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05:51
Coculture Analysis of Extracellular Protein Interactions Affecting Insulin Secretion by Pancreatic Beta Cells
Published on: June 15, 2013
Insulin solubility transitions by pH-dependent interactions with proinsulin C-peptide
Michael Landreh1, Gunvor Alvelius, Hanna Willander
1Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-171 77 Stockholm, Sweden.
The FEBS Journal
|October 31, 2012
Summary
C-peptide influences insulin solubility by coprecipitating with insulin under acidic conditions found in secretory vesicles. This interaction, dependent on glutamate residues, suggests C-peptide modulates insulin structure and secretion.
Area of Science:
- Biochemistry
- Cell Biology
- Endocrinology
Background:
- Proinsulin is processed into insulin and C-peptide in pancreatic β-cells under acidic conditions.
- Mature insulin exhibits reduced solubility and can form amyloid-like structures.
- Insulin is released as distinct phases, with C-peptide's role in secretion unclear.
Purpose of the Study:
- To investigate the interaction between C-peptide and insulin during processing.
- To elucidate C-peptide's role in modulating insulin solubility and secretion.
- To determine the molecular basis of C-peptide's influence on insulin structure.
Main Methods:
- Coprecipitation assays at varying pH and peptide concentrations.
- Analysis of C-peptide's effect on insulin solubility.
- Investigation of conserved glutamate residues in C-peptide's function.
Main Results:
- C-peptide coprecipitates with insulin at the pH of secretory vesicles.
- This precipitation is reversible with pH elevation.
- The interaction is dependent on conserved glutamate residues in C-peptide.
Conclusions:
- C-peptide actively influences insulin solubility.
- Physiological pH changes can alter insulin's quaternary structure and phase transitions.
- C-peptide plays a role in insulin sorting and secretion dynamics.
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