Role of receptor internalization in the agonist‐induced desensitization of cannabinoid type 1 receptors

Abstract

Agonist‐induced internalization of G protein‐coupled receptors (GPCRs) is an important mechanism for regulating signaling transduction of functional receptors at the plasma membrane. We demonstrate here that both caveolae/lipid‐rafts‐ and clathrin‐coated‐pits‐mediated pathways were involved in agonist‐induced endocytosis of the cannabinoid type 1 receptor (CB1R) in stably transfected human embryonic kidney (HEK) 293 cells and that the internalized receptors were predominantly sorted into recycling pathway for reactivation. The treatment of CB1 receptors with the low endocytotic agonist Δ9‐THC induced a faster receptor desensitization and slower resensitization than the high endocytotic agonist WIN 55,212‐2. In addition, the blockade of receptor endocytosis or recycling pathway markedly enhanced agonist‐induced CB1 receptor desensitization. Furthermore, co‐expression of phospholipase D2, an enhancer of receptor endocytosis, reduced CB1 receptor desensitization, whereas co‐expression of a phospholipase D2 negative mutant significantly increased the desensitization after WIN 55,212‐2 treatment. These findings provide evidences for the importance of receptor endocytosis in counteracting CB1 receptor desensitization by facilitating receptor reactivation. Moreover, in primary cultured neurons, the low endocytotic agonist Δ9‐THC or anandamide exhibited a greater desensitization of endogenous CB1 receptors than the high endocytotic agonist WIN 55,212‐2, CP 55940 or 2‐arachidonoyl glycerol, indicating that cannabinoids with high endocytotic efficacy might cause reduced development of cannabinoid tolerance to some kind cannabinoid‐mediated effects.

Cannabinoid receptor 1 mediates high glucose-induced apoptosis via endoplasmic reticulum stress in primary cultured rat mesangial cells

“…In accordance with these reports and our expectation, our study revealed that HG stimulated the levels of CB 1 R proteins in rat mesangial cells. Similar to other G proteincoupled receptors, CB 1 R is internalized following protracted agonist exposure (50), and internalized receptors are predominantly sorted into the recycling pathway for reactivation (62). To determine whether HG activates CB 1 R and upregulates its expression, we expressed C-terminal GFP-tagged CB 1 R in HEK293 cells, because the transfection efficiency in rat mesangial cells was too low to show the internalization.…”

Differential β-arrestin2 requirements for constitutive and agonist-induced internalization of the CB1 cannabinoid receptor

“…This has been demonstrated in many cell lines, including CHO (Rinaldi-Carmona et al, 1998), AtT20 Jin et al, 1999;Roche et al, 1999), F11 (Coutts et al, 2001), neuroblastoma N18TG2 (Keren and Sarne, 2003) and HEK293 (Keren and Sarne, 2003;Leterrier et al, 2004) cells, as well as in hippocampal neurons, which naturally express CB 1 R (Coutts et al, 2001;Leterrier et al, 2006). According to different studies, this agonist-induced CB 1 R endocytosis occurs via clathrin-and/or caveolin-mediated pathways in different cell types (Bari et al, 2008;Hsieh et al, 1999;Keren and Sarne, 2003;Wu et al, 2008).…”

SNO-ing at the Nociceptive Synapse?

“…Potent SNO-mediated inhibition was also observed for lysophosphatidic acid receptors, whereas S-nitrosylation facilitated signaling of muscarinic receptors (Kokkola et al, 2005). By S-nitrosylation of ␤-arrestin, nitric oxide may modify opioid (Bohn et al, 1999(Bohn et al, , 2000(Bohn et al, , 2002Gainetdinov et al, 2004) and cannabinoid (Rubino et al, 2006;Wu et al, 2008) tolerance and dependence. Although not directly demonstrated in the context of S-nitrosylation, it is well accepted that inhibition of neuronal NOS reduces morphine tolerance (Kolesnikov et al, 1993;Elliott et al, 1994), which reflects the dynamics of endocytotic cycling of the receptor between membrane and clathrin coated pits.…”