Biomaterial Database

Distinguishing between folate receptor-alpha-mediated transport and reduced folate carrier-mediated transport in L1210 leukemia cells. 1995

M J Spinella, and K E Brigle, and E E Sierra, and I D Goldman

Department of Medicine, Virginia Commonwealth University, Medical College of Virginia, Richmond 23298, USA.

L1210 leukemia cells transport reduced folates and methotrexate via a well defined reduced folate carrier system and, in the absence of low folate selective pressure, do not express an alternate endocytotic route mediated by cell surface folate receptors. This laboratory previously described an L1210 leukemia cell line, MTXrA, with acquired resistance to methotrexate (MTX) due to the loss of mobility of the reduced folate carrier. We now report on the transfection of MTXrA with a cDNA encoding the murine homolog of the human folate receptor isoform of KB cells to produce MTXrA-TF1, which constitutively expresses high levels of FR-alpha. MTXrA-TF1 and L1210 cells were utilized to compare transport of methotrexate mediated by FR-alpha and the reduced folate carrier, respectively. Methotrexate influx in the two lines was similar when the extracellular level was 0.1 microM, but as the methotrexate concentration increased, influx via the reduced folate carrier increased in comparison to influx mediated by FR-alpha. Transport kinetics indicated both a approximately 20-fold lower influx Kb and Vmax for MTXrA-TF1 as compared to L1210 cells. The two cell lines exhibited distinct influx properties. Methotrexate influx in MTXrA-TF1 was markedly inhibited by 50 nM folic acid and metabolic poisons. In L1210 cells, 1.0 microM folic acid did not affect MTX influx, and metabolic poisons either had no effect on or increased methotrexate influx. Removal of extracellular chloride markedly inhibited transport in MTXrA-TF1 but stimulated influx in L1210 cells. When the pH was decreased to 6.2, methotrexate influx was not altered in MTXrA-TF1 but was reduced in L1210 cells. Probenecid and sulfobromophthalein inhibit methotrexate influx in both L1210 and MTXrA-TF1 cell lines; however, inhibition in MTXrA-TF1 could be accounted for on the basis of inhibition of methotrexate binding to FR-alpha. The data indicate that the reduced folate carrier and FR-alpha function independently and exhibit distinct properties. FR-alpha expressed at sufficient levels can mediate influx of MTX and folates into cells at rates comparable to the reduced folate carrier and hence has pharmacologic and physiologic importance.

UI	MeSH Term	Description	Entries
D007477	Ions	An atom or group of atoms that have a positive or negative electric charge due to a gain (negative charge) or loss (positive charge) of one or more electrons. Atoms with a positive charge are known as CATIONS; those with a negative charge are ANIONS.
D007939	Leukemia L1210	An experimental LYMPHOCYTIC LEUKEMIA of mice.	Leukemia L 1210,L 1210, Leukemia,L1210, Leukemia
D008565	Membrane Proteins	Proteins which are found in membranes including cellular and intracellular membranes. They consist of two types, peripheral and integral proteins. They include most membrane-associated enzymes, antigenic proteins, transport proteins, and drug, hormone, and lectin receptors.	Cell Membrane Protein,Cell Membrane Proteins,Cell Surface Protein,Cell Surface Proteins,Integral Membrane Proteins,Membrane-Associated Protein,Surface Protein,Surface Proteins,Integral Membrane Protein,Membrane Protein,Membrane-Associated Proteins,Membrane Associated Protein,Membrane Associated Proteins,Membrane Protein, Cell,Membrane Protein, Integral,Membrane Proteins, Integral,Protein, Cell Membrane,Protein, Cell Surface,Protein, Integral Membrane,Protein, Membrane,Protein, Membrane-Associated,Protein, Surface,Proteins, Cell Membrane,Proteins, Cell Surface,Proteins, Integral Membrane,Proteins, Membrane,Proteins, Membrane-Associated,Proteins, Surface,Surface Protein, Cell
D008727	Methotrexate	An antineoplastic antimetabolite with immunosuppressant properties. It is an inhibitor of TETRAHYDROFOLATE DEHYDROGENASE and prevents the formation of tetrahydrofolate, necessary for synthesis of thymidylate, an essential component of DNA.	Amethopterin,Methotrexate Hydrate,Methotrexate Sodium,Methotrexate, (D)-Isomer,Methotrexate, (DL)-Isomer,Methotrexate, Dicesium Salt,Methotrexate, Disodium Salt,Methotrexate, Sodium Salt,Mexate,Dicesium Salt Methotrexate,Hydrate, Methotrexate,Sodium, Methotrexate
D011090	Polyenes	Hydrocarbons with more than one double bond. They are a reduced form of POLYYNES.	Cumulenes
D011339	Probenecid	The prototypical uricosuric agent. It inhibits the renal excretion of organic anions and reduces tubular reabsorption of urate. Probenecid has also been used to treat patients with renal impairment, and, because it reduces the renal tubular excretion of other drugs, has been used as an adjunct to antibacterial therapy.	Benecid,Benemid,Benuryl,Pro-Cid,Probecid,Probenecid Weimer
D011753	Pyrones	Keto-pyrans.
D011956	Receptors, Cell Surface	Cell surface proteins that bind signalling molecules external to the cell with high affinity and convert this extracellular event into one or more intracellular signals that alter the behavior of the target cell (From Alberts, Molecular Biology of the Cell, 2nd ed, pp693-5). Cell surface receptors, unlike enzymes, do not chemically alter their ligands.	Cell Surface Receptor,Cell Surface Receptors,Hormone Receptors, Cell Surface,Receptors, Endogenous Substances,Cell Surface Hormone Receptors,Endogenous Substances Receptors,Receptor, Cell Surface,Surface Receptor, Cell
D002352	Carrier Proteins	Proteins that bind or transport specific substances in the blood, within the cell, or across cell membranes.	Binding Proteins,Carrier Protein,Transport Protein,Transport Proteins,Binding Protein,Protein, Carrier,Proteins, Carrier
D004734	Energy Metabolism	The chemical reactions involved in the production and utilization of various forms of energy in cells.	Bioenergetics,Energy Expenditure,Bioenergetic,Energy Expenditures,Energy Metabolisms,Expenditure, Energy,Expenditures, Energy,Metabolism, Energy,Metabolisms, Energy