Molecular mechanism of alcoholism : Ethanol and cell signaling

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Alcoholism induces serious functional and pathological abnormalities in many organs, particularly in the central nervous system. However, the molecular mechanisms accounting for these effects have not been identified, because ethanol can affect many different receptors and transpoters on the cell membrane. Recent studies suggest ethanol can modify intracellular signal transduction systems. We have proposed NG108-15, neuronal cultured cells as a model, and we have found that cAMP system is involved in the induction of heterologous desensitization, an example of ethanol tolerance at a cellular level. In the present project, we have established NG108-15 cells expressing transmitter receptors by stable transfection to identify receptors of which signal transduction system could be modified by chronic ethanol.At first, we checked the effect of chronic ethanol on promotor activity. We chose CMV,RSV and SV40 promotors and assessed the changes of these activeties using receptor binding assays … More or CAT assay. In NG108 cells transiently expressing CAT,chronic ethanol activated the activities of all promotors. However, chronic ethanol treatment did not change the expression of A_1 or D_2 receptors or CAT in some stable transfectants. These finding suggest not only promotors, but also cis elements juxtaposing with inserted cDNA would affect the effect of ethanol on the gene expresion.In our previous study, adenosine A_2 receptor is attributed to the generation of heterologous desensitization by accumulating extracellular adenosine after chronic ethanol treatment, but A_1 receptor seems not to be involved in the induction of these phenomenon.Protein Kinases play important roles in the intracellular signal transduction system and the translocation of these kinases is accompanied with these activation. So we focused on the translocation of protein kinases, especially A kinase (PDA) and C kinase (PKC), induced by ethanol. In NG108 cells, ethanol translocated catalytic subunit of PKA from cytosol to nucleus, but RI,a regulatory subunit of PKA was not translocated. Also, ethanol translocated some isozymes of PKC in NG108 cells. We will perform further studies on those translocations by chronic ethanol. Less