Molecular cloning and functional expression of the Penaeus monodon 5-HT receptor

Serotonin (5-HT) mediates a number of diverse physiological functions in crustaceans by interacting with various 5-HT receptor subtypes. A putative 5-HT receptor cloned from the ovary of the black tiger prawn (Penaeus monodon) consisted of 2291 nucleotides, encoding a putative 5-HT1Pem receptor protein of 591 amino acids. Transient expression of 5-HT1Pem in HEK293 cells demonstrated a saturable [3H]-5-HT binding with a Kd of 10.43 ± 1.13 nM and Bmax of 1.53 ± 0.06 pmol/mg. The putative 5-HT1Pem receptor is expressed in all tissues examined and is constitutively expressed in the ovary during ovarian maturation and spent phase. Polyclonal antibodies against the third intracellular loop (i3 loop) of the 5-HT receptor showed that the 5-HT1Pem receptor protein was expressed in the trabeculae of ovarian stages 1 and 2 but on the cortical rod and surrounding the oocyte membrane of stages 3 and 4, suggesting that receptor localization plays a critical role in regulating ovarian maturation and spawning in penaeus shrimp.