INFLUENCE OF ENTHALNOL ON MITOCHONDRIAL PROTEIN IMPORT

The hypothesis proposed in these investigations is that ethanol
consumption impairs the transport of precursor proteins into the
mitochondrion, and therefore affects mitochondrial function and
assembly. The experiments proposed will seek to determine 1) if
ethanol and acetaldehyde can directly affect the ability of
hepatic mitochondria to import and process a specific precursor
protein and 2) if chronic ethanol administration affects the import
and processing activity of isolated liver mitochondria. The
methodology proposed is the use of an in vitro
translation/mitochondrial import assay in which radioactive
proteins will first be synthesized in vitro using lysates of rabbit
reticulocytes programmed with rat liver RNA. The radiolabelled
translation products will then be incubated with isolated rat liver
mitochondria and, the import and processing of proteins in general
and, in particular, of the mitochondrial enzyme glutamate
dehydrogenase (GDH), will be measured. The latter assay will
determine the amount of higher molecular weight precursor GDH
that is converted to the mature, lower molecular weight form of
the enzyme. These experiments specifically seek to determine
whether mitochondrial import is impaired by ethanol consumption
and whether this may contribute to the ethanol-induced
abnormalities in mitochondrial structure and function reported by
others. Alcohol-induced impairment of normal mitochondrial
function may contribute to the pathogenesis of alcoholic liver
disease since many other energy-requiring cellular activities are
dependent on normal mitochondrial energy generation. If
mitochondrial import is shown to be altered by ethanol and/or
acetaldehyde in the proposed experiments, it will be one of the
first direct demonstrations of a mechanism which may explain
how ethanol consumption can significantly alter the structure and
function of this organelle.