Table 1B.

Characterised CT T3SS effector proteins and their functions in chlamydial pathogenesis.

Effector Protein	Family Conserved?	Localisation	Host Target/s	Function	References
IncV (CT005)	Specific to C. trachomatis	Inclusion membrane	VAPA/B	Tethers the inclusion to the endoplasmic reticulum’s membrane contact sites.	(Stanhope et al., 2017; Stanhope and Derré, 2018; Andersen et al., 2021)
GlgX (CT042)	Specific to C. trachomatis	Inclusion lumen	Unknown	Debranches host glycogen.	(Gehre et al., 2016; LaBrie et al., 2019)
Pls1 (CT049)*	Specific to C. trachomatis	Inclusion lumen and membrane	Unknown	Proposed to mediate expansion of the inclusion.	(Jorgensen and Valdivia, 2008)
MrcA (CT101)	Specific to C. trachomatis	Inclusion membrane	Inositol 1,4,5-triphosphate receptor 3 (ITPR3)	Regulates CT’s release by mediating the myosin phosphatase pathway.	(Nguyen et al., 2018; Sah and Lutter, 2020)
CteG (CT105)	Specific to C. trachomatis, C. muridarum, and C. suis	Golgi complex and plasma membrane of host eukaryotic cell	Unknown	Implicated in eukaryotic cell’s vesicle trafficking and centrosome amplification.	(Pais et al., 2019; Steiert et al., 2023)
IncA (CT119)	Specific to C. trachomatis	Inclusion membrane	Vamp 3/7/8	Increases growth rate and production of EBs during replication through homotypic inclusion fusion.	(Suchland et al., 2000; Dehoux et al., 2011; Mueller et al., 2014; da Cunha et al., 2017; Cingolani et al., 2019)
IPAM (CT223)	Specific to C. trachomatis	Inclusion membrane	Centrosomal protein 170 (CEP170)	Maintains cytoskeletal stabilisation for vesicular trafficking.	(Dumoux et al., 2015; Olson-Wood et al., 2021)
CpoS (CT229)	Specific to C. trachomatis, C. caviae, and C. muridarum	Inclusion membrane	Myosin phosphatase	Regulates host vesicle trafficking across the plasma membrane and promotes inclusion growth.	(Rzomp et al., 2006; Andersen et al., 2021)
TarP (CT456)	Yes	Eukaryotic cell cytosol	Actin**, FAK, Vinculin, Rac guanine exchange factors (Sos1, Vav2)	Facilitates invasion of host epithelia.	(Clifton et al., 2004; Clifton et al., 2005; Lane et al., 2008; Mueller et al., 2014; Thwaites et al., 2015; Faris et al., 2020; Pedrosa et al., 2020)
TmeA (CT694)	Specific to C. trachomatis and C. muridarum	Inclusion membrane and eukaryotic cell plasma membrane	N-WASP GTPase, Ahnak	Facilitates invasion of host epithelia.	(Bullock et al., 2012; Mueller et al., 2014; McKuen et al., 2017; Faris et al., 2020)
TmeB (CT695)	Specific to C. trachomatis	Inclusion and eukaryotic cell plasma membrane	Unknown	Implicated function in assisting pathogen uptake into host cell.	(Mueller and Fields, 2015; McKuen et al., 2017; Andersen et al., 2021; Scanlon et al., 2023)
Nue (CT737)	Specific to C. trachomatis	Eukaryotic cell nucleus	H2B, H3 and H4	Targets and translocates the host cell nucleus.	(Pennini et al., 2010; Andersen et al., 2021)
InaC (CT813)	Specific to C. trachomatis and C. muridarum	Inclusion membrane	14-3-3 proteins, ARF1, ARF4, Vamp7 and Vamp8	Regulates inclusion structure and stability and nutrient acquisition.	(Wesolowski et al., 2017; Andersen et al., 2021; Olson-Wood et al., 2021)
CT850	Yes	Inclusion membrane	DYNLT1	Promote inclusion tethering to host cell nucleus.	(Mital et al., 2015)
TepP (CT875)	Specific to C. trachomatis	Eukaryotic cell cytosol near the inclusion	CRK, CRKL, GSK3B, PI3K	Prevents neutrophil-mediated recruitment of immune cells and permits prolonged infections.	(Yi-Shan et al., 2014; Andersen et al., 2021; Dolat and Valdivia, 2021)
CopN (Chlamydial outer protein N) (CT089)	Specific to C. trachomatis and C. pneumoniae	Inclusion membrane	αβ-tubulin	Regulates T3SS effectors secretion and translocation proteins.	(Archuleta et al., 2011; Hanson et al., 2015)

*Currently considered to be a CT T3SS substrate but yet to be experimentally validated.

**TarP direct polymerisation of actin has not been directly associated to plasma membrane reorganisation during EB invasion.