Secretin self-assembles and interacts spontaneously with phospholipids in vitro

Area of Science:

• Biochemistry
• Biophysics
• Neuroendocrinology

Background:

• Secretin is a 27-amino acid neuropeptide modulating gastrointestinal and neuronal functions.
• It belongs to the secretin/glucagon/vasoactive intestinal polypeptide (VIP) superfamily.
• Secretin is being investigated for autism treatment, but its short circulation half-life is a limitation.

Purpose of the Study:

• To investigate if secretin self-assembles into micelles in aqueous solution.
• To determine if secretin interacts with biomimetic phospholipid membranes.
• To explore if these properties influence secretin's in vivo behavior.

Main Methods:

• Studied secretin's self-assembly in HEPES buffer using critical micelle concentration determination.
• Assessed secretin's interaction with phospholipid membranes by measuring changes in surface pressure.
• Analyzed secretin's conformational changes using spectroscopy in the presence of distearoyl-phosphatidylcholine-poly(ethylene) glycol micelles.

Main Results:

• Secretin self-assembles into micelles in HEPES buffer above 0.4 microM at 25°C.
• Secretin significantly increased phospholipid membrane surface pressure, indicating interaction.
• Secretin transitioned from a random coil to an alpha-helix conformation upon interacting with phospholipid micelles.

Conclusions:

• Secretin exhibits self-assembly and phospholipid-binding properties similar to VIP.
• These biophysical characteristics may enhance secretin's stability and bioactivity in vivo.
• Further research into these properties could optimize secretin-based therapies.