Prostanoid receptors (PG-Rs: prostaglandin D, E, F, prostacyclin and
thromboxane receptors (DP, EP1-4, FP, IP and TP)) are known to mediate a diverse
range of biological responses, such as cardiovascular homeostasis, nociception and
reproduction, via binding to their respective ligands belonging to the five classes of
prostanoids (PGs: class D, E, F, I and thromboxane). The majority of these findings
were reported in mammals, and despite suggestive evidence provided by previous
pharmacological and physiological studies in non-mammalian vertebrates,
investigations on the mechanisms behind actions of PGs were impeded by the limited
information on their receptors.
In the present study, the full-length cDNAs of chicken (c-) and zebrafish
(z-) prostanoid receptors – cEP3, cFPs, zEP1s and zFP – were identified from
respective adult ovaries and their tissue distribution examined by RT-PCR. A novel
middle-truncated splice variant, cFPb, which lacks 107 amino acids between
transmembrane domains 4 and 6 but otherwise identical to cFPa was first identified.
Three isoforms of zEP1 – zEP1a, zEP1b, zEP1c – were found, which might have subfunctionalized
in their ligand binding and G protein coupling specificity, in addition to
differential tissue distribution. Using various luciferase reporter systems (pGL3-CRE,
pGL-NFAT-RE, pGL4-SRE), all the cloned receptors, except cFPb, were shown to
potentially couple to intracellular cAMP, Ca2+, and/or MAPK signaling pathways.
Owing to the proposed roles of PGs and its potential regulation by and/or
on EGFR ligands and gonadotropins in mammals and chicken, genes involved in
regulation of PG functions at various levels, including biosynthesis (COX1, COX2,
mPGES1, mPGES2 and cPGES), availability (PGT) and signaling (cEPs and cFPs),
were also characterized in granulosa cells during hen follicular development.
Lastly, using our experimental data and systematic sequence retrieval
from available databases, the PG receptor cascades from representative vertebrate
species were pooled and analysed using phylogenetic analyses and synteny studies.
Three putative clusters (IP-like, EP4-like and EP1-like cluster) were found in lamprey
genome; meanwhile, only one PG-R-like cluster was identified from the
Cephalochordate lancelet (amphioxus) genome. This concurs with the 1-2-4 rule
proposed in first round/second round (1R/2R) whole genome duplication in which the
missing lamprey cluster was presumably lost secondarily. With support from
conserved orthologs-localization, the four PG-R paralogs (proto-EP4, proto-IP/EP2/DP,
proto-TP/FP/EP1 & putative proto-EP3 genes) in the ancestral vertebrates might have
further diversified via either localized- (e.g. EP2 and DP) or chromosomal segmental
duplication (e.g. EP1, FP and TP) which resulted in the present array of vertebrate PGRs.
Additional paralogs (e.g. EP1 and EP4) were identified from fishes, by which
molecular dating coincide with and hint of their origins whence the ancient fishspecific
whole genome duplication (3R) occurred ~350 million years ago.
The present study offers the first glimpse and a better understanding of the
roles of the PG-Rs and presents a higher resolution to the evolutionary history of each
PG-R family member, consolidating that particular care has to be taken when studying
non-mammalian PG-R functions in which some members are absent or present in
multiples and propel the investigation of adaptational changes in the coding sequence
during evolution of vertebrate PG-Rs. / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy
| Identifer | oai:union.ndltd.org:HKU/oai:hub.hku.hk:10722/181300 |
| Date | January 2011 |
| Creators | Kwok, Ho-yan, Amy., 郭可茵. |
| Publisher | The University of Hong Kong (Pokfulam, Hong Kong) |
| Source Sets | Hong Kong University Theses |
| Language | English |
| Detected Language | English |
| Type | PG_Thesis |
| Source | http://hub.hku.hk/bib/B47752609 |
| Rights | The author retains all proprietary rights, (such as patent rights) and the right to use in future works., Creative Commons: Attribution 3.0 Hong Kong License |
| Relation | HKU Theses Online (HKUTO) |
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