Early Expression of a Novel Nucleotide Receptor in the Neural Plate of Xenopus Embryos*

Extracellular ATP functions as a neurotransmitter and neuromodulator in the adult nervous system, and a signaling molecule in non-neural tissue, acting either via ligand-gated ion channels (P2X) or G-protein-coupled receptors (P2Y). ATP can cause an increase in intracellular Ca²⁺(Ca²⁺_i) in embryonic cells and so regulate cell proliferation, migration, and differentiation. We have isolated aXenopus cDNA encoding a novel P2Y receptor, XlP2Y, which is expressed abundantly in developing embryos. Recombinant XlP2Y responds equally to all five naturally occurring nucleoside triphosphates (ATP, UTP, CTP, GTP, and ITP), which elicit a biphasic Ca²⁺-dependent Cl⁻ current (I _Cl,Ca) where the second phase persists for up to 60 min. XlP2Y also causes a continuous release of Ca²⁺_i and a low level persistent activation ofI _Cl,Ca in Xenopus oocytes through the spontaneous efflux of ATP. mRNAs for XlP2Y are expressed transiently in the neural plate and tailbud during Xenopusdevelopment, coincident with neurogenesis. This restricted pattern of expression and novel pharmacological features confer unique properties to XlP2Y, which may play a key role in the early development of neural tissue.