D. Barsyte et al., Rainbow trout (Oncorhynchus mykiss) urotensin-I: Structural differences between urotensins-I and urocortins, GEN C ENDOC, 115(2), 1999, pp. 169-177
In bony fishes, both corticotropin-releasing factor (CRF) and urotensin-I p
lay a role in the regulation of interrenal glucocorticoid release. The rain
bow trout, Oncorhynchus mykiss,:is a useful model for understanding the mec
hanisms of stress and the hypothalamo-pituitary-interrenal axis because of
its phylogenetic position at the base of the euteleostei and its popularity
as a food fish. Urotensin-I may act as a glucocorticoid releaser in a mech
anism phylogenetically older than that of CRE The structural and functional
relationships of trout urotensin-I have been investigated. The transcript
was cloned from a trout brain hypothalamic cDNA library. A single positive
clone was isolated and sequenced. It possesses 3218 bases and has the longe
st 3' untranslated region of all urotensins-I and CRF transcripts found to
date. In comparison to the other fish orthologues, it has the closest seque
nce identity to the mammalian urocortins. The transcript appears to be diff
erentially processed in brain and urophysis as determined by Northern blot
analysis and the presence of polyadenylation signals in the 3' untranslated
region. Synthetic trout urotensin-I activated both human CRF-R1 and -R2 re
ceptor-transfected CHO cells with a potency similar to that of white sucker
(Catostomus commersoni) urotensin-I. Both fish neuropeptides possessed an
order of magnitude less potency than human urocortin in CRF-R2 transfected
cells. (C) 1999 Academic Press.