Vs. Subramanian et al., Intracellular trafficking/membrane targeting of human reduced folate carrier expressed in Xenopus oocytes, AM J P-GAST, 281(6), 2001, pp. G1477-G1486
Citations number
46
Categorie Soggetti
da verificare
Journal title
AMERICAN JOURNAL OF PHYSIOLOGY-GASTROINTESTINAL AND LIVER PHYSIOLOGY
The major cellular pathway for uptake of the vitamin folic acid, including
its absorption in the intestine, is via a plasma membrane carrier system, t
he reduced folate carrier (RFC). Very little is known about the mechanisms
that control intracellular trafficking and plasma membrane targeting of RFC
. To begin addressing these issues, we used Xenopus oocyte as a model syste
m and examined whether the signal that targets the protein to the plasma me
mbrane is located in the COOH-terminal cytoplasmic tail or in the backbone
of the polypeptide. We also examined the role of microtubules and microfila
ments in intracellular trafficking of the protein. Confocal imaging of huma
n RFC (hRFC) fused to the enhanced green fluorescent protein (hRFC-EGFP) sh
owed that the protein was expressed at the plasma membrane, with expression
confined almost entirely to the animal pole of the oocyte. Localization of
hRFC at the plasma membrane was not affected by partial or total truncatio
n of the COOH-terminal tail of the polypeptide, whereas a construct of the
cytoplasmic tail fused to EGFP was not found at the plasma membrane. Disrup
tion of microtubules, but not microfilaments, prevented hRFC expression at
the plasma membrane. These results demonstrate that the molecular determina
nt(s) that directs plasma membrane targeting of hRFC is located within the
backbone of the polypeptide and that intact microtubules, but not microfila
ments, are essential for intracellular trafficking of the protein.