Studies of the role of a particulate folate-binding protein in the uptake of 5-methyltetrahydrofolate by cultured human KB cells.
J Biol Chem
; 260(28): 14911-7, 1985 Dec 05.
Article
em En
| MEDLINE
| ID: mdl-4066659
ABSTRACT
The characteristics of the uptake by human epidermoid carcinoma (KB) cells of 5-methyltetrahydrofolate at extracellular concentrations in the physiologic range and the possible role of a membrane-associated folate binder in folate uptake by KB cells have been investigated. Uptake of 5-methyltetrahydrofolate was specific, saturable, and time-, temperature-, and concentration-dependent. Trypsin treatment released 50% of the 5-methyltetrahydrofolate accumulated by KB cells at 4 degrees C, but only 12% at 37 degrees C, indicating that most of the accumulated ligand was intracellular at 37 degrees C, thus demonstrating transport. Accumulated 5-methyltetrahydrofolate was bound to a membrane-associated protein which required detergent for its solubilization, and a significant amount of which was oriented to the cell exterior as demonstrated by its release by trypsin treatment of intact KB cells. The membrane-associated folate binder was immunoprecipitated by antiserum to purified human placental folate receptor, and this antiserum inhibited 5-methyltetrahydrofolate uptake by intact KB cells in a concentration-dependent manner. These data support the hypothesis that the membrane-associated folate-binding protein of human cells participates in the transport of folates under physiologic conditions.
Buscar no Google
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Carcinoma de Células Escamosas
/
Proteínas de Transporte
/
Tetra-Hidrofolatos
/
Receptores de Superfície Celular
Limite:
Humans
Idioma:
En
Revista:
J Biol Chem
Ano de publicação:
1985
Tipo de documento:
Article