Bacterial effector kinases and strategies to identify their target host substrates

Abstract

Post-translational modifications (PTMs) are critical in regulating protein function by altering chemical characteristics of proteins. Phosphorylation is an integral PTM, catalyzed by kinases and reversibly removed by phosphatases, that modulates many cellular processes in response to stimuli in all living organisms. Consequently, bacterial pathogens have evolved to secrete effectors capable of manipulating host phosphorylation pathways as a common infection strategy. Given the importance of protein phosphorylation in infection, recent advances in sequence and structural homology search have significantly expanded the discovery of a multitude of bacterial effectors with kinase activity in pathogenic bacteria. Although challenges exist due to complexity of phosphorylation networks in host cells and transient interactions between kinases and substrates, approaches are continuously being developed and applied to identify bacterial effector kinases and their host substrates. In this review, we illustrate the importance of exploiting phosphorylation in host cells by bacterial pathogens via the action of effector kinases and how these effector kinases contribute to virulence through the manipulation of diverse host signaling pathways. We also highlight recent developments in the identification of bacterial effector kinases and a variety of techniques to characterize kinase-substrate interactions in host cells. Identification of host substrates provides new insights for regulation of host signaling during microbial infection and may serve as foundation for developing interventions to treat infection by blocking the activity of secreted effector kinases.

CPK1‐HSP90 phosphorylation and effector XopC2–HSP90 interaction underpin the antagonism during cassava defense‐pathogen infection

“…XopC2 hijacks MeHSP90.9 to inhibit its phosphorylation by MeCPK1 and transcriptional activation of downstream genes Considering that MeHSP90.9 acts as a positive regulator against Xam (Wei et al, 2021a,b), we speculated whether MeHSP90.9 targets Xam proteins during cassava-Xam interaction. To elucidate this possibility, Y2H assay screening and further DNAsequencing identified effector XopC2, a non-TAL type III effector (Qin et al, 2018;St Louis et al, 2023), as a MeHSP90.9 candidate interacting protein. This protein interaction was further verified in vivo and in vitro using Y2H, BiFC and pull-down assays (Fig.…”