Tachykinin and tachykinin receptor of an ascidian, Ciona intestinalis: evolutionary origin of the vertebrate tachykinin family.
Tachykinins (TKs) are the most prevalent vertebrate brain/gut peptides. In this study, we originally identified authentic TKs and their receptor from a protochordate, Ciona intestinalis. The Ciona TK (Ci-TK) precursor, like mammalian gamma-preprotachykinin A (gamma-PPTA), encodes two TKs, Ci-TK-I and -II, including the -FXGLM-NH(2) vertebrate TK consensus. Mass spectrometry of the neural extract revealed the production of both Ci-TKs. Ci-TK-I contains several Substance P (SP)-typical amino acids, whereas a Thr is exceptionally located at position 4 from the C terminus of Ci-TK-II. The Ci-TK gene encodes both Ci-TKs in the same exon, indicating no alternative generation of Ci-TKs, unlike the PPTA gene. These results suggested that the alternative splicing of the PPTA gene was established during evolution of vertebrates. The only Ci-TK receptor, Ci-TK-R, was equivalently activated by Ci-TK-I, SP, and neurokinin A at physiological concentrations, whereas Ci-TK-II showed 100-fold less potent activity, indicating that the ligand selectivity of Ci-TK-R is distinct from those of vertebrate TK receptors. Ci-TK-I, like SP, also elicited the typical contraction on the guinea pig ileum. The Ci-TK gene was expressed in neurons of the brain ganglion, small cells in the intestine, and the zone 7 in the endostyle, which corresponds to the vertebrate thyroid gland. Furthermore, the Ci-TK-R mRNA was distributed in these three tissues plus the gonad. These results showed that Ci-TKs play major roles in sexual behavior and feeding in protochordates as brain/gut peptides and endocrine/paracrine molecules. Taken together, our data revealed the biochemical and structural origins of vertebrate TKs and their receptors.
Satake
Honoo
H
Suntory Institute for Bioorganic Research, Wakayamadai 1-1-1, Shimamoto-cho, Mishima-gun, Osaka 618-8503, Japan. satake@sunbor.or.jp
Ogasawara
Michio
M
Kawada
Tsuyoshi
T
Masuda
Katsuyoshi
K
Aoyama
Masato
M
Minakata
Hiroyuki
H
Chiba
Takuto
T
Metoki
Hitoe
H
Satou
Yutaka
Y
Satoh
Nori
N
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D015139:Blotting, Southern; D001921:Brain / Q000378:metabolism; D002938:Ciona intestinalis / Q000235:genetics*; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005091:Exons; D005724:Ganglia / Q000473:pathology; D006168:Guinea Pigs; D007082:Ileum / Q000378:metabolism; D017403:In Situ Hybridization; D007413:Intestinal Mucosa / Q000378:metabolism; D007477:Ions; D008024:Ligands; D013058:Mass Spectrometry; D008969:Molecular Sequence Data; D015288:Neurokinin A / Q000378:metabolism; D009865:Oocytes / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D016133:Polymerase Chain Reaction; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D018039:Receptors, Tachykinin / Q000235:genetics* / Q000502:physiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D015320:Tachykinins / Q000235:genetics* / Q000502:physiology; D013961:Thyroid Gland / Q000378:metabolism; D014981:Xenopus
D018076:DNA, Complementary; D007477:Ions; D008024:Ligands; D010455:Peptides; D012333:RNA, Messenger; D018039:Receptors, Tachykinin; D015320:Tachykinins; D015288:Neurokinin A