Expression of protein phosphatase 2A mutants and silencing of the regulatory B[alpha] subunit induce a selective loss of acetylated and detyrosinated microtubules

• Published in: Journal of neurochemistry Vol. 101; no. 4; p. 959
• Main Authors: Nunbhakdi-Craig, Viyada, Schuechner, Stefan, Sontag, Jean-Marie, Montgomery, Lisa, Pallas, David C, Juno, Claudia, Mudrak, Ingrid, Ogris, Egon, Sontag, Estelle
• Format: Journal Article
• Language: English
• Published: New York Blackwell Publishing Ltd 01-05-2007
• Subjects: Alzheimer's disease; Cellular biology; Cytoskeleton; Enzymes; Gene expression; Neurosciences; Proteins
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1111/j.1471-4159.2007.04503.x

Carboxymethylation and phosphorylation of protein phosphatase 2A (PP2A) catalytic C subunit are evolutionary conserved mechanisms that critically control PP2A holoenzyme assembly and substrate specificity. Down-regulation of PP2A methylation and PP2A enzymes containing the Balpha regulatory subunit occur in Alzheimer's disease. In this study, we show that expressed wild-type and methylation- (L309Delta) and phosphorylation- (T304D, T304A, Y307F, and Y307E) site mutants of PP2A C subunit differentially bind to B, B', and B''-type regulatory subunits in NIH 3T3 fibroblasts and neuro-2a (N2a) neuroblastoma cells. They also display distinct binding affinity for microtubules (MTs). Relative to controls, expression of the wild-type, T304A and Y307F C subunits in N2a cells promotes the accumulation of acetylated and detyrosinated MTs. However, expression of the Y307E, L309Delta, and T304D mutants, which are impaired in their ability to associate with the alpha subunit, induces their loss. Silencing of Balpha subunit in N2a and NIH 3T3 cells is sufficient to induce a similar breakdown of acetylated and detyrosinated MTs. It also confers increased sensitivity to nocodazole-induced MT depolymerization. Our findings suggest that changes in intracellular PP2A subunit composition can modulate MT dynamics. They support the hypothesis that reduced amounts of neuronal Balpha-containing PP2A heterotrimers contribute to MT destabilization in Alzheimer's disease. [PUBLICATION ABSTRACT]