Table 2.
List of T3SS effector proteins that have been implicated in SCV biogenesis.
| Effector | Intracellular localization | Enzymatic activity | Host target | Function with respect to SCV | References | |
|---|---|---|---|---|---|---|
| Translocated by Salmonella | Ectopically expressed | |||||
| SipA/SspA (T3SS1) | “Foci” in the vicinity of bacteria at early times (≤ 30 min p.i.), SCV at later times (≤ 8 h p.i.) | Cortical actin | Actin | SCV positioning | [27,58–60] | |
| SopA (T3SS1) | Mitochondria | Mitochondria | E3 ubiquitin ligase | HsRMA1 | SCV integrity | [25,61,62] |
| SopB/SigD (T3SS1) | SCV | Membranes of swollen vesicles, lamellipodia | Inositol polyphosphate phosphatase | Membrane phospholipids | Promotes membrane fission during invasion, PI(3)P production in and VAMP8 recruitment to ruffles, Lamp acquisition to SCV | [28,29,32,33,63–65] |
| SopD (T3SS1/T3SS2) | Cytosol | Cytosol and vesicles | Membrane fission and macropinosome formation during invasion | [35,36,66] | ||
| PipB (T3SS2) | SCV, Sifs | [67] | ||||
| PipB2 (T3SS2) | SCV, Sifs | Vesicles at cell periphery | Kinesin-1 | Anterograde movement of Sifs and late endosomes/lysosomes | [19,48,49] | |
| SifA (T3SS2) | SCV, Sifs | Lamp-enriched tubules and vesicles, plasma membrane, cytosol, nucleus | SKIP, Rab7 | SCV positioning, membrane integrity and dynamics, Sif formation | [45,47,68–73] | |
| SifB (T3SS2) | SCV, Sifs | Cytosol | [73] | |||
| SopD2 (T3SS2) | SCV, Sifs | Lamp-rich vesicles and tubules | Sif formation | [35,66] | ||
| SpiC/SsaB (T3SS2) | Conflicting data | Cytosol and nucleus | Hook 3, TassC | Inhibition of vesicle fusion with SCV, VAP formation, Sif formation | [37–39,74–77] | |
| SseF (T3SS2) | SCV, Sifs | Microtubule bundles, Golgi network | SCV positioning and motility, Sif formation, microtubule bundling | [43–45,77–79] | ||
| SseG (T3SS2) | SCV, Sifs | Golgi network, perinuclear aggregates, microtubule bundles | SCV positioning, and motility, Sif formation, microtubule bundling | [11,43–45,77–79] | ||
| SseI/SrfH | VAP | Membrane ruffles and focal adhesions | Filamin, TRIP6 | Actin rearrangements | [55,80,81] | |
| SseJ/SifC (T3SS2) | SCV, Sifs | “Globular membranous compartments” | Deacylase | SCV membrane dynamics, negative regulation of Sifs | [50,51,73] | |
| SspH2 (T3SS2) | VAP | Sites of actin polymerization, membrane ruffles and perinuclear region | Inhibits actin polymerization in vitro | Filamin, profilin | [55] | |
| SteC (STM1698) (T3SS2) | SCV, Sifs, VAP | Cytosolic | Kinase | Actin cytoskeleton | Required for VAP | [54] |
SKIP, SifA and kinesin-interacting protein; VAP, vacuole-associated actin polymerization.