Journal
JOURNAL OF BIOLOGICAL CHEMISTRY
Volume 279, Issue 40, Pages 41991-41997Publisher
AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
DOI: 10.1074/jbc.M407250200
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- NIDA NIH HHS [R21 DA13268] Funding Source: Medline
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The mechanisms responsible for the uptake and cellular processing of the endogenous cannabinoid anandamide are not well understood. We propose that anandamide uptake may occur via a caveola/lipid raft-related endocytic process in RBL-2H3 cells. Inhibitors of caveola-related (clathrin-independent) endocytosis reduced anandamide transport by similar to 50% compared with the control. Fluorescein derived from fluorescently labeled anandamide colocalized with protein markers of caveolae at early time points following transport. In this study, we have also identified a yet unrecognized process involved in trafficking events affecting anandamide following its uptake. Following uptake of [H-3] anandamide by RBL-2H3 cells, we found an accumulation of tritium in the caveolin-rich membranes. Inhibitors of both anandamide uptake and metabolism blocked the observed enrichment of tritium in the caveolin-rich membranes. Mass spectrometry of subcellular membrane fractions revealed that the tritium accumulation observed in the caveolin-rich membrane fraction was not representative of intact anandamide, suggesting that following metabolism by the enzyme fatty acid amide hydrolase ( FAAH), anandamide metabolites are rapidly enriched in caveolae. Furthermore, HeLa cells, which do not express high levels of FAAH, showed an accumulation of tritium in the caveolin-rich membrane fraction only when transfected with FAAH cDNA. Western blot and immunocytochemistry analyses of RBL-2H3 cells revealed that FAAH was localized in intracellular compartments distinct from caveolin-1 localization. Together, these data suggest that following uptake via caveola/lipid raft-related endocytosis, anandamide is rapidly metabolized by FAAH, with the metabolites efficiently recycled to caveolin-rich membrane domains.
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