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Common mechanism unites membrane poration by amyloid and antimicrobial peptides

Nicholas B Last1, Andrew D Miranker

  • 1Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06520-8114, USA.

Proceedings of the National Academy of Sciences of the United States of America
|April 12, 2013
PubMed

Insights

Antimicrobial peptides like magainin 2 and amyloid proteins like islet amyloid polypeptide (IAPP) share a common mechanism for inducing membrane leakage and bacterial cell death through tension-induced pore formation. Their combined activity shows remarkable cross-cooperation, exceeding individual effects significantly.

Area of Science:

  • Biochemistry
  • Molecular Biology
  • Cell Biology

Background:

  • Antimicrobial peptides (AMPs), such as magainin 2, are crucial for innate immunity, mediating bacterial membrane poration.
  • Soluble amyloid proteins, including islet amyloid polypeptide (IAPP), are linked to cell death in amyloidoses via pore formation.
  • Structural and functional similarities suggest a shared mechanism between AMPs and amyloid proteins in membrane disruption.

Purpose of the Study:

  • To investigate and compare the mechanisms of membrane leakage and bacterial cell death induced by magainin 2 and IAPP.
  • To elucidate the role of nucleation-dependent pore formation in these processes.
  • To explore the cooperative interactions between IAPP and magainin 2.

Main Methods:

  • Measurement of liposome leakage kinetics.
  • Bacterial growth inhibition assays.
  • Analysis of peptide-peptide interactions and cooperativity.

Main Results:

  • Both IAPP and magainin 2 induce membrane leakage via nucleation-dependent formation of stable pores.
  • IAPP and magainin 2 exhibit significant cross-cooperativity in inducing leakage and inhibiting bacterial growth, with combined activities over 100-fold greater than individual peptide activities.
  • Cooperativity is independent of direct protein-protein interactions, as demonstrated by D-IAPP's equal cross-cooperativity with magainin 2.

Conclusions:

  • IAPP and magainin 2 utilize a shared mechanism for membrane poration and cytotoxicity.
  • The mechanism involves a cross-cooperative, tension-induced poration process.
  • This shared mechanism highlights a potential common pathway for membrane disruption by diverse peptide systems.

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