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Mutagenesis and Functional Analysis of Ion Channels Heterologously Expressed in Mammalian Cells
Published on: October 1, 2010
[The functional analysis of glucokinase gene E339K mutation].
Yun-feng Shen1, Hua Liang, Meng-yin Cai
1Department of Endocrinology, the Third Affiliated Hospital, Sun Yat-sen University, Diabetes Research Centre of Guangdong Province, Guangzhou 510630, China.
Zhonghua Nei Ke Za Zhi
|October 29, 2010
Summary
The glucokinase (GCK) E339K mutation causes maturity-onset diabetes of the young-2 (MODY2) by reducing protein yield and stability, and altering enzyme kinetics. This impacts glucose regulation, leading to higher blood glucose levels.
Area of Science:
- Biochemistry
- Molecular Biology
- Genetics
Background:
- Maturity-onset diabetes of the young-2 (MODY2) is a genetic form of diabetes caused by mutations in the glucokinase (GCK) gene.
- Understanding the molecular mechanisms of specific GCK mutations is crucial for diagnosing and managing MODY2.
Purpose of the Study:
- To investigate the molecular mechanisms by which the glucokinase (GCK) E339K mutation leads to maturity-onset diabetes of the young-2 (MODY2).
Main Methods:
- Assessed clinical parameters including fasting plasma glucose (FPG), 2-hour oral glucose tolerance test glucose (2hPG), HbA1c, and fasting insulin (FIns).
- Constructed and expressed mutant GCK protein using site-directed mutagenesis and affinity chromatography.
- Evaluated enzymatic kinetics and thermal stability of wild-type and mutant GCK proteins.
Main Results:
- The E339K mutation resulted in significantly higher FPG, 2hPG, and HbA1c levels, alongside lower FIns and HOMA-β, compared to non-mutants.
- Mutant GCK exhibited reduced protein yield, decreased affinity for glucose and ATP, and diminished catalytic activity (lower Kcat).
- Protein thermal instability was also observed in the mutant GCK.
Conclusions:
- The GCK E339K mutation contributes to MODY2 development by impairing protein yield and stability.
- Alterations in enzymatic kinetics, including reduced glucose and ATP affinity and catalytic efficiency, further explain the pathogenic mechanism of this MODY2-associated mutation.
