Table 2.

Aeromonad effector proteins AexT, AexU, Act, and Hcp mechanisms of action.

Effector	Secretion system	Mechanism of pathogenesis	References
AexT	T3SS	Amino terminal activity targets RhoA and promotes actin depolymerization; carboxy terminal ADP-ribosyltransferase activity.	Braun et al., 2002
AexU	T3SS	Bifunctional-like AexT; activation of caspase-3 and -9 and induction of cell rounding, chromatin condensation; also required for virulence in mice.	Sierra et al., 2007
		GAP-activity (amino terminus) promotes apoptosis and disrupts the cell cytoskeleton as well as NF-κB signaling; prevents signaling of c-Jun, JNK, IκBα, and inhibits IL-6 and IL-8 secretion.	Sierra et al., 2010
		GAP-activity disruption of actin cytoskeleton mediated by down-regulating Rac-1; binding to β4-integrin results in cytotoxicity.	Abolghait et al., 2011
Act 2	T2SS	Induced upregulation of apoptosis-related genes.	Galindo et al., 2003
		Activates MEK1, JNK, ERK1/2, and c-Jun of the MAPK pathway; induces membrane blebbing and increased production of mitochondrial cytochrome C, caspase-3, -8, and -9.	Galindo et al., 2004b
Hcp	T6SS	Caspase 3 activation.	Suarez et al., 2008
		Demonstrates anti-phagocytic properties.	Suarez et al., 2010
		Hcp-2 is part of the T6SS apparatus while Hcp-1 negatively regulates motility and protease production.	Sha et al., 2013

RhoA, Rat sarcoma homolog gene family member A; GAP, GTPase activating protein; NF-κB, nuclear factor Kappa B; JNK, c-Jun N-terminal kinase; IL, interleukin; Rac-1, Rac GTPase activating protein 1; MEK1, MAP/ERK kinase 1; ERK1/2, extracellular signal-regulated kinase 1/2; MAPK, mitogen-activated protein kinases.