Gαi/o-coupled receptor-mediated sensitization of adenylyl cyclase: 40 years later

doi:10.1016/j.ejphar.2015.05.014

European Journal of Pharmacology

Volume 763, Part B, 15 September 2015, Pages 223-232

https://doi.org/10.1016/j.ejphar.2015.05.014 Get rights and content

Abstract

Heterologous sensitization of adenylyl cyclase (also referred to as superactivation, sensitization, or supersensitization of adenylyl cyclase) is a cellular adaptive response first described 40 years ago in the laboratory of Dr. Marshall Nirenberg. This apparently paradoxical cellular response occurs following persistent activation of Gα_i/o-coupled receptors and causes marked enhancement in the activity of adenylyl cyclases, thereby increasing cAMP production. Since our last review in 2005, significant progress in the field has led to a better understanding of the relevance of, and the cellular biochemical processes that occur during the development and expression of heterologous sensitization. In this review we will discuss the recent advancements in the field and the mechanistic hypotheses on heterologous sensitization.

Section snippets

Introduction to heterologous sensitization

The history of and basic concepts involving heterologous sensitization of adenylyl cyclase were extensively discussed in our previous review (Watts and Neve, 2005). Thus, the present review will provide a limited introduction describing the history of this topic, and then incorporate recent findings into our current understanding of this paradoxical phenomenon, first described forty years ago in the laboratory of Dr. Marshall Nirenberg (Sharma et al., 1975).

G protein-coupled receptors (GPCRs)

Gα_i/o subunits

Heterologous sensitization is a phenomenon shared by numerous Gα_i/o-coupled receptors and, because of this, is linked to activation of Gα_i/o proteins. Mechanistically, inactivation of Gα_i/o with pertussis toxin treatment blunts receptor-mediated heterologous sensitization (Watts, 2002). Pretreatment with pertussis toxin leads to ADP-ribosylation of Gα_i/o subunits, ultimately preventing their activation by receptors. Because pertussis toxin inhibits all isoforms of Gα_i (i.e. Gα_i1, Gα_i2, Gα_i3),

Heterologous sensitization in animals

Demonstration in animal models was an important step in the establishment of heterologous sensitization as a more physiologically relevant receptor response following prolonged activation of Gα_i/o-coupled receptors. For example, in 1988 Nestler and Tallman observed that following a five-day chronic treatment of rats with subcutaneous morphine pellets, there was an increase in the amounts of active PKA in the locus coeruleus. These results are consistent with the known outcomes of heterologous

Conclusions and future perspectives

Heterologous sensitization is characterized by a seemingly paradoxical increase in the activity of adenylyl cyclases following prolonged activation of Gα_i/o-coupled receptors. Increasing evidence suggests that several proteins are involved in the development and expression of heterologous sensitization of adenylyl cyclase isoforms. Moreover, there appear to be adenylyl cyclase-isoform specific mechanisms. The reports discussed here suggest that during persistent activation of Gα_i/o-coupled

Disclosures

The authors have no conflicts of interest to disclose. This work was supported by the National Institute of Mental Health [Grants MH060397 and MH101673], the Purdue Research Foundation, and by Purdue University.

Acknowledgments

The authors wish to acknowledge Ms. Isabelle Verona Brust for preparing the figures in the manuscript and Ms. Stacy O. Nall for editorial assistance.

References (133)

M. Abramow-Newerly et al.
RGS proteins have a signalling complex: interactions between RGS proteins and GPCRs, effectors, and auxiliary proteins
Cell Signal.
(2006)
G. Aloisi et al.
Differential induction of adenylyl cyclase supersensitivity by antiparkinson drugs acting as agonists at dopamine D1/D2/D3 receptors vs D2/D3 receptors only: parallel observations from co-transfected human and native cerebral receptors
Neuropharmacology
(2011)
H. Ammer et al.
Morphine dependence in human neuroblastoma SH-SY5Y cells is associated with adaptive changes in both the quantity and functional interaction of PGE1 receptors and stimulatory G proteins
Brain Res.
(1996)
F.A. Antoni et al.
Calcineurin feedback inhibition of agonist-evoked cAMP formation
J. Biol. Chem.
(1995)
T. Avidor-Reiss et al.
Chronic opioid treatment induces adenylyl cyclase V superactivation. Involvement of Gbetagamma
J. Biol. Chem.
(1996)
T. Avidor-Reiss et al.
Opiate-induced adenylyl cyclase superactivation is isozyme-specific
J. Biol. Chem.
(1997)
G.B. Bishop et al.
Abused drugs modulate RGS4 mRNA levels in rat brain: comparison between acute drug treatment and a drug challenge after chronic treatment
Neurobiol. Dis.
(2002)
J.B. Blumer et al.
AGS proteins: receptor-independent activators of G-protein signaling
Trends Pharmacol. Sci.
(2005)
A.D. Boran et al.
Identification of new Gbetagamma interaction sites in adenylyl cyclase 2
Cell Signal.
(2011)
E.A. Boutet-Robinet et al.
Endogenous RGS proteins facilitate dopamine D(2S) receptor coupling to G(alphao) proteins and Ca²⁺ responses in CHO-K1 cells
FEBS Lett.
(2003)

S. Chakrabarti et al.

Biochemical demonstration of mu-opioid receptor association with Gsalpha: enhancement following morphine exposure

Brain Res. Mol. Brain Res.

