Ethanol alters cAMP signal transduction in many cultured cell lines and in cells from actively drinking alcoholics. These changes in cAMP signal transduction have pleiotropic effects on cellular functions since cAMP is an important regulator of many cell processes. The acute and chronic effects of ethanol on cAMP signalling in many cell types are due to an initial inhibition of adenosine uptake by ethanol acting on a specific type of nucleoside transporter. This inhibition leads to an extracellular accumulation of adenosine which then activates adenosine receptors and increases intracellular cAMP levels. After chronic exposure to ethanol, there is an adaptative decrease in receptor-stimulated cAMP production. In addition, after chronic exposure to ethanol, adenosine uptake is no longer inhibited on rechallenge with ethanol. cAMP-dependent protein kinase (PKA) is required for ethanol to inhibit adenosine uptake. Therefore, the loss of ethanol sensitivity of adenosine uptake after chronic exposure to ethanol may be due to decreased cAMP and PKA levels. In this proposal, the role of phosphorylation in reversibly regulating the ethanol sensitivity of nucleoside uptake in the cultured neural cell line, NG108-15, and in human erythrocytes will be determined. The use of NG108-15 cells will allow the determination of whether ethanol- induced changes in extracellular adenosine regulate the ethanol sensitivity of adenosine transport in intact cells. Sealed membranes can be prepared from erythrocytes that exhibit only ethanol-sensitive nucleoside transport. These vesicles can be sequentially phosphorylated or dephosphorylated in vitro allowing the functional consequences of phosphorylation by specific kinases to be determined independent of other kinase activities. Erythrocyte membranes will also be used to determine the differences between ethanol sensitivity of adenosine transport in actively drinking alcoholics and controls. Such studies may provide a test to identify actively drinking alcoholics as well as lead to an understanding of how the transporter is abnormally regulated in cells from alcoholics. In addition, since inhibition of nucleoside uptake by ethanol is the initial step in a cascade of events leading to the chronic effects of ethanol on cAMP signalling, these experiments might lead to new therapies to prevent these chronic effects.

Agency
National Institute of Health (NIH)
Institute
National Institute on Alcohol Abuse and Alcoholism (NIAAA)
Type
Research Project (R01)
Project #
1R01AA010039-01A1
Application #
2046476
Study Section
Special Emphasis Panel (SRCA (52))
Project Start
1995-02-01
Project End
2000-01-31
Budget Start
1995-02-01
Budget End
1996-01-31
Support Year
1
Fiscal Year
1995
Total Cost
Indirect Cost
Name
Ernest Gallo Clinic and Research Center
Department
Type
DUNS #
173995366
City
Emeryville
State
CA
Country
United States
Zip Code
94608
Yao, Lina; Fan, Peidong; Jiang, Zhan et al. (2003) Addicting drugs utilize a synergistic molecular mechanism in common requiring adenosine and Gi-beta gamma dimers. Proc Natl Acad Sci U S A 100:14379-84
Yao, Lina; Arolfo, Maria Pia; Dohrman, Douglas P et al. (2002) betagamma Dimers mediate synergy of dopamine D2 and adenosine A2 receptor-stimulated PKA signaling and regulate ethanol consumption. Cell 109:733-43
Dohrman, Douglas P; Chen, Hui-min; Gordon, Adrienne S et al. (2002) Ethanol-induced translocation of protein kinase A occurs in two phases: control by different molecular mechanisms. Alcohol Clin Exp Res 26:407-15
Gordon, A S; Yao, L; Jiang, Z et al. (2001) Ethanol acts synergistically with a D2 dopamine agonist to cause translocation of protein kinase C. Mol Pharmacol 59:153-60
Yao, L; Asai, K; Jiang, Z et al. (2001) Dopamine D2 receptor inhibition of adenylyl cyclase is abolished by acute ethanol but restored after chronic ethanol exposure (tolerance). J Pharmacol Exp Ther 298:833-9
Constantinescu, A; Diamond, I; Gordon, A S (1999) Ethanol-induced translocation of cAMP-dependent protein kinase to the nucleus. Mechanism and functional consequences. J Biol Chem 274:26985-91
Ron, D; Jiang, Z; Yao, L et al. (1999) Coordinated movement of RACK1 with activated betaIIPKC. J Biol Chem 274:27039-46
Gordon, A S; Yao, L; Dohrman, D P et al. (1998) Ethanol alters the subcellular localization of cAMP-dependent protein kinase and protein kinase C. Alcohol Clin Exp Res 22:238S-242S
Gordon, A S; Yao, L; Wu, Z L et al. (1997) Ethanol alters the subcellular localization of delta- and epsilon protein kinase C in NG108-15 cells. Mol Pharmacol 52:554-9