p38(MAPK) Negatively Regulates Monoamine Oxidase-A Activity As Well As Its Sensitivity To Ca2+.

by Cao, Xia

Monoamine oxidase (MAO) is a mitochondrial deaminating enzyme that exists as two isoforms, MAO-A and -B. The MAO-mediated reaction generates hydrogen peroxide (H2O2) as a normal by-product. Dysregulation of MAO has been implicated in a variety of neuropsychiatric and neurodegenerative disorders, as well as in the aging process. Endogenous regulators of MAO-A function include calcium (Ca2+) and the p38 mitogen-activated protein kinase (MAPK). Although the effect of p38(MAPK) is thought to rely on induction of mao-A gene expression, post-translational modification of the MAO-A protein is also possible.

Using standard biochemical approaches in combination with pharmacological interventions and recombinant DNA strategies, specific aspartic acid residues (within putative Ca2+-binding motifs) were demonstrated to contribute to MAO-A activity. Furthermore, MAO-A activity and its sensitivity to Ca2+ was negatively regulated by the p38(MAPK), which is usually activated during cell stress. The effect of p38(MAPK) on MAO-A function relies specifically on Serine209 in MAO-A, which resides in a p38(MAPK) consensus motif. The serine phosphorylation status of MAO-A determines its capacity for generating peroxy radicals and its toxicity in established cell lines (e.g. C6, N2a, HEK293A, HT-22) and in primary cortical neurons. p38(MAPK)-regulated MAO-A activity is also linked to neurotoxicity associated with the Alzheimer disease-related peptide, Ò-amyloid (AÒ). These data suggest a unique neuroprotective role for p38(MAPK) centered on a negative feedback regulation of the Ca2+-sensitive, H2O2-generating enzyme MAO-A.