Regulation of protein phosphatase 2A methylation by LCMT1 and PME-1 plays a critical role in differentiation of neuroblastoma cells.
Neuritic alterations are a major feature of many neurodegenerative disorders. Methylation of protein phosphatase 2A (PP2A) catalytic C subunit by the leucine carboxyl methyltransferase (LCMT1), and demethylation by the protein phosphatase methylesterase 1, is a critical PP2A regulatory mechanism. It modulates the formation of PP2A holoenzymes containing the Bα subunit, which dephosphorylate key neuronal cytoskeletal proteins, including tau. Significantly, we have reported that LCMT1, methylated C and Bα expression levels are down-regulated in Alzheimer disease-affected brain regions. In this study, we show that enhanced expression of LCMT1 in cultured N2a neuroblastoma cells, which increases endogenous methylated C and Bα levels, induces changes in F-actin organization. It promotes serum-independent neuritogenesis and development of extended tau-positive processes upon N2a cell differentiation. These stimulatory effects can be abrogated by LCMT1 knockdown and S-adenosylhomocysteine, an inhibitor of methylation reactions. Expression of protein phosphatase methylesterase 1 and the methylation-site L309Δ C subunit mutant, which decrease intracellular methylated C and Bα levels, block N2a cell differentiation and LCMT1-mediated neurite formation. Lastly, inducible and non-inducible knockdown of Bα in N2a cells inhibit process outgrowth. Altogether, our results establish a novel mechanistic link between PP2A methylation and development of neurite-like processes.
School of Biomedical Sciences and Pharmacy, Faculty of Health, The University of Newcastle, Callaghan, NSW, Australia. estelle.sontag@newcastle.edu.au
Jean-Marie
JM
Sontag
Viyada
V
Nunbhakdi-Craig
Martina
M
Mitterhuber
Egon
E
Ogris
Estelle
E
Sontag
D000818:Animals; D002265:Carboxylic Ester Hydrolases / Q000502:physiology*; D020134:Catalytic Domain / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology*; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D019175:DNA Methylation / Q000235:genetics / Q000502:physiology*; D055785:Gene Knockdown Techniques; D051379:Mice; D016501:Neurites / Q000201:enzymology / Q000473:pathology; D009447:Neuroblastoma / Q000201:enzymology* / Q000235:genetics / Q000473:pathology*; D011497:Protein O-Methyltransferase / Q000502:physiology; D054648:Protein Phosphatase 2 / Q000502:physiology*
C524761:LCMT1 protein, human; C586068:Lcmt1 protein, mouse; D011497:Protein O-Methyltransferase; D002265:Carboxylic Ester Hydrolases; C119357:protein phosphatase methylesterase-1; D054648:Protein Phosphatase 2