Molecular characterization and analysis of a truncated serotonin receptor gene expressed in neural and reproductive tissues of abalone.
In molluscs, the neurotransmitter serotonin (5-HT) has been linked to a variety of biological roles including gamete maturation and spawning. The possible involvement of 5-HT in abalone gamete release was demonstrated by a dose-dependent increase in Haliotis rubra gonad contractile bioactivity following 5-HT stimulation. Physiological functions associated with 5-HT, are mediated through binding to 5-HT receptors. A cDNA encoding a putative 5-HT receptor consisting of 359 amino acids was isolated from the tropical abalone H. asinina, termed 5-HT(1 ha). The 5-HT(1 ha) shares G-protein-coupled receptor motifs with metazoan 5-HT receptors, including predicted transmembrane domains, active sites for protein kinase action, and N-linked glycosylation sites. However, the third intracellular loop of 5-HT(1 ha) is relatively short, and only six transmembrane domains are predicted, implying a truncated receptor. Phylogenetic analysis with known 5-HT receptor genes suggests that 5-HT(1 ha) belongs to the type 1 5-HT receptor family. Expression analysis by RT-PCR showed that 5-HT(1 ha) mRNA was present in all tissues examined, including the neural ganglia and gonad tissues. Immunocytochemistry revealed the presence of 5-HT(1 ha) specifically within the soma of neuronal cells located in the outer cortex of both cerebral and pleuropedal ganglia. In ovarian and testicular tissues, 5-HT(1 ha) immunoreactivity was observed in epithelial cells of the outer capsule and connective tissue of the trabeculae to which the gamete follicles adhere. Whether this receptor transcript is translated to a functional protein needs to be verified, but if so, it could play a role in reproduction.
Panasophonkul
Sasiporn
S
Department of Anatomy, Faculty of Science, Mahidol University, Bangkok, 10400, Thailand.
Apisawetakan
Somjai
S
Cummins
Scott F
SF
York
Patrick S
PS
Degnan
Bernard M
BM
Hanna
Peter J
PJ
Saitongdee
Porncharn
P
Sobhon
Prasert
P
Sretarugsa
Prapee
P
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005260:Female; D017952:Ganglia, Invertebrate / Q000378:metabolism*; D049851:Gastropoda / Q000378:metabolism*; D015870:Gene Expression; D006066:Gonads / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D010802:Phylogeny; D044282:Receptor, Serotonin, 5-HT1A / Q000235:genetics*; D016415:Sequence Alignment
D044282:Receptor, Serotonin, 5-HT1A