Localization of host endocytic and actin‐associated proteins during Shigella flexneri intracellular motility and intercellular spreading

Abstract

Shigella flexneri (S. flexneri), the causative agent of bacillary dysentery, uses an effector‐mediated strategy to hijack host cells and cause disease. To propagate and spread within human tissues, S. flexneri bacteria commandeer the host actin cytoskeleton to generate slender actin‐rich comet tails to move intracellularly, and later, plasma membrane actin‐based protrusions to move directly between adjacent host cells. To facilitate intercellular bacterial spreading, large micron‐sized endocytic‐like membrane invaginations form at the periphery of neighboring host cells that come into contact with S. flexneri‐containing membrane protrusions. While S. flexneri comet tails and membrane protrusions consist primarily of host actin cytoskeletal proteins, S. flexneri membrane invaginations remain poorly understood with only clathrin and the clathrin adapter epsin‐1 localized to the structures. Tangentially, we recently reported that Listeria monocytogenes, another actin‐hijacking pathogen, exploits an assortment of caveolar and actin‐bundling proteins at their micron‐sized membrane invaginations formed during their cell‐to‐cell movement. Thus, to further characterize the S. flexneri disease process, we set out to catalog the distribution of a variety of actin‐associated and caveolar proteins during S. flexneri actin‐based motility and cell‐to‐cell spreading. Here we show that actin‐associated proteins found at L. monocytogenes comet tails and membrane protrusions mimic those present at S. flexneri comet tails with the exception of α‐actinins 1 and 4, which were shed from S. flexneri membrane protrusions. We also demonstrate that all known host endocytic components found at L. monocytogenes membrane invaginations are also present at those formed during S. flexneri infections.

Synaptopodin is necessary forShigella flexneriintercellular spread

“…Synaptopodin is described to interact with non-muscle myosin IIb (myosin IIb) and α-actinin-4 at the plasma membrane, where together they form the contractomere complex that generates force so as to enable the extrusion of cells from a monolayer (24). Recent work shows that α-actinin-4 is present at actin structures formed during S. flexneri infection (1). We tested for the recruitment of myosin IIb and α-actinin-4 by immunofluorescence microscopy, and observed both were efficiently recruited to S. flexneri.…”

“…Many cytosolic-dwelling pathogens recruit actin-associated proteins to enable intercellular spread between mammalian cells (1), including Listeria spp ., Rickettsia spp ., Burkholderia spp ., Mycobacterium marinum, Shigella spp ., and poxviruses. The forces generated from the polymerization of actin enable their intracellular motility and movement between cells (2, 3).…”

Chlamydia trachomatis Subverts Alpha-Actinins To Stabilize Its Inclusion

“… Listeria monocytogenes , Salmonella enterica serovar Typhimurium, and Shigella flexneri all form actin-rich structures that regulate invasion, intracellular motility, and cell-cell spread (reviewed in references 29 and 30 ). α-Actinins are also recruited to many of these cytoskeletal structures ( 16 , 17 ), but the precise role of α-actinins in these contexts is unknown. However, recent work has implicated α-actinin 4 in regulating invasion during Escherichia coli and Neisseria meningitidis infections ( 31 , 32 ), suggesting that α-actinin 4 plays an active role in pathogenesis.…”

“…They contribute to diverse cellular processes like cytokinesis, cell adhesion, and motility and, more recently, the regulation of transcriptional activity ( 13 ). While α-actinins are commonly associated with the hijacking of actin by bacterial pathogens ( 16 , 17 ), their role during these infections is poorly understood.…”

From anatomy to immunity in the gastrointestinal system

“…For example, bacteria from the genera Shigella and Salmonella alone account for over 230 million global cases of disease and 650,000 deaths every year (CDC, 2019). Dhanda and Guttman (2022) report original findings on cellular events associated with the intercellular transmission of the enteric pathogen Shigella flexneri . To propagate from cell to cell, Shigella highjack the cellular endocytic machinery and the actin cytoskeletal system and promote the formation of actin‐rich structures that propel the bacteria through the cell cytoplasm and ultimately facilitate their translocation into adjacent cells at points of inter‐cellular membrane contact.…”