?Ammonium-induced internalisation of UapC, the general purine permease from Aspergillus nidulans

VALDEZ TAUBAS, J; HARISPE, L; SCAZZOCCHIO C; GORFINKIEL L; ROSA AL

FUNGAL GENETICS AND BIOLOGY

Año: 2004 vol. 41 p. 42 - 51

1087-1845

The Aspergillus nidulans UapC protein is a high-affinity, moderate-capacity, uric acid?xanthine transporter, which also displays a low transport capacity for hypoxanthine, adenine, and guanine. It has been previously shown that a functional UapC?GFP fusion protein localises at the plasma membrane [Fungal Genet. Biol. 30 (2000) 105]. Here, we demonstrate that ammonium, a preferred nitrogen source, dramatically changes the subcellular distribution of UapC. After addition of ammonium, UapC?GFP is removed from the plasma membrane and is concentrated into the vacuolar compartment. A chimeric gene construct in which an inducible promoter, insensitive to nitrogen repression, drives the expression of UapC?GFP, allowed us to demonstrate that the ammoniumdependent redistribution of UapC can be dissociated from the transcriptional repression of the gene. These results provide further support for the occurrence of endocytosis and the lysosomal?endosomal function of the vacuolar compartment in A. nidulans.