Ferrichrome induces endosome to plasma membrane cycling of the ferrichrome transporter, Arn1p, in Saccharomyces cerevisiae.
Siderophores are small iron-binding molecules that are synthesized and secreted in the iron-free form by microorganisms. Saccharomyces cerevisiae takes up iron bound to siderophores by two separate systems, one of which requires the ARN family of sidero phore-iron transporters. Arn1p and Arn3p are expressed in endosome-like intracellular vesicles. Here we present evidence that, in the absence of its specific substrate, ferrichrome, Arn1p is sorted directly from the Golgi to the endosomal compartment and does not cycle to the plasma membrane. When cells are exposed to ferrichrome at low concentrations, Arn1p stably relocalizes to the plasma membrane. At higher concentrations of ferrichrome, Arn1p relocalizes to the plasma membrane and rapidly undergoes endocytosis. Plasma membrane localization of Arn1p occurs only in the presence of its specific substrate, and not in the presence of other siderophores. Despite expression of Arn1p on the plasma membrane, mutant strains with defects in endocytosis exhibit reduced uptake of ferrichrome-iron. Thus, siderophores influence the trafficking of the Arn transporters within the cell and this trafficking is important for transporter function.
Liver Diseases Section, NIDDK, National Institutes of Health, Building 10, Room 9B16, 10 Center Drive, Bethesda, MD 20892-1800, USA.
Youngwoo
Y
Kim
Cheol-Won
CW
Yun
Caroline C
CC
Philpott
D002462:Cell Membrane / Q000378:metabolism*; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism*; D005291:Ferrichrome / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism*; D017262:Siderophores / Q000378:metabolism; D013379:Substrate Specificity
C410163:Arn1 protein, S cerevisiae; D026901:Membrane Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; D017262:Siderophores; D005291:Ferrichrome