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Updated: May 9, 2026
11:10
High-throughput Assay to Phenotype Salmonella enterica Typhimurium Association, Invasion, and Replication in Macrophages
Published on: August 11, 2014
Formin-mediated actin polymerization promotes Salmonella invasion
Dorothy Truong1, Danielle Brabant, Mikhail Bashkurov
1Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada, M5G 1X8; Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada, M5S 1A8.
Cellular Microbiology
|July 23, 2013
Summary
Salmonella invasion relies on FHOD1, a formin protein, and its phosphorylation by ROCK II. This pathway controls actin polymerization and membrane protrusion for bacterial uptake.
Area of Science:
- Cellular microbiology
- Host-pathogen interactions
- Actin dynamics
Background:
- Salmonella Typhimurium utilizes Type 3 secretion system (T3SS) effectors to manipulate host cell actin cytoskeleton, facilitating bacterial entry.
- While the Arp2/3 complex is implicated in Salmonella invasion, its non-essential role suggests involvement of other actin regulators.
Purpose of the Study:
- To investigate the role of formin homology 2 domain containing 1 (FHOD1) in Salmonella host cell invasion.
- To elucidate the molecular mechanisms by which FHOD1 contributes to bacterial uptake.
Main Methods:
- Immunofluorescence microscopy to visualize FHOD1 and Arp2/3 localization at the invasion site.
- Western blotting to detect FHOD1 phosphorylation during infection.
- Kinase assays and genetic manipulation to assess the roles of ROCK I and ROCK II.
Main Results:
- FHOD1 and Arp2/3 complex localize to distinct microdomains at the Salmonella invasion site, regulating separate aspects of membrane protrusion.
- FHOD1 phosphorylation is crucial for promoting bacterial internalization and is dependent on ROCK II recruitment to the invasion site.
- ROCK II, but not ROCK I, is essential for FHOD1 phosphorylation and subsequent Salmonella invasion.
Conclusions:
- FHOD1 acts as a novel regulator of Salmonella invasion, distinct from the Arp2/3 complex.
- A phospho-dependent pathway involving ROCK II and FHOD1 drives actin polymerization necessary for Salmonella entry.
- These findings reveal a critical role for FHOD1 in host-pathogen interactions and actin-based bacterial invasion.
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Their main function is to guide migrating cells during normal tissue morphogenesis or cancer metastasis by recognizing and making initial contacts with the extracellular matrix. However, they can also act as stationary cell anchors or help to establish communication...
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01:13Actin Polymerization and Cell Motility
Actin is a family of globular proteins that are highly abundant in eukaryotic cells. It makes up approximately 1-5% of total cell protein concentration. Actin monomers polymerize to form a complex network of polarized filaments, the actin cytoskeleton, that plays a crucial role in many cellular processes, including cell motility, division, endocytosis, and metastasis of cancer cells.
Actin cytoskeleton dynamics can produce pushing, pulling, and resistance forces that help the cell to migrate.
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01:42Actin Polymerization
Actin polymerization occurs through the head-to-tail association of binding sites on monomeric actin or G-actin to form filamentous or F-actin. The polymerization can be divided into three phases ̶ nucleation, elongation, and steady-state phase.
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The polymerization of G-actin monomers into filamentous F-actin is a multi-step process. Once the F-actins are formed, they can bundle together in different arrangements to form higher-order networks and regulate cellular functions. Common examples include the formation of lamellipodia and filopodia at the cell's leading edge by actin reorganization in a migrating cell. The microvilli on the brush border epithelial cells are also formed through the F-actin network.
The high-order actin networks...
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01:14Generation of Straight or Branched Actin Filaments
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Arp2/3 Complex
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