Effects of ethanol on phosphorylation of lipids in rat synaptic plasma membranes

Alcohol modulation of G-protein-gated inwardly rectifying potassium channels: from binding to therapeutics

Alcohol (ethanol)-induced behaviors may arise from direct interaction of alcohol with discrete protein cavities within brain proteins. Recent structural and biochemical studies have provided new insights into the mechanism of alcohol-dependent activation of G protein-gated inwardly rectifying potassium (GIRK) channels, which regulate neuronal responses in the brain reward circuit. GIRK channels contain an alcohol binding pocket formed at the interface of two adjacent channel subunits. Here, we discuss the physiochemical properties of the alcohol pocket and the roles of G protein βγ subunits and membrane phospholipid PIP2 in regulating the alcohol response of GIRK channels. Some of the features of alcohol modulation of GIRK channels may be common to other alcohol-sensitive brain proteins. We discuss the possibility of alcohol-selective therapeutics that block alcohol access to the pocket. Understanding alcohol recognition and modulation of brain proteins is essential for development of therapeutics for alcohol abuse and addiction.

Molecular mechanism underlying ethanol activation of G-protein-gated inwardly rectifying potassium channels

Alcohol (ethanol) produces a wide range of pharmacological effects on the nervous system through its actions on ion channels. The molecular mechanism underlying ethanol modulation of ion channels is poorly understood. Here we used a unique method of alcohol-tagging to demonstrate that alcohol activation of a G-protein-gated inwardly rectifying potassium (GIRK or Kir3) channel is mediated by a defined alcohol pocket through changes in affinity for the membrane phospholipid signaling molecule phosphatidylinositol 4,5-bisphosphate. Surprisingly, hydrophobicity and size, but not the canonical hydroxyl, were important determinants of alcohol-dependent activation. Altering levels of G protein Gβγ subunits, conversely, did not affect alcohol-dependent activation, suggesting a fundamental distinction between receptor and alcohol gating of GIRK channels. The chemical properties of the alcohol pocket revealed here might extend to other alcohol-sensitive proteins, revealing a unique protein microdomain for targeting alcohol-selective therapeutics in the treatment of alcoholism and addiction.

Energy consumption by phospholipid metabolism in mammalian brain

Until recently, brain phospholipid metabolism was thought to consume only 2% of the ATP consumed by the mammalian brain as a whole. In this paper, however, we calculate that 1.4% of total brain ATP consumption is consumed for the de novo synthesis of ether phospholipids and that another 5% is allocated to the phosphatidylinositide cycle. When added to previous estimates that fatty acid recycling within brain phospholipids and maintenance of membrane lipid asymmetries of acidic phospholipids consume, respectively, 5% and 8% of net brain ATP consumption, it appears that phospholipid metabolism can consume up to 20% of net brain ATP consumption. This new estimate is consistent with recent evidence that phospholipids actively participate in brain signaling and membrane remodeling, among other processes.

Induction of in vitro angiogenesis in the endothelial-derived cell line, EA hy926, by ethanol is mediated through PKC and MAPK

We have previously shown that ethanol-induced injury to the gastric mucosa triggers increased expression of the angiogenic factors, basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) and angiogenesis. To further investigate ethanol-induced angiogenesis, we used an in vitro angiogenesis model which employs the ability of an endothelial-derived cell line (EA hy926) to form tubelike structures resembling capillaries when plated on the matrix material, Matrigel. We report that serum-starved EA hy926 cells, incubated for as little as 5 minutes with ethanol concentrations of 1.0-2.5%, formed tubelike structures reflecting in vitro angiogenesis. Control cells, not incubated with ethanol, did not form tubelike structures. Incubation for 5 minutes with 2.5% ethanol resulted in increased activities of PKC and MAP kinase (ERK2) by 1.6-fold (p < 0.05) and 2.3-fold (P < 0.001), respectively. Furthermore, inhibitors of the MAPK kinase, MEK (PD98059) and PKC (GF 109203X) prevented the induction of in vitro angiogenesis by ethanol.