The effect of alcohol consumption on drug metabolism and interactions of alcohol with drugs constitute a significant health problem. The mechanisms of these effects are tightly related to the influence of alcohol on drug- metabolizing system, and on cytochrome P450 ensemble in particular. Functional versatility of the cytochrome P450 system is achieved through the presence of over a dozen of P450 species differing in their substrate specificity. The composition of this ensemble is known to be largely affected by alcohol consumption. It is generally presumed that the integral properties of this ensemble represent a simple aggregate of the properties of the constituting P450 enzymes. Although this premise remains to be a foundation of rational analysis of the routes of drug metabolism, its validity became essentially compromised. The body of evidence of system-wide integration in the properties of the P450 ensemble continues to grow. The current project is prompted by recognition of a far-reaching physiological significance and pharmacological importance of inter-species crosstalk in the P450 ensemble and its thorough relevance to the effects of alcohol on drug metabolism and P450- dependent cellular signaling. Our central hypothesis is that the results of the alcohol-induced changes in the composition of the cytochrome P450 pool are not limited to direct consequences of the activity of the alcohol-induced enzymes. They also involve alterations of the metabolism of a broad range of exogenous and endogenous substrates of various P450 enzymes due to their interactions with alcohol-inducible P450 species. These indirect effects are deeply involved in clinically-important cases of alcohol interactions with drugs and alcohol-induced alteration of cellular signaling through eicosanoids, retinoic acid and other P450-dependent messengers. This proposal is aimed to explore the alcohol-induced changes in P450 expression and their effects of on the network of protein-protein interaction in the ER membranes and, consequently, on the system-wide properties of the P450 ensemble. Our long-term goal is to obtain a complete picture of functional interactions between human cytochromes P450, and the alcohol-inducible P450 species in particular, and characterize their role in dictating the integral properties of the drug-metabolizing ensemble and their changes by alcohol consumption. Specific Aims of the project are: (1) To refine our knowledge on alcohol-induced changes in the composition of the cytochrome P450 ensemble in liver cells; (2) To identify the principal intermolecular interactions of alcohol- induced P450 species in HLM; (3) To identify the major functional interactions of alcohol-inducible P450 enzymes with other P450 species and explore their effect on the metabolism of drugs and endogenous substrates by the P450 ensemble. Fulfilling these aims will allow in-depth characterization of alcohol-induced changes in drug-metabolism and P450-dependent cellu...