Wnt5A Signaling Mediated Cytoskeletal Actin Modulations Shape the Outcome of Host-Bacteria Interactions

Many human diseases are caused by bacterial infections. Host factors play an important role in determining the persistence vs. eradication of the incumbent bacteria. Among the milieu of host factors involved in immune defense against infections, Wnt5A‐Frizzled5/ROR1 signaling has emerged as an important one based on its established role in bacterial phagocytosis and the maintenance of immune homeostasis. Accordingly, we have deciphered how this signaling pathway differentiates between pathogenic and non‐pathogenic bacteria. Wnt5A signaling results in both uptake and killing of pathogenic bacteria including Pseudomonas sp., Streptococcus sp. and E. coli sp. independent of species specificity through cytoskeletal modulations that involve Rac1/Dvl1 activation. However, some laboratory bacterial strains such as E.coli DH5α and E.coli K12MG1655, that lack pathogenicity islands get internalized but not killed by Wnt5A signaling (Figure 1 ). In comparison to the non‐pathogenic bacterial strains the pathogenic bacterial strains result in decrease of total cellular F‐actin in the host macrophage (Figure 2 ). Revamping of Wnt5A signaling not only aids in recovery of the host cytoskeletal actin but also helps in containment of the infection. As for the non‐pathogenic strains, Wnt5A signaling aided uptake and sustenance of the bacteria inside the host correlate with increased actin polymerization around bacteria containing phagosomes. Interestingly, disruption of Wnt5A dependent actin polymerization in macrophages by actin polymerization inhibitors leads to increased infection by the pathogenic bacteria but killing of the non‐pathogenic lab strains (Figure 2 ). Preliminary observations suggest that the relation of some host commensals with Wnt5A signaling is similar to that of the non‐pathogenic bacteria. Our experimental data suggest that the interplay between Wnt5A induced actin polymerization and the pathogenic potential of incumbent bacteria is a major factor determining the outcome of the host‐bacteria interactions and bacterial persistence vs. eradication. Support or Funding Information This work was supported by funding from DBT, Govt. of India (BT/PR7106/MED/29/639/2012, BT/PR27125/BRB/10/1635/2017) and Institutional funding. SJ and SS were supported by Research Scholar Fellowship from CSIR, Govt. of India. Wnt5A signaling regulates host response to pathogenic and non‐pathogenic bacterial strains. In line with our previous report of Wnt5A signaling mediated killing of Pseudomonas and Streptococcus (Jati et al. Frontiers in immunology, 2018) we observed Wnt5A mediated killing of pathogenic Escherichia coli K1 strain (MOI 10) in both RAW264.7 and peritoneal macrophages (PMϕ) (a,b). But Wnt5A signaling in RAW264.7 and peritoneal macrophages (PMϕ) resulted in enhanced survival of non‐pathogenic bacterial strain Escherichia coli K12MG1655 (MOI 10) (c,d). Data represented as mean ± SEM; * p ≤ 0.05, ** p ≤ 0.005, *** p ≤ 0.0005. PBS: vehicle control for Wnt5A, MOI: Multiplicity of Infection, CFU: Colony Forming Units Figure 1 Alteration of cytoskeletal actin in relation to Wnt5A signaling modulates the outcome of host‐bacteria interaction. Infection with pathogenic Escherichia coli K1 strain results in decrease of total cellular F‐actin compared to the non‐pathogenic Escherichia coli K12MG1655 and Escherichia coli DH5α (a). After 3hrs post infection (T3) of pathogenic Escherichia coli K1 the cellular F‐actin level increased in the Wnt5A treated macrophage set (b) compared to vehicle control (PBS). But in case of non‐pathogenic Escherichia coli DH5α there was no such change (b). In presence of Wnt5A, Arp2 inhibitor CK‐666 (Arp2 inh.) induces clearance of non‐pathogenic Escherichia coli K12MG1655 and Escherichia coli DH5α at 3hrs post infection but inhibits the killing of pathogenic Escherichia coli K1 (c). Data represented as mean ± SEM; * p ≤ 0.05, ** p ≤ 0.005, *** p ≤ 0.0005. MOI: Multiplicity of Infection Figure 2