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mBio. 2020 Jan 21;11(1). pii: e02857-19. doi: 10.1128/mBio.02857-19.

Listeria monocytogenes Exploits Host Caveolin for Cell-to-Cell Spreading.

Author information

1
Department of Biological Sciences, Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, British Columbia, Canada.
2
Life Sciences Institute, University of British Columbia, Vancouver, British Columbia, Canada.
3
Department of Cellular and Physiological Sciences, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada.
4
University of Edinburgh Centre for Inflammation Research, Queen's Medical Research Institute, Edinburgh, United Kingdom.
5
MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.
6
Department of Physiology, School of Medicine, Kyung Hee University, Seoul, South Korea.
7
IFOM, Fondazione Istituto FIRC di Oncologia Molecolare, Milan, Italy.
8
Dipartimento di oncologia ed emato-oncologia, Universita' degli Studi di Milano, Milan, Italy.
9
Department of Biological Sciences, Centre for Cell Biology, Development, and Disease, Simon Fraser University, Burnaby, British Columbia, Canada jguttman@sfu.ca.

Abstract

Listeria monocytogenes moves from one cell to another using actin-rich membrane protrusions that propel the bacterium toward neighboring cells. Despite cholesterol being required for this transfer process, the precise host internalization mechanism remains elusive. Here, we show that caveolin endocytosis is key to this event as bacterial cell-to-cell transfer is severely impaired when cells are depleted of caveolin-1. Only a subset of additional caveolar components (cavin-2 and EHD2) are present at sites of bacterial transfer, and although clathrin and the clathrin-associated proteins Eps15 and AP2 are absent from the bacterial invaginations, efficient L. monocytogenes spreading requires the clathrin-interacting protein epsin-1. We also directly demonstrated that isolated L. monocytogenes membrane protrusions can trigger the recruitment of caveolar proteins in a neighboring cell. The engulfment of these bacterial and cytoskeletal structures through a caveolin-based mechanism demonstrates that the classical nanometer-scale theoretical size limit for this internalization pathway is exceeded by these bacterial pathogens.IMPORTANCE Listeria monocytogenes moves from one cell to another as it disseminates within tissues. This bacterial transfer process depends on the host actin cytoskeleton as the bacterium forms motile actin-rich membranous protrusions that propel the bacteria into neighboring cells, thus forming corresponding membrane invaginations. Here, we examine these membrane invaginations and demonstrate that caveolin-1-based endocytosis is crucial for efficient bacterial cell-to-cell spreading. We show that only a subset of caveolin-associated proteins (cavin-2 and EHD2) are involved in this process. Despite the absence of clathrin at the invaginations, the classical clathrin-associated protein epsin-1 is also required for efficient bacterial spreading. Using isolated L. monocytogenes protrusions added onto naive host cells, we demonstrate that actin-based propulsion is dispensable for caveolin-1 endocytosis as the presence of the protrusion/invagination interaction alone triggers caveolin-1 recruitment in the recipient cells. Finally, we provide a model of how this caveolin-1-based internalization event can exceed the theoretical size limit for this endocytic pathway.

KEYWORDS:

Listeria monocytogenes ; actin; actin-based motility; cell-to-cell spreading; endocytosis; epsin-1; invaginations; membrane protrusion

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