Abstract
Mitochondrial transcription factor A (TFAM) plays pivotal roles in packaging mitochondrial DNA (mtDNA) and regulating its transcription in mammalian mitochondria. We have previously shown that chronic stress induced by repeated low-dose applications of the complex I inhibitor 1-methyl-4-phenylpyridinium (MPP+) results in impaired biosynthesis of mtDNA-encoded proteins, accompanied by a reduction in TFAM expression. MPP+ - induced mitochondrial dysfunction and TFAM down-regulation was markedly inhibited by U0126, ERK1/2 RNAi or transfection of dominant-negative MEK1. Here, we report that TFAM is post translationally modified by phosphorylation during chronic MPP+ treatment through a mechanism reversed by U0126. In addition, we demonstrate that TFAM is a direct target of ERK2 as assessed in an in vitro kinase reaction, and are characterizing potential phosphorylation sites. Intriguingly, we also observed reduced levels of TFAM in midbrain tissue from a transgenic mouse model of autosomal dominant Parkinson's disease; 2-D immunoblot analysis suggests increased phosphorylation of both TFAM and ERK1/2, suggesting the possibility of common mechanisms in the toxin and genetic models. Further investigations of the biological significance of TFAM phosphorylation may shed light on mechanisms regulating mitochondrial homeostasis and cell fate in response to disease-related cellular stresses.
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