GCK-MODY diabetes associated with protein misfolding, cellular self-association and degradation

Biochim Biophys Acta. 2012 Nov;1822(11):1705-15. doi: 10.1016/j.bbadis.2012.07.005. Epub 2012 Jul 20.


GCK-MODY, dominantly inherited mild fasting hyperglycemia, has been associated with >600 different mutations in the glucokinase (GK)-encoding gene (GCK). When expressed as recombinant pancreatic proteins, some mutations result in enzymes with normal/near-normal catalytic properties. The molecular mechanism(s) of GCK-MODY due to these mutations has remained elusive. Here, we aimed to explore the molecular mechanisms for two such catalytically 'normal' GCK mutations (S263P and G264S) in the F260-L270 loop of GK. When stably overexpressed in HEK293 cells and MIN6 β-cells, the S263P- and G264S-encoded mutations generated misfolded proteins with an increased rate of degradation (S263P>G264S) by the protein quality control machinery, and a propensity to self-associate (G264S>S263P) and form dimers (SDS resistant) and aggregates (partly Triton X-100 insoluble), as determined by pulse-chase experiments and subcellular fractionation. Thus, the GCK-MODY mutations S263P and G264S lead to protein misfolding causing destabilization, cellular dimerization/aggregation and enhanced rate of degradation. In silico predicted conformational changes of the F260-L270 loop structure are considered to mediate the dimerization of both mutant proteins by a domain swapping mechanism. Thus, similar properties may represent the molecular mechanisms for additional unexplained GCK-MODY mutations, and may also contribute to the disease mechanism in other previously characterized GCK-MODY inactivating mutations.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Diabetes Mellitus, Type 2 / genetics*
  • Diabetes Mellitus, Type 2 / metabolism
  • Glucokinase* / chemistry
  • Glucokinase* / genetics
  • Glucokinase* / metabolism
  • HEK293 Cells
  • Humans
  • Mutant Proteins* / chemistry
  • Mutant Proteins* / genetics
  • Mutant Proteins* / metabolism
  • Mutation
  • Octoxynol
  • Protein Conformation
  • Protein Folding
  • Protein Multimerization
  • Proteolysis
  • Proteostasis Deficiencies* / genetics
  • Proteostasis Deficiencies* / metabolism
  • Reticulocytes / metabolism


  • Mutant Proteins
  • Octoxynol
  • Glucokinase