CFTR PROTEIN IS INVOLVED IN THE EFFLUX OF NEUTRAL AMINO-ACIDS

Trans-membrane fluxes of leucine were measured in mouse C127i cells tr ansfected with the wild type (C127 CFTRw/t) or the Delta F508 CF gene (C127 CFTR Delta F508). Leucine efflux was significantly faster in C12 7 CFTRw/t cells. On the contrary, leucine influx was comparable in the two cell lines and referable to a ''L-type'' transport system. No sig nificant differences in leucine content were detected among the two ce ll lines when maintained in complete growth medium; in contrast, after prolonged incubation in amino-acid-free saline solution, the amount o f intracellular leucine was significantly smaller in C127 CFTRw/t than in C127 CFTR Delta F508 cells. Leucine behavior was shared by other n eutral amino acids with non polar side chains. These results suggest t hat the expression of normal CFTR increases the efflux of a subgroup o f neutral amino acids. (C) 1994 Academic Press, Inc.