Abstract:
Intracellular signaling systems of G protein-coupled receptors are well
established, but their role in paracrine regulation of adjacent cells is
generally considered as a tissue-specific mechanism. We have shown previously
that AT(1) receptor (AT(1)R) stimulation leads to diacylglycerol lipase-mediated
transactivation of co-expressed CB(1)Rs in Chinese hamster ovary cells. In the
present study we detected a paracrine effect of the endocannabinoid release from
Chinese hamster ovary, COS7, and HEK293 cells during the stimulation of AT(1)
angiotensin receptors by determining CB(1) cannabinoid receptor activity with
bioluminescence resonance energy transfer-based sensors of G protein activation
expressed in separate cells. The angiotensin II-induced, paracrine activation of
CB(1) receptors was visualized by detecting translocation of green fluorescent
protein-tagged beta-arrestin2. Mass spectrometry analyses have demonstrated
angiotensin II-induced stimulation of 2-arachidonoylglycerol production, whereas
no increase of anandamide levels was observed. Stimulation of G(q/11)-coupled
M(1), M(3), M(5) muscarinic, V(1) vasopressin, alpha(1a) adrenergic, B(2)
bradykinin receptors, but not G(i/o)-coupled M(2) and M(4) muscarinic receptors,
also led to paracrine transactivation of CB(1) receptors. These data suggest
that, in addition to their retrograde neurotransmitter role, endocannabinoids
have much broader paracrine mediator functions during activation of
G(q/11)-coupled receptors.
