title: Protein markers for insulin-producing beta cells with higher glucose sensitivity.
abstract: METHODS
  Pancreatic beta cells show intercellular differences in their metabolic glucose sensitivity and associated activation of insulin production. To identify protein markers for these variations in functional glucose sensitivity, rat beta cell subpopulations were flow-sorted for their level of glucose-induced NAD(P)H and their proteomes were quantified by label-free data independent alternate scanning LC-MS. Beta cell-selective proteins were also identified through comparison with rat brain and liver tissue and with purified islet alpha cells, after geometrical normalization using 6 stably expressed reference proteins.
  
  
  RESULTS
  All tissues combined, 943 proteins were reliably quantified. In beta cells, 93 out of 467 quantifiable proteins were uniquely detected in this cell type; several other proteins presented a high molar abundance in beta cells. The proteome of the beta cell subpopulation with high metabolic and biosynthetic responsiveness to 7.5 mM glucose was characterized by (i) an on average 50% higher expression of protein biosynthesis regulators such as 40S and 60S ribosomal constituents, NADPH-dependent protein folding factors and translation elongation factors; (ii) 50% higher levels of enzymes involved in glycolysis and in the cytosolic arm of the malate/aspartate-NADH-shuttle. No differences were noticed in mitochondrial enzymes of the Krebs cycle, beta-oxidation or respiratory chain.
  
  
  CONCLUSIONS
  Quantification of subtle variations in the proteome using alternate scanning LC-MS shows that beta cell metabolic glucose responsiveness is mostly associated with higher levels of glycolytic but not of mitochondrial enzymes.
authors.affiliation: Diabetes Research Center, Brussels Free University (VUB), Brussels, Belgium. geert.martens@vub.ac.be
authors.forename: Geert A
authors.initials: GA
authors.lastname: Martens
authors.forename: Lei
authors.initials: L
authors.lastname: Jiang
authors.forename: Katrijn
authors.initials: K
authors.lastname: Verhaeghen
authors.forename: Joanne B
authors.initials: JB
authors.lastname: Connolly
authors.forename: Scott G
authors.initials: SG
authors.lastname: Geromanos
authors.forename: Geert
authors.initials: G
authors.lastname: Stangé
authors.forename: Laurence
authors.initials: L
authors.lastname: Van Oudenhove
authors.forename: Bart
authors.initials: B
authors.lastname: Devreese
authors.forename: Karine H
authors.initials: KH
authors.lastname: Hellemans
authors.forename: Zhidong
authors.initials: Z
authors.lastname: Ling
authors.forename: Christiaan
authors.initials: C
authors.lastname: Van Schravendijk
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Pipeleers
authors.forename: Johannes P C
authors.initials: JP
authors.lastname: Vissers
authors.forename: Frans K
authors.initials: FK
authors.lastname: Gorus
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D002853:Chromatography, Liquid / Q000379:methods; D005786:Gene Expression Regulation; D005947:Glucose / Q000378:metabolism*; D006019:Glycolysis; D007328:Insulin / Q000096:biosynthesis*; D050417:Insulin-Secreting Cells / Q000166:cytology*; D008099:Liver / Q000378:metabolism; D013058:Mass Spectrometry / Q000379:methods; D008928:Mitochondria / Q000201:enzymology; D020543:Proteome; D040901:Proteomics / Q000379:methods; D051381:Rats; D014018:Tissue Distribution
chemical_list: D007328:Insulin; D020543:Proteome; D005947:Glucose