RACK1 promotes Shigella flexneri actin-mediated invasion, motility, and cell-to-cell spreading

Karla N Valenzuela-Valderas; Elmira Farrashzadeh; Yuen-Yan Chang; Yunnuo Shi; Renee Raudonis; Brendan M Leung; John R Rohde; Jost Enninga; Zhenyu Cheng

doi:10.1016/j.isci.2023.108216

RACK1 promotes Shigella flexneri actin-mediated invasion, motility, and cell-to-cell spreading

iScience. 2023 Oct 14;26(11):108216. doi: 10.1016/j.isci.2023.108216. eCollection 2023 Nov 17.

Authors

Karla N Valenzuela-Valderas¹, Elmira Farrashzadeh¹, Yuen-Yan Chang², Yunnuo Shi¹, Renee Raudonis¹, Brendan M Leung³, John R Rohde¹, Jost Enninga², Zhenyu Cheng¹

Affiliations

¹ Department of Microbiology and Immunology, Dalhousie University, Halifax, NS B3H 4R2, Canada.
² Unité Dynamique des interactions hôtes-pathogènes, Institut Pasteur and CNRS UMR3691, Université de Paris-Cité, 75724 Paris, France.
³ Department of Applied Oral Sciences, Dalhousie University, Halifax, NS B3H 4R2, Canada.

Abstract

Shigella flexneri is an intracellular bacterium that hijacks the host actin cytoskeleton to invade and disseminate within the colonic epithelium. Shigella's virulence factors induce actin polymerization, leading to bacterial uptake, actin tail formation, actin-mediated motility, and cell-to-cell spreading. Many host factors involved in the Shigella-prompted actin rearrangements remain elusive. Here, we studied the role of a host protein receptor for activated C kinase 1 (RACK1) in actin cytoskeleton dynamics and Shigella infection. We used time-lapse imaging to demonstrate that RACK1 facilitates Shigella-induced actin cytoskeleton remodeling at multiple levels during infection of epithelial cells. Silencing RACK1 expression impaired Shigella-induced rapid polymerizing structures, reducing host cell invasion, bacterial motility, and cell-to-cell spreading. In uninfected cells, RACK1 silencing reduced jasplakinolide-mediated filamentous actin aggregate formation and negatively affected actin turnover in fast polymerizing structures, such as membrane ruffles. Our findings provide a role of RACK1 in actin cytoskeleton dynamics and Shigella infection.

Keywords: Bacteriology; Cellular physiology; Functional aspects of cell biology.