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Expression and intracellular localization of catechol O-methyltransferase in transfected mammalian cells

Ulmanen, Ismo; Peränen, Johan; Tenhunen, Jukka; Tilgmann, Carola LU ; Karhunen, Tuula; Panula, Pertti; Bernasconi, Lilia; Aubry, Jean Piere and Lundström, Kenneth (1997) In European Journal of Biochemistry 243(1-2). p.452-459
Abstract

The intracellular localization of soluble and membrane-bound isoforms of rat and human catechol O-methyltransferase (COMT) was studied by expressing the recombinant COMT proteins either separately or together in mammalian cell lines (HeLa and COS-7 cells) and in rat primary neurons. The distribution of soluble and membrane-bound COMT enzyme was visualized by immunocytochemistry. For comparison, the localization of native COMT was studied in rat C6 glioma cells by immunoelectron microscopy. Staining of cells expressing membrane-bound COMT with a COMT-specific antiserum revealed an immunofluorescence signal in intracellular reticular structures and in the nuclear membrane. Double-staining of the cells with antisera against proteins... (More)

The intracellular localization of soluble and membrane-bound isoforms of rat and human catechol O-methyltransferase (COMT) was studied by expressing the recombinant COMT proteins either separately or together in mammalian cell lines (HeLa and COS-7 cells) and in rat primary neurons. The distribution of soluble and membrane-bound COMT enzyme was visualized by immunocytochemistry. For comparison, the localization of native COMT was studied in rat C6 glioma cells by immunoelectron microscopy. Staining of cells expressing membrane-bound COMT with a COMT-specific antiserum revealed an immunofluorescence signal in intracellular reticular structures and in the nuclear membrane. Double-staining of the cells with antisera against proteins specific for the rough endoplasmic reticulum indicated that they colocalized with membrane bound COMT, suggesting that it resided in the endoplasmic reticulum. Notably, no COMT-specific fluorescence of plasma membranes was detected. The signal in the endoplasmic reticulum was also evident in the cells expressing both recombinant COMT forms. Intracellular native COMT reaction was detected by immunoelectron microscopy in rat C6 glioma cells and an intense cytoplasmic signal was seen in the primary neurons infected with the recombinant Semliki Forest virus. The cells expressing recombinant soluble COMT revealed intense nuclear staining together with diffuse cytoplasmic immunoreactivity, suggesting that a parr of soluble COMT is transported to nuclei. Western blotting from rat liver and brain revealed soluble COMT in the nuclei. Enzyme activity measurements from liver cytoplasmic and nuclear fractions suggested that about 5% of the soluble COMT resided in nuclei. The intracellular localization of both COMT forms implies that COMT acts in the cytoplasm and possibly also in the nuclear compartment, and that the physiological substrates of COMT enzymes may have to be internalized before their methylation by COMT.

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author
publishing date
type
Contribution to journal
publication status
published
keywords
Catecholamine, Immunocytochemistry, Nucleus, Recombinant protein, Rough endoplasmic reticulum
in
European Journal of Biochemistry
volume
243
issue
1-2
pages
8 pages
publisher
Wiley-Blackwell
external identifiers
  • Scopus:0031037713
ISSN
0014-2956
language
English
LU publication?
no
id
fd80247f-de37-4a62-9b46-0a4bb9829eb0
date added to LUP
2016-04-11 13:17:22
date last changed
2016-07-27 09:35:17
@misc{fd80247f-de37-4a62-9b46-0a4bb9829eb0,
  abstract     = {<p>The intracellular localization of soluble and membrane-bound isoforms of rat and human catechol O-methyltransferase (COMT) was studied by expressing the recombinant COMT proteins either separately or together in mammalian cell lines (HeLa and COS-7 cells) and in rat primary neurons. The distribution of soluble and membrane-bound COMT enzyme was visualized by immunocytochemistry. For comparison, the localization of native COMT was studied in rat C6 glioma cells by immunoelectron microscopy. Staining of cells expressing membrane-bound COMT with a COMT-specific antiserum revealed an immunofluorescence signal in intracellular reticular structures and in the nuclear membrane. Double-staining of the cells with antisera against proteins specific for the rough endoplasmic reticulum indicated that they colocalized with membrane bound COMT, suggesting that it resided in the endoplasmic reticulum. Notably, no COMT-specific fluorescence of plasma membranes was detected. The signal in the endoplasmic reticulum was also evident in the cells expressing both recombinant COMT forms. Intracellular native COMT reaction was detected by immunoelectron microscopy in rat C6 glioma cells and an intense cytoplasmic signal was seen in the primary neurons infected with the recombinant Semliki Forest virus. The cells expressing recombinant soluble COMT revealed intense nuclear staining together with diffuse cytoplasmic immunoreactivity, suggesting that a parr of soluble COMT is transported to nuclei. Western blotting from rat liver and brain revealed soluble COMT in the nuclei. Enzyme activity measurements from liver cytoplasmic and nuclear fractions suggested that about 5% of the soluble COMT resided in nuclei. The intracellular localization of both COMT forms implies that COMT acts in the cytoplasm and possibly also in the nuclear compartment, and that the physiological substrates of COMT enzymes may have to be internalized before their methylation by COMT.</p>},
  author       = {Ulmanen, Ismo and Peränen, Johan and Tenhunen, Jukka and Tilgmann, Carola and Karhunen, Tuula and Panula, Pertti and Bernasconi, Lilia and Aubry, Jean Piere and Lundström, Kenneth},
  issn         = {0014-2956},
  keyword      = {Catecholamine,Immunocytochemistry,Nucleus,Recombinant protein,Rough endoplasmic reticulum},
  language     = {eng},
  number       = {1-2},
  pages        = {452--459},
  publisher    = {ARRAY(0x7f59b18)},
  series       = {European Journal of Biochemistry},
  title        = {Expression and intracellular localization of catechol O-methyltransferase in transfected mammalian cells},
  volume       = {243},
  year         = {1997},
}