Endogenous pore-forming protein complex targets acidic glycosphingolipids in lipid rafts to initiate endolysosome regulation

Xiao-Long Guo,Yun Zhang,Wen-Hui Lee,Sheng-An Li,Jin-Yang Liang,Ling-Zhen Liu,Yang Xiang,Qi-Quan Wang

doi:10.1038/s42003-019-0304-y

Abstract

Bacterial pore-forming toxin aerolysin-like proteins (ALPs) are widely distributed in animals and plants. However, functional studies on these ALPs remain in their infancy. βγ-CAT is the first example of a secreted pore-forming protein that functions to modulate the endolysosome pathway via endocytosis and pore formation on endolysosomes. However, the specific cell surface molecules mediating the action of βγ-CAT remain elusive. Here, the actions of βγ-CAT were largely attenuated by either addition or elimination of acidic glycosphingolipids (AGSLs). Further study revealed that the ALP and trefoil factor (TFF) subunits of βγ-CAT bind to gangliosides and sulfatides, respectively. Additionally, disruption of lipid rafts largely impaired the actions of βγ-CAT. Finally, the ability of βγ-CAT to clear pathogens was attenuated in AGSL-eliminated frogs. These findings revealed a previously unknown double binding pattern of an animal-secreted ALP in complex with TFF that initiates ALP-induced endolysosomal pathway regulation, ultimately leading to effective antimicrobial responses.

Highlights

Bacterial pore-forming toxin aerolysin-like proteins (ALPs) are widely distributed in animals and plants
Results βγ-CAT functions are inhibited by acidic glycosphingolipids (AGSLs). βγ-CAT exerts its immunoregulatory activity by triggering inflammasome activation to induce IL-1β release, as we previously demonstrated[15]
Sulfatides are another predominant type of sulfate substituent containing AGSLs in the cell membranes of vertebrates and are primarily found at the plasma membrane outer leaflet of most eukaryotic cells[22]

Summary

Introduction

Bacterial pore-forming toxin aerolysin-like proteins (ALPs) are widely distributed in animals and plants. The ability of βγ-CAT to clear pathogens was attenuated in AGSL-eliminated frogs These findings revealed a previously unknown double binding pattern of an animal-secreted ALP in complex with TFF that initiates ALP-induced endolysosomal pathway regulation, leading to effective antimicrobial responses. After undergoing an extensive conformational change under specific conditions, these nonclassical membrane proteins can form transmembrane pores of various sizes (2 to 50 nm), which function as channels for passing different molecules, including ions, proteins, peptides and nucleic acids[3,4,5] In addition to their well-known functions in cell death[6,7], emerging evidence suggests that pore-forming proteins play pivotal pathophysiological roles in living organisms, functioning in processes such as cell differentiation, reproduction and tissue repair[3,8,9,10], but the related mechanisms remain unclear. These findings revealed a double-receptor binding model of a vertebrate ALP and TFF complex, suggesting a pattern underlying the target selectivity of animal ALPs

Methods

Results

Conclusion