Spatial control of protein phosphatase 2A (de)methylation.
Reversible methylation of the protein phosphatase 2A catalytic subunit (PP2A(C)(1)) is an important regulatory mechanism playing a crucial role in the selective recruitment of regulatory B subunits. Here, we investigated the subcellular localization of leucine carboxyl methyltransferase (LCMT1) and protein phosphatase methylesterase (PME-1), the two enzymes catalyzing this process. The results show that PME-1 is predominantly localized in the nucleus and harbors a functional nuclear localization signal, whereas LCMT1 is underrepresented in the nucleus and mainly localizes to the cytoplasm, Golgi region and late endosomes. Indirect immunofluorescence with methylation-sensitive anti-PP2A(C) antibodies revealed a good correlation with the methylation status of PP2A(C), demethylated PP2A(C) being substantially nuclear. Throughout mitosis, demethylated PP2A(C) is associated with the mitotic spindle and during cytokinesis with the cleavage furrow. Overexpression of PME-1, but not of an inactive mutant, results in increased demethylation of PP2A(C) in the nucleus, whereas overexpression of a cytoplasmic PME-1 mutant lacking the NLS results in increased demethylation in the cytoplasm-in all cases, however, without any obvious functional consequences. PME-1 associates with an inactive PP2A population, regardless of its esterase activity or localization. We propose that stabilization of this inactive, nuclear PP2A pool is a major in vivo function of PME-1.
Longin
Sari
S
Department of Molecular Cell Biology, Faculty of Medicine, KU Leuven, Herestraat 49 bus 901, B-3000 Leuven, Belgium.
Zwaenepoel
Karen
K
Martens
Ellen
E
Louis
Justin V
JV
Rondelez
Evelien
E
Goris
Jozef
J
Janssens
Veerle
V
D021581:Active Transport, Cell Nucleus / Q000502:physiology; D000818:Animals; D019556:COS Cells; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism*; D002451:Cell Compartmentation / Q000502:physiology*; D002467:Cell Nucleus / Q000201:enzymology* / Q000648:ultrastructure; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000201:enzymology* / Q000648:ultrastructure; D011992:Endosomes / Q000201:enzymology / Q000648:ultrastructure; D006056:Golgi Apparatus / Q000201:enzymology / Q000648:ultrastructure; D006367:HeLa Cells; D006801:Humans; D008745:Methylation; D008938:Mitosis / Q000502:physiology; D019913:Nuclear Localization Signals; D011497:Protein O-Methyltransferase / Q000378:metabolism; D054648:Protein Phosphatase 2 / Q000737:chemistry / Q000378:metabolism*; D021381:Protein Transport / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D008941:Spindle Apparatus / Q000378:metabolism