Interaction of membrane vesicles with the Pseudomonas functional amyloid protein FapC facilitates amyloid formation

Zahra Najarzadeh; Hossein Mohammad-Beigi; Jannik Nedergaard Pedersen; Gunna Christiansen; Jan Skov Pedersen; Janni Nielsen; Daniel E Otzen

doi:10.1016/j.bbadva.2022.100055

Interaction of membrane vesicles with the Pseudomonas functional amyloid protein FapC facilitates amyloid formation

BBA Adv. 2022 Sep 19:2:100055. doi: 10.1016/j.bbadva.2022.100055. eCollection 2022.

Authors

Zahra Najarzadeh¹, Hossein Mohammad-Beigi^{1

2}, Jannik Nedergaard Pedersen¹, Gunna Christiansen³, Jan Skov Pedersen^{1

4}, Janni Nielsen¹, Daniel E Otzen¹

Affiliations

¹ Interdisciplinary Nanoscience Centre (iNANO), Aarhus University, Gustav Wieds Vej 14, Aarhus C 8000, Denmark.
² Department of Biotechnology and Biomedicine, Technical University of Denmark, Kgs. Lyngby 2800, Denmark.
³ Faculty of Health Science and Technology, Department of Medical Microbiology and Immunology, Aalborg University, Fredrik Bajers Vej 3b, Aalborg Ø 9220, Denmark.
⁴ Department of Chemistry, Aarhus University, Langelandsgade 140, Aarhus C 8000, Denmark.

Abstract

Functional amyloids (FA) are proteins which are evolutionarily optimized to form highly stable fibrillar structures that strengthen the bacterial biofilm matrix. FA such as CsgA (E. coli) and FapC (Pseudomonas) are secreted to the bacterial surface where they integrate into growing fibril structures projecting from the outer membrane. FA are exposed to membrane surfaces in this process, but it remains unclear how membranes can interact with FA and potentially affect the self-assembly. Here we report the effect of different vesicles (DOPG, DMPG, DOPS, DOPC and DMPC) on the kinetics and structural endpoints of FapC fibrillation using various biophysical techniques. Particularly anionic lipids such as DMPG trigger FapC fibrillation, and the protein's second repeat sequence (R2) appears to be important for this interaction. Vesicles formed from phospholipids extracted from three different Pseudomonas strains (Δfap, ΔFapC and pfap) induce FapC fibrillation by accelerating nucleation. The general aggregation inhibitor epigallocatechin gallate (EGCG) inhibits FapC fibrillation by blocking interactions between FapC and vesicles and redirecting FapC monomers to oligomer structures. Our work indicates that biological membranes can contribute significantly to the fibrillation of functional amyloid.

Keywords: EGCG; FapC protein; ThT kinetics; bacterial amyloid; membrane vesicle.