TY - JOUR

T1 - Membrane invagination induced by Shiga toxin B-subunit

T2 - from molecular structure to tube formation

AU - Pezeshkian, W.

AU - Hansen, A. G.

AU - Johannes, L.

AU - Khandelia, H.

AU - Shillcock, J. C.

AU - Kumar, P. B. S.

AU - Ipsen, J. H.

PY - 2016

Y1 - 2016

N2 - The bacterial Shiga toxin is composed of an enzymatically active A-subunit, and a receptor-binding homopentameric B-subunit (STxB) that mediates intracellular toxin trafficking. Upon STxB-mediated binding to the glycolipid globotriaosylceramide (Gb(3)) at the plasma membrane of target cells, Shiga toxin is internalized by clathrin-dependent and independent endocytosis. The formation of tubular membrane invaginations is an essential step in the clathrin-independent STxB uptake process. However, the mechanism by which STxB induces these invaginations has remained unclear. Using a combination of all-atom molecular dynamics and Monte Carlo simulations we show that the molecular architecture of STxB enables the following sequence of events: the Gb(3) binding sites on STxB are arranged such that tight avidity-based binding results in a small increment of local curvature. Membrane-mediated clustering of several toxin molecules then creates a tubular membrane invagination that drives toxin entry into the cell. This mechanism requires: (1) a precise molecular architecture of the STxB binding sites; (2) a fluid bilayer in order for the tubular invagination to form. Although, STxB binding to the membrane requires specific interactions with Gb(3) lipids, our study points to a generic molecular design principle for clathrin-independent endocytosis of nanoparticles.

AB - The bacterial Shiga toxin is composed of an enzymatically active A-subunit, and a receptor-binding homopentameric B-subunit (STxB) that mediates intracellular toxin trafficking. Upon STxB-mediated binding to the glycolipid globotriaosylceramide (Gb(3)) at the plasma membrane of target cells, Shiga toxin is internalized by clathrin-dependent and independent endocytosis. The formation of tubular membrane invaginations is an essential step in the clathrin-independent STxB uptake process. However, the mechanism by which STxB induces these invaginations has remained unclear. Using a combination of all-atom molecular dynamics and Monte Carlo simulations we show that the molecular architecture of STxB enables the following sequence of events: the Gb(3) binding sites on STxB are arranged such that tight avidity-based binding results in a small increment of local curvature. Membrane-mediated clustering of several toxin molecules then creates a tubular membrane invagination that drives toxin entry into the cell. This mechanism requires: (1) a precise molecular architecture of the STxB binding sites; (2) a fluid bilayer in order for the tubular invagination to form. Although, STxB binding to the membrane requires specific interactions with Gb(3) lipids, our study points to a generic molecular design principle for clathrin-independent endocytosis of nanoparticles.

KW - FORCE-FIELD

KW - DYNAMICS

KW - CURVATURE

KW - GROMACS

KW - SCISSION

KW - SITES

KW - ENTRY

U2 - 10.1039/c6sm00464d

DO - 10.1039/c6sm00464d

M3 - Journal article

VL - 12

SP - 5164

EP - 5171

JO - Soft Matter

JF - Soft Matter

SN - 1744-683X

IS - 23

ER -