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.
(Less)
- author
- Ulmanen, Ismo
; Peränen, Johan
; Tenhunen, Jukka
; Tilgmann, Carola
LU
; Karhunen, Tuula
; Panula, Pertti
; Bernasconi, Lilia
; Aubry, Jean Piere
and Lundström, Kenneth
- publishing date
- 1997
- 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
- pmid:9030772
- 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
- 2024-04-04 17:43:43
@article{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}},
keywords = {{Catecholamine; Immunocytochemistry; Nucleus; Recombinant protein; Rough endoplasmic reticulum}},
language = {{eng}},
number = {{1-2}},
pages = {{452--459}},
publisher = {{Wiley-Blackwell}},
series = {{European Journal of Biochemistry}},
title = {{Expression and intracellular localization of catechol O-methyltransferase in transfected mammalian cells}},
volume = {{243}},
year = {{1997}},
}