Hyperinsulinism-Causing Mutations Cause Multiple Molecular Defects in SUR1 NBD1.

Area of Science:

• Biochemistry
• Molecular Biology
• Genetics

Background:

• The sulfonylurea receptor 1 (SUR1) protein is a key component of pancreatic ATP-sensitive potassium (KATP) channels.
• SUR1 mutations are linked to pancreatic disorders, including neonatal diabetes and congenital hyperinsulinism.
• Congenital hyperinsulinism results from SUR1 mutations that disrupt KATP channel function, leading to excessive insulin secretion.

Purpose of the Study:

• To structurally characterize the first nucleotide binding domain (NBD1) of SUR1.
• To investigate the molecular mechanisms of specific congenital hyperinsulinism-associated SUR1 mutations (G716V, R842G, K890T) within NBD1.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy
• Fluorescence spectroscopy
• Size exclusion chromatography

Main Results:

• The K890T mutation affects multiple regions of NBD1, including MgATP binding sites and coupling helices, reducing MgATP binding affinity.
• G716V and R842G mutations lead to in vitro aggregation of SUR1 NBD1, suggesting domain destabilization.
• These mutations impair the structural integrity and nucleotide-binding capacity of SUR1 NBD1.

Conclusions:

• The study provides structural insights into SUR1 NBD1 and the molecular basis of congenital hyperinsulinism-causing mutations.
• Understanding these structural defects is crucial for developing therapeutic strategies for congenital hyperinsulinism.
• The findings highlight the importance of SUR1 NBD1 structure and function in regulating insulin secretion.