the two genes in different bony vertebrate lineages raise questions about their origin and ancestral arrangement. To trace the origin of these genes, we have sequenced BAC clones from the neurohypophysial gene loci in a cartilaginous fish, the elephant shark (Callorhinchus milii), and in a jawless vertebrate, the Japanese lamprey (Lethenteron japonicum). We have also analyzed the neurohypophysial hormone gene locus in an invertebrate chordate, the amphioxus (Branchiostoma floridae). The elephant shark neurohypophysial hormone genes encode vasotocin and oxytocin, and are linked tail-to-head like their homologs in coelacanth and non-eutherian tetrapods. Besides the hypothalamus, the two genes are also expressed in the ovary. In addition, the vasotocin gene is expressed in the kidney, rectal gland and intestine. These expression profiles indicate a paracrine role for the two hormones. The lamprey locus contains a single neurohypophysial hormone gene, the vasotocin. The synteny of genes in the lamprey locus is conserved in elephant shark, coelacanth and tetrapods but disrupted in teleost fishes. The amphioxus locus encodes a single neurohypophysial hormone, designated as [Ile4]vasotocin. The vasopressin- and oxytocin-family of neurohypophysial hormones evolved in a common ancestor of jawed vertebrates through tandem duplication of the ancestral vasotocin gene. The duplicated genes were linked tail-to-head like their homologs in elephant shark, coelacanth and non-eutherian tetrapods. In contrast to the conserved linkage of the neurohypophysial genes in these vertebrates, the neurohypophysial hormone gene locus has experienced extensive rearrangements in the teleost lineage.BMC Evolutionary Biology 03/2009; 9:47. · 3.52 Impact Factor
[show abstract] [hide abstract]
ABSTRACT: The neuropeptide S receptor (NPSR) is a recently deorphanized member of the G protein-coupled receptor (GPCR) superfamily and is activated by the neuropeptide S (NPS). NPSR and NPS are widely expressed in central nervous system and are known to have crucial roles in asthma pathogenesis, locomotor activity, wakefulness, anxiety and food intake. The NPS-NPSR system was previously thought to have first evolved in the tetrapods. Here we examine the origin and the molecular evolution of the NPSR using in-silico comparative analyses and document the molecular basis of divergence of the NPSR from its closest vertebrate paralogs. In this study, NPSR-like sequences have been identified in a hemichordate and a cephalochordate, suggesting an earlier emergence of a NPSR-like sequence in the metazoan lineage. Phylogenetic analyses revealed that the NPSR is most closely related to the invertebrate cardioacceleratory peptide receptor (CCAPR) and the group of vasopressin-like receptors. Gene structure features were congruent with the phylogenetic clustering and supported the orthology of NPSR to the invertebrate NPSR-like and CCAPR. A site-specific analysis between the vertebrate NPSR and the well studied paralogous vasopressin-like receptor subtypes revealed several putative amino acid sites that may account for the observed functional divergence between them. The data can facilitate experimental studies aiming at deciphering the common features as well as those related to ligand binding and signal transduction processes specific to the NPSR.PLoS ONE 01/2012; 7(3):e34046. · 4.09 Impact Factor