Aspartic acid substitutions in monoamine oxidase-A reveal both catalytic-dependent and -independent influences on cell viability and proliferation

• Published in: Journal of Neural Transmission Vol. 119; no. 11; pp. 1285 - 1294
• Main Authors: Wei, Zelan, Satram-Maharaj, Tamara, Chaharyn, Bradley, Kuski, Kelly, Pennington, Paul R., Cao, Xia, Chlan, Jennifer, Mousseau, Darrell D.
• Format: Journal Article
• Language: English
• Published: Vienna Springer Vienna 01.11.2012; Springer Nature B.V
• Subjects: Analysis of Variance; Animals; Aspartic Acid - metabolism; Basic Neurosciences; bcl-X Protein - metabolism; Bromodeoxyuridine - metabolism; Calcium - pharmacology; Catalysis - drug effects; Cell Line, Transformed; Cell Line, Tumor; Cell Proliferation - drug effects; Cell Survival - drug effects; Cell Survival - genetics; Enzyme Inhibitors - pharmacology; Genetics and Immunology - Original Article; Humans; Imidazoles - pharmacology; Immunoprecipitation; Indexing in process; Medicine; Medicine & Public Health; Mice; Monoamine Oxidase - genetics; Monoamine Oxidase - metabolism; Mutagenesis, Site-Directed - methods; Mutation - genetics; Neuroblastoma - pathology; Neurology; Neurosciences; Oxidative Stress - drug effects; Oxidative Stress - genetics; Proto-Oncogene Proteins c-bcl-2 - metabolism; Psychiatry; Pyridines - pharmacology; Serotonin - pharmacokinetics; Signal Transduction - drug effects; Signal Transduction - genetics; Superoxide Dismutase - metabolism; Superoxide Dismutase-1; Transfection; Tritium - pharmacokinetics; p38 MAP kinase; Monoamine oxidase; p42/44; Alzheimer’s disease; Catalytic dead; Akt; Proliferation; Parkinson’s disease; Cancer
• ISSN: 0300-9564; 1435-1463
• DOI: 10.1007/s00702-012-0779-x

Post-translational influences could underlie the ambiguous roles of monoamine oxidase-A (MAO-A) in pathologies such as depression, cancer and Alzheimer disease. In support of this, we recently demonstrated that the Ca 2+ -sensitive component of MAO-A catalytic activity is inhibited by a pro-survival p38 (MAPK)-dependent mechanism. We substituted three aspartic acid (D) residues in human MAO-A that reside in putative Ca 2+ -binding motifs and overexpressed the individual proteins in the human HEK293 cell line. We assayed the overexpressed proteins for catalytic activity and for their influence on cell viability (using MTT conversion and trypan blue exclusion) and proliferation/DNA synthesis [using bromodeoxyuridine (BrdU) incorporation]. Innate MAO-A catalytic activity (and the capacity for generating hydrogen peroxide) was unaffected by the D61A substitution, but inhibited moderately or completely by the D248A and D328G substitutions, respectively. The Ca 2+ -sensitive activities of wild-type and D248A MAO-A proteins were enhanced by treatment with the selective p38(MAPK) inhibitor, SB203580, but was completely abrogated by the D61A substitution. Monoamine oxidase-A(D61A) was toxic to cells and exerted no effect on cell proliferation, while MAO-A(D248A) was generally comparable to wild-type MAO-A. As expected, the catalytic-dead MAO-A(D328G) was not cytotoxic, but unexpectedly enhanced both MTT conversion and BrdU staining. Variant-dependent changes in Bax and Bcl-2/Bcl-XL protein expression were observed. A different pattern of effects in N2-a cells suggests cell line-dependent roles for MAO-A. A catalytic-dependent mechanism influences MAO-A-mediated cytotoxicity, whereas a catalytic-independent mechanism contributes to proliferation. Context-dependent inputs by either mechanism could underlie the ambiguous pathological contributions of MAO-A.