The ubiquitin C-terminal hydrolase UCH-L1 promotes bacterial invasion by altering the dynamics of the actin cytoskeleton

Abstract

SummaryInvasion of eukaryotic target cells by pathogenic bacteria requires extensive remodelling of the membrane and actin cytoskeleton. Here we show that the remodelling process is regulated by the ubiquitin C-terminal hydrolase UCH-L1 that promotes the invasion of epithelial cells by Listeria monocytogenes and Salmonella enterica. Knockdown of UCH-L1 reduced the uptake of both bacteria, while expression of the catalytically active enzyme promoted efficient internalization in the UCH-L1-negative HeLa cell line. The entry of L. monocytogenes involves binding to the receptor tyrosine kinase Met, which leads to receptor phosphorylation and ubiquitination. UCH-L1 controls the early membrane-associated events of this triggering cascade since knockdown was associated with altered phosphorylation of the c-cbl docking site on Tyr1003, reduced ubiquitination of the receptor and altered activation of downstream ERK1/2-and AKT-dependent signalling in response to the natural ligand Hepatocyte Growth Factor (HGF). The regulation of cytoskeleton dynamics was further confirmed by the induction of actin stress fibres in HeLa expressing the active enzyme but not the catalytic mutant UCH-L1 C90S. These findings highlight a previously unrecognized involvement of the ubiquitin cycle in bacterial entry. UCH-L1 is highly expressed in malignant cells that may therefore be particularly susceptible to invasion by bacteria-based drug delivery systems.

KSHV LANA and EBV LMP1 induce the expression of UCH-L1 following viral transformation

“…Recent studies demonstrate that inhibition of the expression of UCH-L1 reduces the tumorigenic phenotype of transformed cells, including virus-transformed B-lymphocytes (Bheda et al, 2009a; Kim et al, 2008; Rolen et al, 2008). UCH-L1 also associates with cytoskeletal components, including microtubules (Bheda et al, 2010; Kabuta et al, 2008) and actin filaments (Basseres et al, 2010), and it physically associates with mitotic spindles (Bheda et al, 2010), which suggests a potential role in the regulation of mitosis. Furthermore, oncogenic transcription factors, such as B-Myb and β-catenin/TCF, up-regulate the expression of the uch-l1 gene (Bheda et al, 2009b; Long et al, 2003).…”

Impact ofSalmonella entericaType III Secretion System Effectors on the Eukaryotic Host Cell

“…It has been suggested that interactions of IQGAP1 with Salmonella-activated Rac1 and Cdc42 maintain them in their active form [32,33]. Another host factor that contributes to bacterial invasion by altering the dynamics of the actin cytoskeleton is the ubiquitin C-terminal hydrolase UCH-L1 [34]. Since SopA, SopB, and SopE are substrates of the ubiquitin proteasome system, it has been suggested that UCH-L1, acting as a deubiquitinating enzyme, could play a role in controlling the half-life of these effectors and/or the activity of small GTPases of the Rho subfamily.…”

Deubiquitinating Enzymes as Promising Drug Targets for Infectious Diseases

“…Particularly, UCHL3 has been found to be significantly downregulated during infection with virulent strain, as compared to control cells, or cells infected with virulence plasmid-cured strain. A close homologue of this DUB, UCHL1, has been already shown to be involved in bacterial entry of Listeria monocytogenes and Salmonella enterica Typhimurium [80], therefore our current finding might be physiologically very interesting and warrants further study.…”

“…A human ubiquitin C-terminal hydrolase UCHL1 has been shown to promote Listeria monocytogenes and Salmonella enterica epithelial cell invasion and induce spontaneous formation of actin stress fibers, regulating early events in receptor signaling [80]. In particular, UCHL1 controls early membrane-associated pathways related to the L. monocytogenes entry into the host cell, such as activation of downstream ERK1/2- and AKT-dependent signaling in response to the Hepatocyte Growth Factor (HGF).…”