Cholesterol as a modulator of cannabinoid receptor CB2 signaling

Abstract

Signaling through integral membrane G protein-coupled receptors (GPCRs) is influenced by lipid composition of cell membranes. By using novel high affinity ligands of human cannabinoid receptor CB2, we demonstrate that cholesterol increases basal activation levels of the receptor and alters the pharmacological categorization of these ligands. Our results revealed that (2-(6-chloro-2-((2,2,3,3-tetramethylcyclopropane-1-carbonyl)imino)benzo[d]thiazol-3(2H)-yl)ethyl acetate ligand (MRI-2646) acts as a partial agonist of CB2 in membranes devoid of cholesterol and as a neutral antagonist or a partial inverse agonist in cholesterol-containing membranes. The differential effects of a specific ligand on activation of CB2 in different types of membranes may have implications for screening of drug candidates in a search of modulators of GPCR activity. MD simulation suggests that cholesterol exerts an allosteric effect on the intracellular regions of the receptor that interact with the G-protein complex thereby altering the recruitment of G protein.

Comparative Study of State-Dependent Cholesterol Binding Sites in Adenosine A2A and A1 Receptors Using Coarse-Grained Molecular Dynamics Simulations in Biologically Relevant Membranes

“…For example, cholesterol was recently shown to act as a positive allosteric modulator of the cannabinoid receptor CB2, since depletion of cholesterol from the plasma membrane decreases its activity, both in the presence of agonists and in the apo state. 118 Furthermore, cholesterol experimentally is a known stabilizer of β 2 adrenergic receptor (β 2 AR) 39 and A 2A R 82 and has been suggested as allosteric modulator of cholecystokinin 1 (CCK1) receptor, 119,47 cannabinoid CB2 receptor, 120 μ-opioid Mu 1 receptor (OPRM1), 121 oxytocin receptor (OXTR). 122 Also, it has been observed that the signaling of A 2A R, coupled to Gα s is reduced with cholesterol depletion; 82 this indicates that cholesterol plays an important role in G αs mediated cAMP accumulation, independently of ligand binding stimulation.…”

Insights into the Role of Membrane Lipids in the Structure, Function and Regulation of Integral Membrane Proteins

“…Cholesterol Activity regulation [8,9] Activity and changes in conformation [10], Modulation of substrate binding affinity [11] Channel inhibition [12] Activation [13], Signalling [14,15], Stability [16,17], Allosteric regulation [18], Lower affinity ligand binding [17], Oligomerisation [19][20][21][22][23] PA Activity [24] Stabilisation [25] PE Dimer formation and function [26], Dimer formation [27], conformer stability [28] Conformer stabilisation and channel desensitisation [29] Agonist and antagonist binding affinities [30], Increase G protein coupling [31,32] Protein assembly [33] PC Dimerisation [34], β-arrestin interaction and function [35], Increase G protein coupling [31] PG Oligomerisation and function [36] Conformer stabilisation and channel desensitisation [37] Increase G protein coupling [30,38], Active conformer stability [39], β-arrestin interaction and function [35], Decrease G protein coupling [31] PS Dimer formation [27], Stabilisation [25], Dimerisation [34], Decrease G protein coupling [31] PI Dimer formation and function…”

“…It has long been known that cholesterol has a key role in GPCR structure and function [94]. Cholesterol directly affects the ligand-binding ability of several GPCRs, including the subtype 2 galanin receptor and the serotonin 1A receptor [95], and there is evidence that cholesterol also plays a role in GPCR signalling, for example, increasing basal activity of the cannabinoid 2 receptor [14]. In the recent study of the class F GPCR, Smoothened, cholesterol is revealed to traffic through a channel in the receptor and play a fundamental role in receptor activation [13].…”

Nanoscale Sub-Compartmentalization of the Dendritic Spine Compartment

“…CBRs are also influenced by the lipid composition of the cell membrane [ 171 ]. In particular, cholesterol has been reported to negatively modulate the activity of CBR1 in nerve cells [ 172 ] and a specific cholesterol binding site has been described in the CBR1 molecule [ 145 ].…”

“…In particular, cholesterol has been reported to negatively modulate the activity of CBR1 in nerve cells [ 172 ] and a specific cholesterol binding site has been described in the CBR1 molecule [ 145 ]. Likewise, cholesterol has recently been reported to increase the basal activation levels of the CBR2 receptor by exerting an allosteric effect on the intracellular regions of the receptor [ 171 ]. Considering the retrograde regulatory effects of CBRs on neurotransmitter release [ 44 ] lipid compartmentalization by membrane cholesterol is of considerable importance as it provides additional regulatory check points of neurotransmitter receptor function.…”