Cannabinoid Receptor Activation Differentially Regulates the Various Adenylyl Cyclase Isozymes

Abstract

Two cannabinoid receptors belonging to the superfamily of G protein-coupled membrane receptors have been identified and cloned: the neuronal cannabinoid receptor (CB1) and the peripheral cannabinoid receptor (CB2). They have been shown to couple directly to the G 10 subclass of G proteins and to mediate inhibition of adenylyl cyclase upon binding of a cannabinoid agonist. In several cases, however, cannabinoids have been reported to stimulate adenylyl cyclase activity, although the mechanism by which they did so was unclear. With the cloning of nine adenylyl cyclase isozymes with various properties, including different sensitivities to a~,a10, and y subunits, it became important to assess the signaling pattern mediated by each cannabinoid receptor via the different adenylyl cyclase isozymes. In this work, we present the results of cotransfection experiments between the two types of cannabinoid receptors and the nine adenylyl cyclase isoforms. We found that independently of the method used to stimulate specific adenylyl cyclase isozymes (e.g., ionomycin, forskolin, constitutively active a5, thyroid-stimulating hormone receptor activation), activation of the cannabinoid receptors CB1 and CB2 inhibited the activity of adenylyl cyclase types I, V, VI, and VIII, whereas types II, IV, and VII were stimulated by cannabinoid receptor activation. The inhibition of adenylyl cyclase type Ill by cannabinoids was observed only when forskolin was used as stimulant. The activity of adenylyl cyclase type IX was inhibited only marginally by cannabinoids. KeyWords: Cannabinoid receptor-Forskolin-Adenylyl cyclase-GTP-binding proteins-Cyclic AMP.

A Predominant Role for Inhibition of the Adenylate Cyclase/Protein Kinase A Pathway in ERK Activation by Cannabinoid Receptor 1 in N1E-115 Neuroblastoma Cells

“…Cannabinoids are less potent inhibitors of adenylate cyclase isoforms expressed by C6 glioma cells than those expressed by NG108 -15 neuroblastoma cells or N18TG2 neuroblastoma cells (8,14), suggesting that inhibition of AC by the CB1 receptor may not be the predominant pathway for ERK activation in cells of glial origin. Galve-Roperh et al (24) also used the synthetic agonist HU-210, which may activate different G-protein coupled pathways than those activated by WIN (44).…”

“…Regulation of AC can occur through both ␣ and ␤␥ subunits depending on the isoforms of AC expressed by the cells (12,13). Cannabinoids increase cAMP production in CHO cells expressing AC II, IV, or VII through ␤␥ subunits but decrease activity in cells expressing AC I, V, VI, and VIII (14). In addition, cannabinoids have been linked to sphingomyelin hydrolysis and ceramide generation in glial and glioma cells (15).…”

Differential Roles of CB1 and CB2 Cannabinoid Receptors in Mast Cells

“…We do not yet know whether CB1 is coupled to G i/o or G ␣s in the RBL2H3. Rhee et al (62) report that a key determinant of the outcome of CB1 ligation, in terms of stimulatory or inhibitory effects on cAMP levels, is the representation of AC isoforms in a given cell context. In cells expressing AC isoforms 1, 3, 5, or 8, cannabinoid ligation results in a net suppression of cAMP levels.…”

Functional Role of Tryptophan Residues in the Fourth Transmembrane Domainof the CB2 Cannabinoid Receptor

“…Rabbit AC type V (AC-V) and ␤-galactosidase cDNAs in the pXMD1 vector (Wallach et al, 1994) were described previously (Avidor-Reiss et al, 1997;Rhee et al, 1998). The human CB 2 cDNA in pCDM8 was kindly provided by Dr. S. Munro (Cambridge, U.K.).…”

“…The assay was performed in triplicate as described previously Rhee et al, 1998). In brief, cells cultured in 24-well plates were incubated for 2 h with 0.25 ml/well fresh growth medium containing 5 Ci/ml [2-3 H]adenine.…”