(2005)

T.K. Chatterjee et al.

A truncated form of RGS3 negatively regulates G protein-coupled receptor stimulation of adenylyl cyclase and phosphoinositide phospholipase C

J. Biol. Chem.

(1997)

M.J. Cismowski et al.

Activation of heterotrimeric G-protein signaling by a ras-related protein. Implications for signal integration

J. Biol. Chem.

(2000)

M.J. Cismowski et al.

Receptor-independent activators of heterotrimeric G-proteins

Life Sci.

(2001)

D. Cooper et al.

Higher-order organization and regulation of adenylyl cyclases

Trends Pharmacol. Sci.

(2006)

S. Diel et al.

Gbetagamma activation site in adenylyl cyclase type II. Adenylyl cyclase type III is inhibited by Gbetagamma

J. Biol. Chem.

(2006)

D.J. Dupre et al.

Signalling complexes associated with adenylyl cyclase II are assembled during their biosynthesis

Cell Signal.

(2007)

R.H. Dworkin et al.

Pharmacologic management of neuropathic pain: evidence-based recommendations

Pain

(2007)

T.E. Graham et al.

Dexras1/AGS-1 inhibits signal transduction from the Gi-coupled formyl peptide receptor to Erk-1/2 MAP kinases

J. Biol. Chem.

(2002)

B.M. Hacker et al.

Cloning, chromosomal mapping, and regulatory properties of the human type 9 adenylyl cyclase (ADCY9)

Genomics

(1998)

M.A. Hanson et al.

Discovery of new GPCR biology: one receptor structure at a time

Structure

(2009)

S.B. Hooks et al.

A role of RGS proteins in drug addiction

Biochem. Pharmacol.

(2008)

G. Iwami et al.

Regulation of adenylyl cyclase by protein kinase A

J. Biol. Chem.

(1995)

S.A. Kotecha et al.

A D2 class dopamine receptor transactivates a receptor tyrosine kinase to inhibit NMDA receptor transmission

Neuron

(2002)

R.J. Lefkowitz

Historical review: a brief history and personal retrospective of seven-transmembrane receptors

Trends Pharmacol. Sci.

(2004)

W.E. McIntire et al.

The G protein beta subunit is a determinant in the coupling of Gs to the beta 1-adrenergic and A2a adenosine receptors

J. Biol. Chem.

(2001)

I.S. Moreira

Structural features of the G-protein/GPCR interactions

Biochim. Biophys. Acta

(2014)

Y. Namkung et al.

G protein-coupled receptor kinase-2 constitutively regulates D2 dopamine receptor expression and signaling independently of receptor phosphorylation

J. Biol. Chem.

(2009)

C.H. Nguyen et al.

Dexras1 blocks receptor-mediated heterologous sensitization of adenylyl cyclase 1

Biochem. Biophys. Res. Commun.

(2005)

R. Nygaard et al.

The dynamic process of beta(2)-adrenergic receptor activati

Cell

(2013)

T.B. Patel et al.

Molecular biological approaches to unravel adenylyl cyclase signaling and function

Gene

(2001)

A.A. Roy et al.

RGS2 interacts with Gs and adenylyl cyclase in living cells

Cell Signal.

(2006)

M. Sato et al.

AGS3 and signal integration by Galpha(s)- and Galpha(i)-coupled receptors: AGS3 blocks the sensitization of adenylyl cyclase following prolonged stimulation of a Galpha(i)-coupled receptor by influencing processing of Galpha(i)

J. Biol. Chem.

(2004)

E. Schallmach et al.

Adenylyl cyclase type II activity is regulated by two different mechanisms: implications for acute and chronic opioid exposure

Neuropharmacology

(2006)

W.F. Schwindinger et al.

Synergistic roles for G-protein gamma3 and gamma7 subtypes in seizure susceptibility as revealed in double knock-out mice

J. Biol. Chem.

(2012)

P.C. Sternweis et al.

Isolation of two proteins with high affinity for guanine nucleotides from membranes of bovine brain

J. Biol. Chem.

(1984)

A. Takesono et al.

Receptor-independent activators of heterotrimeric G-protein signaling pathways

J. Biol. Chem.

(1999)

A. Takesono et al.

Activator of G-protein signaling 1 blocks GIRK channel activation by a G-protein-coupled receptor: apparent disruption of receptor signaling complexes

J. Biol. Chem.

(2002)

R. Taussig et al.

Inhibition of the omega-conotoxin-sensitive calcium current by distinct G proteins

Neuron

(1992)

H. Ammer et al.

Identity of adenylyl cyclase isoform determines the G protein mediating chronic opioid-induced adenylyl cyclase supersensitivity

J. Neurochem.

(2002)

H. Ammer et al.

Chronic activation of inhibitory delta-opioid receptors cross-regulates the stimulatory adenylate cyclase-coupled prostaglandin E1 receptor system in neuroblastoma×glioma (NG108-15) hybrid cells

J. Neurochem.

(1995)

H. Ammer et al.

Adenylyl cyclase supersensitivity in opioid-withdrawn NG108-15 hybrid cells requires Gs but is not mediated by the Gsalpha subunit

J. Pharmacol. Exp. Ther.

(1998)

M. Bastepe et al.

Receptor-mediated adenylyl cyclase activation through XLalpha(s), the extra-large variant of the stimulatory G protein alpha-subunit

Mol. Endocrinol.

