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Author Langer, Sara ♦ Platz, Christian ♦ Waterstradt, Rica ♦ Baltrusch, Simone
Source United States Department of Energy Office of Scientific and Technical Information
Content type Text
Language English
Subject Keyword APPLIED LIFE SCIENCES ♦ COMPARATIVE EVALUATIONS ♦ DRUGS ♦ ENZYMES ♦ FRUCTOSE ♦ GLUCOSE ♦ INSULIN ♦ LIVER ♦ LIVER CELLS ♦ METABOLISM ♦ MUTANTS ♦ MUTATIONS ♦ PANCREAS ♦ PATIENTS ♦ SECRETION ♦ STIMULI ♦ THERAPY
Abstract Glucokinase plays a key role in glucose sensing in pancreatic beta cells and in liver metabolism. Heterozygous inactivating glucokinase mutations cause the autosomal dominantly inherited MODY2 subtype of maturity-onset diabetes of the young. The goal of this study was to elucidate the pathogenicity of the recently described glucokinase mutants L304P and L315H, located in an alpha-helix and connecting region, respectively, at the outer region of the large domain of glucokinase. Both mutants showed wild-type-like cytosolic localization, but faster protein degradation in insulin-secreting MIN6 cells. However, strongly reduced nuclear/cytoplasmic localization of the mutants was observed in primary hepatocytes suggesting reduced interaction with the liver specific glucokinase regulatory protein. Both mutants displayed a significantly lowered glucokinase activity compared to the wild-type protein. Even though the L315H protein showed the lowest enzymatic activity, this mutant was very sensitive to allosteric activation. The endogenous activator fructose-2,6-bisphosphatase evoked an increase in glucokinase activity for both mutants, but much stronger for L315H compared to L304P. The synthetic activator RO281675 was ineffective against the L304P mutant. Expression of the mutant proteins evoked loss of glucose-induced insulin secretion in MIN6 cells. Administration of RO281675 increased insulin secretion, however, only for the L315H mutant. Thus, a glucokinase activator drug therapy may help MODY2 patients not in general, but seems to be a useful strategy for carriers of the L315H glucokinase mutation. - Highlights: • The GK mutants L304P and L315H display a highly reduced enzymatic activity. • In hepatocytes both mutations lower the nuclear/cytoplasmic localization ratio of GK. • Both mutants inhibit stimulus-secretion coupling in insulin-producing cells. • Activation by fructose-2,6-bisphosphatase and by RO281675 is stronger for L315H. • RO281675 stimulates insulin secretion only for the L315H mutant, not for L304P.
ISSN 0006291X
Educational Use Research
Learning Resource Type Article
Publisher Date 2015-09-04
Publisher Place United States
Journal Biochemical and Biophysical Research Communications
Volume Number 464
Issue Number 4


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