Naturally occurring mutations of human corticosteroid-binding globulin

Area of Science:

• Biochemistry
• Genetics
• Endocrinology

Background:

• Corticosteroid-binding globulin (CBG) regulates human plasma cortisol levels and bioavailability.
• Proteases can disrupt CBG's steroid-binding properties, leading to altered cortisol regulation.
• Genetic deficiencies affecting CBG levels or function are linked to various clinical conditions.

Purpose of the Study:

• To evaluate 32 uncharacterized nonsynonymous single-nucleotide polymorphisms in SERPINA6 for their impact on CBG production and function.
• To understand how specific genetic variations influence CBG's role in cortisol transport.

Main Methods:

• Production of human CBG mutants in Chinese hamster ovary cells.
• Utilized ELISA, cortisol-binding assays, and Western blotting to assess CBG properties.
• Assessed protease sensitivity of CBG mutants using neutrophil elastase, chymotrypsin, and LasB.

Main Results:

• Identified eight naturally occurring CBG mutants with impaired production or function.
• Observed reduced cortisol-binding affinity in mutants like CBG H14Q, H89Y, I279F, and R260L.
• Detected secretion defects in CBG I48N and P246Q; two mutants showed enhanced protease resistance.

Conclusions:

• Specific amino acid residues significantly impact CBG secretion and function.
• Naturally occurring human CBG mutations warrant consideration in clinical evaluations for diseases involving cortisol level abnormalities.