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Pathogenic Yersinia bacteria cause a range of human diseases. To modulate and evade host immune systems, these yersiniae inject effector proteins into host macrophages. One such protein, the serine/threonine kinase YopO (YpkA in Yersinia pestis), uses monomeric actin as bait to recruit and phosphorylate host actin polymerization-regulating proteins, including the actin-severing protein gelsolin, to disrupt actin filaments and thus impair phagocytosis. However, the YopO phosphorylation sites on gelsolin and the consequences of YopO-mediated phosphorylation on actin remodeling have yet to be established. Here we determined the effects of YopO-mediated phosphorylation on gelsolin and identified its phosphorylation sites by mass spectrometry. YopO phosphorylated gelsolin in the linker region between gelsolin homology domains G3 and G4, which, in the absence of calcium, are compacted but adopt an open conformation in the presence of calcium, enabling actin binding and severing. Using phosphomimetic and phosphodeletion gelsolin mutants, we found that YopO-mediated phosphorylation partially mimics calcium-dependent activation of gelsolin, potentially contributing to a reduction in filamentous actin and altered actin dynamics in phagocytic cells. In summary, this work represents the first report of the functional outcome of serine/threonine phosphorylation in gelsolin regulation and provides critical insight into how YopO disrupts normal gelsolin function to alter host actin dynamics and thus cripple phagocytosis.

Original publication

DOI

10.1074/jbc.M116.757971

Type

Journal article

Journal

J Biol Chem

Publication Date

12/05/2017

Volume

292

Pages

8092 - 8100

Keywords

Yersinia, actin, gelsolin, infectious disease, kinase, mass spectrometry (MS), phagocytosis, phosphorylation, Actin Cytoskeleton, Actins, Bacterial Proteins, Binding Sites, Calcium, Gelsolin, Humans, Macrophages, Mass Spectrometry, Molecular Dynamics Simulation, Mutation, Phagocytosis, Phosphorylation, Protein Domains, Protein-Serine-Threonine Kinases, Pyrenes, Serine, Threonine, Yersinia