The precise mechanism by which the cellular uptake of the endocannabinoid anandamide (AEA) occurs has been the source of much debate. In the current study, we show that neuronal differentiated CAD (dCAD) cells accumulate anandamide by a process that is inhibited in a dose-dependent manner by N-(4-hydroxyphenyl)arachidonylamide (AM404). We also show that dCAD cells express functional fatty acid amide hydrolase, the enzyme primarily responsible for anandamide metabolism. Previous data from our laboratory indicated that anandamide uptake occurs by a caveolae-related endocytic mechanism in RBL-2H3 cells. In the current study, we show that anandamide uptake by dCAD cells may also occur by an endocytic process that is associated with detergent-resistant membrane microdomains or lipid rafts. Nystatin and progesterone pretreatment of dCAD cells significantly inhibited anandamide accumulation. Furthermore, RNA interference (RNAi)-mediated knockdown of dynamin 2, a protein involved in endocytosis, blocked the internalization of the fluorescently labeled anandamide analog SKM 4-45-1 ([3Ј,6Ј-bis(acetyloxy)-. RNAi-mediated knockdown of the ␤2 subunit of the clathrin-associated activator protein 2 complex had no effect on SKM 4-45-1 internalization. We were surprised to find that dynamin 2 knockdown in dCAD cells did not affect [ 3 H]AEA uptake. However, dynamin 2 knockdown caused a significant increase in the overall levels of intact [3 H]AEA associated with the cells, suggesting that trafficking of [ 3 H]AEA to FAAH had been disrupted. This finding may be the result of an accumulation of the anandamide carrier protein in detergent-resistant membranes after dynamin 2 knockdown. Our studies provide evidence that the cellular uptake of anandamide may occur by a dynamin 2-dependent, caveolae-related endocytic process in dCAD cells.The endocannabinoid anandamide (AEA) is an agonist of the cannabinoid 1 and 2 receptors (Matsuda et al., 1990;Munro et al., 1993) and some vanilloid type ion channels (Di Marzo et al., 2001;Voets and Nilius, 2003). AEA is internalized by most cell types and is thought to be metabolized primarily by the intracellular enzyme fatty acid amide hydrolase (FAAH) (Deutsch and Chin, 1993;Di Marzo et al., 1994;Cravatt et al., 1996). Previous studies from our laboratory have indicated that AEA uptake potentially occurs by a caveolae-related, or clathrin-independent, endocytic process (McFarland et al., 2004). Interestingly, neurons are not thought to express caveolin-1 but do exhibit lipid raft-related endocytic processes (Cameron et al., 1997). Thus, our studies seek to validate a neuronal-like cell line as a useful model in the study of AEA uptake and to show that AEA uptake can be disrupted by using molecular inhibitors that are specifically targeted to endocytic processes.Cath.a cells display neuronal properties and express panneuronal markers but lack classic neuronal morphology (Suri et al., 1993;Lazaroff, 1996). Cath.a differentiated (CAD) cells are derived from the Cath.a cell line and are chara...

The cannabinoid field is currently an active research area.

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The cannabinoid field is currently an active research area due to a proposed role for endogenous cannabinoids, such as anandamide (AEA), in various physiological processes. AEA is synthesized on‐demand and released into the extracellular space, where it acts as an agonist at both the central and peripheral nervous system cannabinoid receptors CB1 and CB2, respectively. To cease signaling, AEA is transported into cells, where it is metabolized by the enzyme fatty acid amide hydrolase (FAAH1). However, very little is known regarding AEA transport. Our lab has previously identified caveolae‐dependent endocytosis as a mechanism for AEA transport. We recently showed that the protein ERp57 localizes to caveolae during AEA transport. Interestingly, the transcription factor STAT3, which interacts with ERp57 and has been implicated in the regulation of FAAH1 gene expression, localizes to caveolae in its inactive form. We propose that in response to AEA transport, ERp57 and STAT3 work together to up‐regulate FAAH1 gene transcription. Such increases in FAAH1 expression levels have previously been associated with increased AEA transport. We are using RNAi technology to explore the role of ERp57 in STAT3‐regulated FAAH1 transcription. Additionally, we are using various techniques to identify changes in both FAAH1 expression and STAT3 activation in response to AEA uptake. Research funded by NIH Grant R21DA018844.