Confocal microscopic study of GABAA receptors in Xenopus oocytes after mRNA injecton: modulation by tyrosine kinase activity

The expression of GABAA receptors in Xenopus oocytes injected with rat brain mRNA was studied by immunocytochemistry and evaluation of the distribution of fluorescent probes at the confocal microscope. The beta (2/3) subunit distributed exclusively on the membrane at the animal pole of the oocytes. Treatment of oocytes for 20 min with the protein tyrosine kinase inhibitor genistein, 200 muM, resulted in a lower presence of GABA(A) receptors on the membrane. The inactive genistein analogue daidzein, 200 muM, had no effect even with a 30 min treatment. Alkaline phosphatase but not a protein tyrosine phosphatase, when injected into oocytes, reduced GABA receptor membrane expression. The data indicate that protein tyrosine phosphorylation modulates the expression on the plasma membrane of presynthesized GABAA receptors