L11 - Bacterial exploitation of host cytoskeleton and intracellular trafficking Flashcards
What are the three principal components of the cytoskeleton?
Microtubules, intermediate filaments, and microfilaments.
Which protein is the main constituent of microtubules?
Tubulin.
What is the approximate diameter of microtubules?
About 25 nm.
What are the approximate diameters of intermediate filaments and microfilaments?
Intermediate filaments are ~10 nm and microfilaments (actin) are ~7 nm.
Which Shigella effector modulates the cytoskeleton?
VirA.
Provide an example of an E. coli effector that modulates host cell processes.
EspG (also referenced as orf3).
What types of pathogens are known to produce factors that manipulate the host cell’s cytoskeleton?
Bacteria and Viruses
Why is it significant that multiple bacterial species employ these tactics? Edit- what
It highlights the evolutionary advantage of subverting host cell dynamics for invasion and survival.
What are the two principal mechanisms of bacterial invasion?
The trigger and zipper mechanisms.
How does the “zipper” mechanism facilitate bacterial entry?
By engaging adhesin/receptor interactions that induce localised host cell responses.
What characterises the trigger mechanism of bacterial invasion?
The injection of bacterial proteins into host cells that actively induce cytoskeletal rearrangements.
Which pathogens are typically associated with each trigger and zipper mechanism?
Zipper is linked to Yersinia and Listeria; trigger is linked to Salmonella and Shigella.
Which cellular structure is central to both the trigger and zipper mechanisms?
The actin cytoskeleton.
How do adhesin/receptor interactions contribute to bacterial uptake?
They initiate host cell responses that promote the engulfment of bacteria.
What role do translocated bacterial effectors play in invasion?
They trigger rearrangements in the actin cytoskeleton that aid in internalisation.
What dynamic cellular structure is induced during Salmonella invasion?
Membrane ruffles.
What is the primary cytoskeletal component in membrane ruffles?
Actin.
How can membrane ruffling be visualised experimentally?
Through the use of GFP-tagged actin in cultured epithelial cells such as MDCK cells.
What is the role of membrane ruffles in the process of bacterial invasion?
They remodel the plasma membrane to facilitate bacterial entry.
What role do Rho GTPases play in the cell?
They act as molecular switches that regulate actin cytoskeleton dynamics.
What cellular changes occur when constitutively active Rho GTPases are introduced?
There is stimulation of stress fibres, lamellipodia, or filopodia depending on the specific GTPase involved
Which actin structure is stimulated by active Rho?
Stress fibers.
What does GEF stand for, and what is its role?
Guanine nucleotide exchange factor; it activates GTPases by facilitating the exchange of GDP for GTP.
What is the function of a GAP in the regulation of GTPases?
A GTPase-activating protein (GAP) accelerates the hydrolysis of GTP, inactivating the GTPase.