EnterohemorrhagicEscherichia coli(EHEC) and enteropathogenic Escheri-chia coli (EPEC) are attaching⁄effacing pathogens that possess a type III
secretion system and deliver a variety of effectors into host cells for suc-cessful infection. EHEC produces at least 20 effector families with various
Enterohemorrhagic and enteropathogenicEscherichia coliproduce various
effector proteins that are directly injected into the host-cell cytosol through
the type III secretion system. E. colisecreted protein (Esp)B is one such
effector protein, and affects host-cell morphology by reorganizing actin net-works.
A variety of microbes manipulate the cytoskeleton of mammalian cells to
promote their internalization, motility and⁄or spread. Among such bacte-ria, enteropathogenic Escherichia coliand enterohemorrhagic Escherichia
coliare closely related pathogens that adhere to human intestinal cells and
reorganize the underlying actin cytoskeleton into ‘pedestals’.
Heterotrimeric G proteins participate in signal transduction by transferring
signals from cell surface receptors to intracellular effector molecules.
G proteins also interact with microtubules and participate in microtubule-dependent centrosome⁄chromosome movement during cell division, as well
as neuronal differentiation.
The ATP-hydrolysing enzymes (Na
- and Ca
integral membrane proteins that play important roles in the exchange of
ions and nutrients between the exterior and interior of cells, and are
involved in signal transduction pathways. Activity of these ATPases is reg-ulated by several specific effectors.
Various bacterial protein toxins and effectors target the actin cytoskeleton.
At least three groups of toxins⁄effectors can be identified, which directly
modify actin molecules. One group of toxins⁄effectors causes ADP-ribosy-lation of actin at arginine-177, thereby inhibiting actin polymerization.