Structural studies of a neuropeptide precursor protein with an RGD proteolytic site

Area of Science:

• Biochemistry
• Molecular Biology
• Neuroscience

Background:

• The snail Lymnaea stagnalis synthesizes a neuropeptide precursor with multiple Arg-Gly-Asp (RGD) motifs.
• Prohormone convertases (PCs) cleave these RGD sites to generate mature neuropeptides.
• The role of RGD site conformation and flanking residues in processing and biological activity is not fully understood.

Purpose of the Study:

• To investigate the structural and functional consequences of RGD site variations in the L. stagnalis neuropeptide precursor.
• To determine how peptide conformation and flanking residues affect RGD activity and prohormone processing by PC2 and furin.

Main Methods:

• Nuclear Magnetic Resonance (NMR) spectroscopy to determine peptide conformations.
• Platelet aggregation assays to assess RGD activity.
• In vitro processing assays using recombinant prohormone convertases (PC2 and furin).

Main Results:

• A native peptide with proline after the RGD site showed minimal RGD region structure, no platelet aggregation inhibition, and was processed by PC2 and furin.
• A variant peptide with serine after the RGD site adopted a reverse turn conformation, potently inhibited platelet aggregation, and was processed similarly.
• Significant conformational differences were observed between the native and variant peptides.

Conclusions:

• Peptide flexibility around the RGD site, influenced by flanking residues like proline, plays a crucial role in biological activity (e.g., platelet aggregation).
• The flexibility of the RGD site, rather than its precise conformation, may be a key determinant for efficient processing by prohormone convertases.
• These findings provide a molecular basis for understanding how precursor processing is regulated and how RGD motifs contribute to biological functions.