Drug abuse is a major social problem in the United States, with an estimated 15 million individuals addicted and millions more incarcerated, in addition to many billions of dollars of direct and indirect costs. Abused drugs share two common properties: they provide an initial rewarding """"""""high,"""""""" and their use sets in motion a chain of neurochemical changes that ultimately lead to continued drug-seeking behavior, often despite diminished satisfaction by the user. Many abused drugs affect the neuromodulator dopamine, which acts through binding and activation of a family of five G protein-coupled receptors. Dopamine receptors are targets for regulation by G protein-coupled receptor kinases (GRKs), which phosphorylate dopamine-bound, activated receptors and reduce the ability of these receptors to activate downstream signaling pathways. We have created mice bearing targeted deletion of the GRK6 gene, and here show that these knockout animals exhibit a profound supersensitivity to the locomotor effects of cocaine. Cocaine acts by inhibiting the presynaptic transporters, which remove released dopamine from synapses, allowing endogenous dopamine to accumulate to high levels and to activate dopamine receptors to a high degree. These GRK6 knockout animals appear to have normal levels of dopamine receptors, but exhibit a markedly increased coupling of these receptors to G proteins. These results suggest the hypothesis that dopamine receptor regulation by GRK6 is an important component of the mechanisms that control dopamine receptor responsiveness to drugs of abuse and that altered GRK6 function may be a predisposing factor favoring drug addiction. We will use studies in genetically-modified mice and in model cells systems to define the importance of GRK6 regulation of dopamine receptors for drug abuse. We will determine whether loss of GRK6 affects responses to other drugs of abuse, and investigate the role of GRK6 in additional behavioral and neurochemical correlates of drug addiction. We will identify the dopamine receptor subtype(s) that GRK6 acts on in mouse striatum, and investigate whether other GRKs have similar effects. Finally, we will use transgenic and conditional knockout approaches in mice to explore whether dopamine receptor regulation by GRK6 is important postsynaptically, presynaptically, or both. The results of these studies will define the role of GRK6 in setting the basal tone of dopamine signaling in the striatum. ? ? ?

Agency
National Institute of Health (NIH)
Institute
National Institute on Drug Abuse (NIDA)
Type
Research Project (R01)
Project #
5R01DA016347-04
Application #
7217257
Study Section
Molecular Neuropharmacology and Signaling Study Section (MNPS)
Program Officer
Lin, Geraline
Project Start
2004-08-15
Project End
2009-03-31
Budget Start
2007-04-01
Budget End
2008-03-31
Support Year
4
Fiscal Year
2007
Total Cost
$285,307
Indirect Cost
Name
Duke University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
044387793
City
Durham
State
NC
Country
United States
Zip Code
27705
Managò, Francesca; Espinoza, Stefano; Salahpour, Ali et al. (2012) The role of GRK6 in animal models of Parkinson's disease and L-DOPA treatment. Sci Rep 2:301
Schmalzigaug, Robert; Rodriguiz, Ramona M; Bonner, Pamela E et al. (2009) Impaired fear response in mice lacking GIT1. Neurosci Lett 458:79-83
Cai, Xinjiang; Wu, Jiao-Hui; Exum, Sabrina T et al. (2009) Reciprocal regulation of the platelet-derived growth factor receptor-beta and G protein-coupled receptor kinase 5 by cross-phosphorylation: effects on catalysis. Mol Pharmacol 75:626-36
Raehal, Kirsten M; Schmid, Cullen L; Medvedev, Ivan O et al. (2009) Morphine-induced physiological and behavioral responses in mice lacking G protein-coupled receptor kinase 6. Drug Alcohol Depend 104:187-96
Schmalzigaug, Robert; Rodriguiz, Ramona M; Phillips, Lindsey E et al. (2009) Anxiety-like behaviors in mice lacking GIT2. Neurosci Lett 451:156-61
Kahn, Richard A; Bruford, Elspeth; Inoue, Hiroki et al. (2008) Consensus nomenclature for the human ArfGAP domain-containing proteins. J Cell Biol 182:1039-44
Schmalzigaug, Robert; Phee, Hyewon; Davidson, Collin E et al. (2007) Differential expression of the ARF GAP genes GIT1 and GIT2 in mouse tissues. J Histochem Cytochem 55:1039-48
Premont, Richard T; Gainetdinov, Raul R (2007) Physiological roles of G protein-coupled receptor kinases and arrestins. Annu Rev Physiol 69:511-34
Wu, Jiao-Hui; Goswami, Robi; Cai, Xinjiang et al. (2006) Regulation of the platelet-derived growth factor receptor-beta by G protein-coupled receptor kinase-5 in vascular smooth muscle cells involves the phosphatase Shp2. J Biol Chem 281:37758-72
Liu, Songling; Premont, Richard T; Kontos, Christopher D et al. (2005) A crucial role for GRK2 in regulation of endothelial cell nitric oxide synthase function in portal hypertension. Nat Med 11:952-8