Control of insulin receptor affinity by a Ca2+-sensitive binding site

Area of Science:

• Biochemistry
• Molecular Biology
• Endocrinology

Background:

• Insulin resistance is a key factor in metabolic disorders.
• Understanding insulin receptor regulation is crucial for metabolic health.

Purpose of the Study:

• To investigate the role of calcium ions (Ca2+) in modulating insulin receptor binding.
• To elucidate the mechanism by which Ca2+ affects insulin receptor affinity and kinetics.

Main Methods:

• Utilized membrane and solubilized receptor preparations.
• Assessed [125I]insulin binding kinetics and receptor number.
• Tested effects of various divalent cations (Ca2+, Ba2+, Mg2+, Sr2+) and chelators (EDTA).

Main Results:

• Calcium (Ca2+) significantly increased insulin receptor binding affinity and the initial rate of insulin association.
• Ca2+ did not alter the total number of insulin receptors.
• Divalent cations with similar ionic properties mimicked Ca2+'s effect on affinity.
• EDTA and oleic acid reduced binding and affinity, effects reversible by Ca2+.

Conclusions:

• Calcium ions (Ca2+) play a regulatory role in insulin receptor function.
• Ca2+ binding to the receptor or associated sites induces conformational changes, enhancing affinity.
• These findings suggest a potential therapeutic target for modulating insulin sensitivity.