Clustered folate receptors deliver 5-methyltetrahydrofolate to cytoplasm of MA104 cells

Eric J. Smart, Chieko Mineo, Richard G W Anderson

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79 Scopus citations


Previously, a high affinity, glycosylphosphatidylinositol-anchored receptor for folate and a caveolae internalization cycle have been found necessary for potocytosis of 5-methyltetrahydrofolate in MA104. We now show by cell fractionation that folate receptors also must be clustered in caveolae for potocytosis. An enriched fraction of caveolae from control cells retained 65-70% of the [3H]folic acid bound to cells in culture. Exposure of cells to the cholesterol-binding drug, filipin, which is known to uncluster receptors, shifted ~50% of the bound [3H]folic acid from the caveolac fraction to the noncaveolac membrane fraction and markedly inhibited internalization of [3H]folic acid. An mAb directed against the folate receptor also shifted ~50% of the caveolae-associated [3H]folic acid to noncaveolac membrane, indicating the antibody perturbs the normal receptor distribution. Concordantly, the mAb inhibited the delivery of 5- methyl[3H]tetrahydrofolate to the cytoplasm. Receptor bound 5- methyl[3H]tetrahydrofolate moved directly from caveolae to the cytoplasm and was not blocked by phenylarsine oxide, an inhibitor of receptor-mediated endocytosis. These results suggest cell fractionation can be used to study the uptake of molecules by caveolae.

Original languageEnglish (US)
Pages (from-to)1169-1177
Number of pages9
JournalJournal of Cell Biology
Issue number5
StatePublished - Sep 1996

ASJC Scopus subject areas

  • Cell Biology


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