(2002)

M.A. Beazely et al.

Protein kinase C and epidermal growth factor stimulation of Raf1 potentiates adenylyl cyclase type 6 activation in intact cells

Mol. Pharmacol.

(2005)

L.M. Bohn et al.

Mu-opioid receptor desensitization by beta-arrestin-2 determines morphine tolerance but not dependence

Nature

(2000)

M.S. Bowers et al.

Nucleus accumbens AGS3 expression drives ethanol seeking through G betagamma

Proc. Natl. Acad. Sci. U. S. A.

(2008)

M.S. Bowers et al.

AGS3: a G-protein regulator of addiction-associated behaviors

Ann. N. Y. Acad. Sci.

(2003)

T.F. Brust et al.

Bias analyses of preclinical and clinical D2 dopamine ligands: studies with immediate and complex signaling pathways

J. Pharmacol. Exp. Ther.

(2015)

S. Chakrabarti et al.

Chronic morphine augments adenylyl cyclase phosphorylation: relevance to altered signaling during tolerance/dependence

Mol. Pharmacol.

(1998)

E. Chalecka-Franaszek et al.

Immunoprecipitation of high-affinity, guanine nucleotide-sensitive, solubilized mu-opioid receptors from rat brain: coimmunoprecipitation of the G proteins G(alpha o), G(alpha i1), and G(alpha i3)

J. Neurochem.

(2000)

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Gαi/o-coupled receptor-mediated sensitization of adenylyl cyclase: 40 years later

Abstract

Section snippets

Introduction to heterologous sensitization

Gαi/o subunits

Heterologous sensitization in animals

Conclusions and future perspectives

Disclosures

Acknowledgments

Cell Signal.

Neuropharmacology

Brain Res.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

Neurobiol. Dis.

Trends Pharmacol. Sci.

Cell Signal.

FEBS Lett.

Brain Res. Mol. Brain Res.

J. Biol. Chem.

J. Biol. Chem.

Life Sci.

Trends Pharmacol. Sci.

J. Biol. Chem.

Cell Signal.

Pain

J. Biol. Chem.

Genomics

Structure

Biochem. Pharmacol.

J. Biol. Chem.

Neuron

Trends Pharmacol. Sci.

J. Biol. Chem.

Biochim. Biophys. Acta

J. Biol. Chem.

Biochem. Biophys. Res. Commun.

Cell

Gene

Cell Signal.

J. Biol. Chem.

Neuropharmacology

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

J. Biol. Chem.

Neuron

Identity of adenylyl cyclase isoform determines the G protein mediating chronic opioid-induced adenylyl cyclase supersensitivity

J. Neurochem.

Chronic activation of inhibitory delta-opioid receptors cross-regulates the stimulatory adenylate cyclase-coupled prostaglandin E1 receptor system in neuroblastoma×glioma (NG108-15) hybrid cells

J. Neurochem.

Adenylyl cyclase supersensitivity in opioid-withdrawn NG108-15 hybrid cells requires Gs but is not mediated by the Gsalpha subunit

J. Pharmacol. Exp. Ther.

Receptor-mediated adenylyl cyclase activation through XLalpha(s), the extra-large variant of the stimulatory G protein alpha-subunit

Mol. Endocrinol.

Protein kinase C and epidermal growth factor stimulation of Raf1 potentiates adenylyl cyclase type 6 activation in intact cells

Mol. Pharmacol.

Mu-opioid receptor desensitization by beta-arrestin-2 determines morphine tolerance but not dependence

Nature

Nucleus accumbens AGS3 expression drives ethanol seeking through G betagamma

Proc. Natl. Acad. Sci. U. S. A.

AGS3: a G-protein regulator of addiction-associated behaviors

Ann. N. Y. Acad. Sci.

Bias analyses of preclinical and clinical D2 dopamine ligands: studies with immediate and complex signaling pathways

J. Pharmacol. Exp. Ther.

Chronic morphine augments adenylyl cyclase phosphorylation: relevance to altered signaling during tolerance/dependence

Mol. Pharmacol.

Immunoprecipitation of high-affinity, guanine nucleotide-sensitive, solubilized mu-opioid receptors from rat brain: coimmunoprecipitation of the G proteins G(alpha o), G(alpha i1), and G(alpha i3)

J. Neurochem.

Gα_i/o-coupled receptor-mediated sensitization of adenylyl cyclase: 40 years later

Gα_i/o subunits