Expression of Tick Receptor Protein in Xenopus laevis Oocyte

Mature Xenopus oocytes have diameters of 1 to 1.2mm. They are surrounded by a noncellular, fibrous vitelline layer and by several layers of follicular cells ( Dumont et al., 1978) Fig. 1. Xenopus oocytes have been extensively used to study biogenesis, functional architecture, and modulation of plasma membrane expression of mRNAs encoding membrane receptors or ion channels. In 1971, Gurdon et al. reported that Xenopus oocytes translate foreign mRNA. Xenopus oocytes are capable of translation and post-translational modification (Ghysdael et al., 1977), phosphorylation (Gedamu et al., 1978) and glycosylation (Colman et al., 1981; Lund et al., 1986). A Xenopus oocyte can also assemble the subunits of a receptor and insert them into its surface membrane (Parker et al., 1985) Sumikawa et al. (1981) demonstrated the presence of binding sites for a-bungarotoxin when oocytes were injected with mRNA from the electric organ of Torpedo marmorata. Barnard et al. (1982) presented the first electrophysiological evidence for the expression of functional nAChR in Xenopus oocytes. Expressed protein can be detected as long as two weeks after RNA injection (Lerma et al., 1988). The Xenopus oocyte technique has been extended to examine the properties of other receptors . Gunderson et al. (1983,1984,1986); Miledi et al. (1982); Sumikawa (1984); Parker et al. (1984,1986) and, Sholfield et al. (1987) reported the successful expression of serotonin, dopamine, GABA and glycine receptors. Saito et al. (1987) reported for the first time that Xenopus oocytes successfully express glutamate receptors from lobster (Palinurus japonicus ) abdominal muscle. L-glutamate responses in oocytes injected with lobster muscle RNA have been also reported by Kawai et al. (1989). Fraser et al. (1990) published that amino acid receptors expressed in Xenopus oocyte after " microinjection of mRNA from the leg of locust Schistocerca gregaria. Marshal et al. (1990) found the complete sequence of a locust (Schistocerca gregaria) nervous system nAChR subunit (alpha-L1). RNA derived from alpha-L1 cDNA when injected alone in Xenopus oocyte resulted in the expression of functional nAChR. Arena et al. (1991) recently reported that C. elegans poly A+ RNA injected into Xenopus oocytes expresses L-glutamate-sensitive chloride channels.