Protein expression changes in a cell system of beta-cell maturation reflect an acquired sensitivity to IL-1beta.
OBJECTIVE
Type 1 diabetes mellitus (T1DM) is caused by specific destruction of the pancreatic beta cells in the islets of Langerhans. Increased sensitivity to cytokines, in particular to interleukin-1beta (IL-1beta) seems to be an acquired trait during beta-cell maturation. In response to cytokines both protective and deleterious mechanisms are induced in beta cells, and when the deleterious prevail, T1DM develops. The aims of this study were to identify perturbation in protein patterns (PiPP) associated with beta-cell maturation, and compare these changes to previous analyses of IL-1beta exposed rat islets. For this purpose, proteome analyses were carried out using a cell-line, which matures from a glucagon-producing pre-beta-cell phenotype (NHI-glu) to an insulin-producing beta-cell phenotype (NHI-ins). We have previously shown that this maturation is accompanied by acquired sensitivity to the toxic effects of IL-1beta.


METHODS
2D-gel electrophoresis was used to separate the proteins and MALDI-MS and database searches were performed to identify the proteins.


RESULTS
During beta-cell maturation 135 protein spots out of 2239 detectable changed expression levels. Of these, 74 were down-regulated, 44 up-regulated, 16 were suppressed and 1 was expressed de novo. Using MALDI-MS, positive identification was obtained for 93 out of the 135 protein-spots revealing 97 different proteins. Of these, 22 proteins were in common with changes identified in previous proteome analysis of perturbation in protein pattern in IL-1beta exposed rat islets. Several of the proteins were present in more than one spot suggesting post-translational modification.


CONCLUSIONS
Several proteins and protein modifications were identified that could be critically involved in beta-cell maturation, insulin-gene expression and the acquired IL-1beta sensitivity.
Nielsen
K
K
Steno Diabetes Center, Niels Steensensvej 2, 2820 Gentofte, Denmark.
Sparre
T
T
Larsen
M R
MR
Nielsen
M
M
Fey
S J
SJ
Mose Larsen
P
P
Roepstorff
P
P
Nerup
J
J
Karlsen
A E
AE
D000818:Animals; D002478:Cells, Cultured; D015180:Electrophoresis, Gel, Two-Dimensional; D004734:Energy Metabolism; D005786:Gene Expression Regulation / Q000187:drug effects*; D005982:Glutathione Transferase / Q000378:metabolism; D006019:Glycolysis; D007375:Interleukin-1 / Q000494:pharmacology*; D007515:Islets of Langerhans / Q000187:drug effects / Q000502:physiology*; D008715:Methionine / Q000378:metabolism; D010084:Oxidation-Reduction; D014176:Protein Biosynthesis; D017510:Protein Folding; D011506:Proteins / Q000235:genetics / Q000302:isolation & purification; D051381:Rats; D011919:Rats, Inbred Strains; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D007375:Interleukin-1; D011506:Proteins; D008715:Methionine; D005982:Glutathione Transferase