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Nuclear import of glucokinase in pancreatic beta-cells is mediated by a nuclear localization signal and modulated by SUMOylation

Johansson, Bente Berg; Fjeld, Karianne; Solheim, Marie Holm; Shirakawa, Jun; Zhang, Enming LU ; Keindl, Magdalena; Hu, Jiang; Lindqvist, Andreas LU ; Døskeland, Anne and Mellgren, Gunnar, et al. (2017) In Molecular and Cellular Endocrinology
Abstract

The localization of glucokinase in pancreatic beta-cell nuclei is a controversial issue. Although previous reports suggest such a localization, the mechanism for its import has so far not been identified. Using immunofluorescence, subcellular fractionation and mass spectrometry, we present evidence in support of glucokinase localization in beta-cell nuclei of human and mouse pancreatic sections, as well as in human and mouse isolated islets, and murine MIN6 cells. We have identified a conserved, seven-residue nuclear localization signal (30LKKVMRR36) in the human enzyme. Substituting the residues KK31,32 and RR35,36 with AA led to a loss of its nuclear localization in transfected cells.... (More)

The localization of glucokinase in pancreatic beta-cell nuclei is a controversial issue. Although previous reports suggest such a localization, the mechanism for its import has so far not been identified. Using immunofluorescence, subcellular fractionation and mass spectrometry, we present evidence in support of glucokinase localization in beta-cell nuclei of human and mouse pancreatic sections, as well as in human and mouse isolated islets, and murine MIN6 cells. We have identified a conserved, seven-residue nuclear localization signal (30LKKVMRR36) in the human enzyme. Substituting the residues KK31,32 and RR35,36 with AA led to a loss of its nuclear localization in transfected cells. Furthermore, our data indicates that SUMOylation of glucokinase modulates its nuclear import, while high glucose concentrations do not significantly alter the enzyme nuclear/cytosolic ratio. Thus, for the first time, we provide data in support of a nuclear import of glucokinase mediated by a redundant mechanism, involving a nuclear localization signal, and which is modulated by its SUMOylation. These findings add new knowledge to the functional role of glucokinase in the pancreatic beta-cell.

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publication status
epub
subject
keywords
Beta-cells, Glucokinase, Human islets, MIN6 cells, Nuclear localization signal, Pancreatic islets, SUMOylation
in
Molecular and Cellular Endocrinology
publisher
Elsevier
external identifiers
  • scopus:85021682199
ISSN
0303-7207
DOI
10.1016/j.mce.2017.06.020
language
English
LU publication?
yes
id
47173b42-ee93-44e0-9a15-bf51b968d9a1
date added to LUP
2017-07-20 08:27:06
date last changed
2017-07-21 03:00:02
@article{47173b42-ee93-44e0-9a15-bf51b968d9a1,
  abstract     = {<p>The localization of glucokinase in pancreatic beta-cell nuclei is a controversial issue. Although previous reports suggest such a localization, the mechanism for its import has so far not been identified. Using immunofluorescence, subcellular fractionation and mass spectrometry, we present evidence in support of glucokinase localization in beta-cell nuclei of human and mouse pancreatic sections, as well as in human and mouse isolated islets, and murine MIN6 cells. We have identified a conserved, seven-residue nuclear localization signal (<sup>30</sup>LKKVMRR<sup>36</sup>) in the human enzyme. Substituting the residues KK<sup>31,32</sup> and RR<sup>35,36</sup> with AA led to a loss of its nuclear localization in transfected cells. Furthermore, our data indicates that SUMOylation of glucokinase modulates its nuclear import, while high glucose concentrations do not significantly alter the enzyme nuclear/cytosolic ratio. Thus, for the first time, we provide data in support of a nuclear import of glucokinase mediated by a redundant mechanism, involving a nuclear localization signal, and which is modulated by its SUMOylation. These findings add new knowledge to the functional role of glucokinase in the pancreatic beta-cell.</p>},
  author       = {Johansson, Bente Berg and Fjeld, Karianne and Solheim, Marie Holm and Shirakawa, Jun and Zhang, Enming and Keindl, Magdalena and Hu, Jiang and Lindqvist, Andreas and Døskeland, Anne and Mellgren, Gunnar and Flatmark, Torgeir and Njølstad, Pål Rasmus and Kulkarni, Rohit N. and Wierup, Nils and Aukrust, Ingvild and Bjørkhaug, Lise},
  issn         = {0303-7207},
  keyword      = {Beta-cells,Glucokinase,Human islets,MIN6 cells,Nuclear localization signal,Pancreatic islets,SUMOylation},
  language     = {eng},
  month        = {06},
  publisher    = {Elsevier},
  series       = {Molecular and Cellular Endocrinology},
  title        = {Nuclear import of glucokinase in pancreatic beta-cells is mediated by a nuclear localization signal and modulated by SUMOylation},
  url          = {http://dx.doi.org/10.1016/j.mce.2017.06.020},
  year         = {2017},
}