title: Expression of protein phosphatase 2A mutants and silencing of the regulatory B alpha subunit induce a selective loss of acetylated and detyrosinated microtubules.
abstract: 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 B alpha regulatory subunit occur in Alzheimer's disease. In this study, we show that expressed wild-type and methylation- (L309 Delta) 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, L309 Delta, and T304D mutants, which are impaired in their ability to associate with the B alpha subunit, induces their loss. Silencing of B alpha 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 B alpha-containing PP2A heterotrimers contribute to MT destabilization in Alzheimer's disease.
authors: Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9073, USA.
authors: Viyada
authors: V
authors: Nunbhakdi-Craig
authors: Stefan
authors: S
authors: Schuechner
authors: Jean-Marie
authors: JM
authors: Sontag
authors: Lisa
authors: L
authors: Montgomery
authors: David C
authors: DC
authors: Pallas
authors: Claudia
authors: C
authors: Juno
authors: Ingrid
authors: I
authors: Mudrak
authors: Egon
authors: E
authors: Ogris
authors: Estelle
authors: E
authors: Sontag
mesh_terms: D000107:Acetylation; D000818:Animals; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics*; D051379:Mice; D008870:Microtubules / Q000378:metabolism*; D009154:Mutation / Q000502:physiology*; D009447:Neuroblastoma; D019319:Okadaic Acid / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000378:metabolism*; D054648:Protein Phosphatase 2; D034622:RNA Interference / Q000502:physiology; D014162:Transfection / Q000379:methods; D014443:Tyrosine / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D019319:Okadaic Acid; D014443:Tyrosine; D010749:Phosphoprotein Phosphatases; C117094:Ppp2r3a protein, mouse; D054648:Protein Phosphatase 2