The brain energy metabolism is met primarily in mitochondria by oxidative metabolism of pyruvate, which is regulated by pyruvate dehydrogenase complex (PDHC). The PDHC is controlled by a kinase-phosphatase mediated phosphorylation (inactivation) and dephosphorylation (activation) process. Deficits of PDHC have been found in an increasing number of neurological disorders, including Alzheimer's disease. Changes of phosphorylation or activation state of PDHC have also been found to accompany many physiological, pharmacological and behavioral manipulations that give rise to altered brain functions. These changes of PDHC may reflect changes of pyruvate oxidation or Ca sequestration by mitochondria. The molecular events underlying these changes are unclear, however. To this end, the relationship among PDHC regulatory behavior, pyruvate ovidation and mitochondrial Ca sequestration will be delineated in this proposition. The mitochondrial Ca-uptake process is distinct from the effect of intramitochondrially accumulated Ca. The effects of these two processes on pyruvate oxidation and PDHC phosphorylation will be evaluated, using mitochondria treated with ionophore A23187 in Ca-EGTA buffer and mitochonria pre-loaded or depleted with Ca, respectively. With respect to enzyme protein, PDHC may be regulated by phosphorylation at multiple sites and by protein translation during postnatal development. The significance of multiple phosphorylation will be evaluated by comparing the phosphate profile of the phosphopeptide generated by immunoprecipitation and 2-dimensional gel electrophoresis. The enzyme induction mechanism will be tested by radioimmunoassays and in vivo translation assays of the PDHC-peptides. Aging decreases pyruvate oxidation and Ca metabolism. To further test the hypothesis that mitochondrial Ca sequestration is also imparied in aging, the Ca buffering capacity, and Ca uptake and its coupling to pyruvate oxidation and possible link to PDHC phosphorylation will be comared in mitochondria from different age groups.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
1R01NS022952-01
Application #
3405804
Study Section
Neurological Sciences Subcommittee 1 (NLS)
Project Start
1986-02-01
Project End
1989-01-31
Budget Start
1986-02-01
Budget End
1987-01-31
Support Year
1
Fiscal Year
1986
Total Cost
Indirect Cost
Name
Burke Rehabilitation Center (White Plns,NY)
Department
Type
DUNS #
City
White Plains
State
NY
Country
United States
Zip Code
10605
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Sheu, K F; Szabo, P; Ko, L W et al. (1989) Abnormalities of pyruvate dehydrogenase complex in brain disease. Ann N Y Acad Sci 573:378-91
Lai, J C; DiLorenzo, J C; Sheu, K F (1988) Pyruvate dehydrogenase complex is inhibited in calcium-loaded cerebrocortical mitochondria. Neurochem Res 13:1043-8
Lai, J C; Sheu, K F (1987) The effect of 2-oxoglutarate or 3-hydroxybutyrate on pyruvate dehydrogenase complex in isolated cerebrocortical mitochondria. Neurochem Res 12:715-22