Sequestering of Rac by the Yersinia Effector YopO Blocks Fcγ Receptor-mediated Phagocytosis

Abstract

Pathogenic Yersinia species neutralize innate immune mechanisms by injecting type three secretion effectors into immune cells, altering cell signaling. Our study elucidates how one of these effectors, YopO, blocks phagocytosis. We demonstrate using different phagocytic models that YopO specifically blocks Rac-dependent Fc␥ receptor internalization pathway but not complement receptor 3-dependent uptake, which is controlled by Rho activity. We show that YopO prevents Rac activation but does not affect Rac accumulation at the phagocytic cup. In addition, we show that plasma membrane localization and the guanine-nucleotide dissociation inhibitor (GDI)-like domain of YopO cooperate for maximal anti-phagocytosis. Although YopO has the same affinity for Rac1, Rac2, and RhoA in vitro, it selectively interacts with Rac isoforms in cells. This is due to the differential localization of the Rho family G proteins in resting cells; Rac isoforms partially exist as a GDI-free pool at the membrane of resting cells, whereas RhoA is trapped in the cytosol by RhoGDI␣. We propose that YopO exploits this basic difference in localization and availability to selectively inhibit Rac-dependent phagocytosis.

Regulation of Yersinia Protein Kinase A (YpkA) Kinase Activity by Multisite Autophosphorylation and Identification of an N-terminal Substrate-binding Domain in YpkA

“…Upon translocation into the host cell, the N terminus of YpkA localizes the protein to the inner surface of the host cell plasma membrane, where it is in close proximity to key proteins involved in transducing extracellular signals into eukaryotic cells. Groves et al demonstrated the importance of YpkA subcellular localization to the plasma membrane for RhoGTPase binding (33). YpkA was shown to selectively inhibit Rac-dependent Fc␥ receptor-mediated phagocytosis by specifically targeting endogenous membranebound Rac isoforms in cells (33).…”

“…A region within the C-terminal domain (residues 431-612, RhoGDI) of YpkA possesses Rho GTPase binding guanine nucleotide dissociation inhibitor (GDI)-like activity and has been shown to be important for inactivation of the small Rho GTPases, RhoA and Rac1 (32). The GDI-like activity interferes with phagocytosis by disrupting the host actin cytoskeleton (33). Substitution of three amino acids (Y591A, N595A, E599A) in the GDI-like domain interferes with Rho GTPase binding (32).…”

Differential Protein Expression in EC304 Gastric Cancer Cells Induced by Alphastatin

“…In 2004, Carolyn et al found that alphastatin could inhibit angiogenesis in vitro, and could inhibit tumour angiogenesis in mice (Groves et al, 2010). Experiments revealed that alphastatin could inhibit angiogenesis by vascular endothelial cells in vitro as well as murine CT26 tumour angiogenesis without side effects, showing good potential (Raffaniello et al, 2009).…”

Yersinia enterocolitica Inhibits Salmonella enterica Serovar Typhimurium and Listeria monocytogenes Cellular Uptake

“…Typhimurium translocates effector proteins (SipA, SipC, SopE, SopE2, and SopB/SigD) into nonphagocytic cells via T3SS1 to induce a "triggering" mode of uptake, whereas Y. enterocolitica translocates effectors (YopE, YopH, YopO, and YopT) into phagocytic cells to inhibit its own uptake (17,19,25,29). When Y. enterocolitica is added to host cells first, S. Typhimurium invasion drops to a level similar to that of an S. Typhimurium invA mutant, which lacks T3SS1 (Fig.…”

“…1B is also a food-borne pathogen and, like S. Typhimurium, translocates numerous T3SS effector proteins, called Yops, into the host cell cytosol using both the Ysc T3SS encoded on the virulence plasmid, pYV, and the Ysa T3SS encoded on the chromosome (25)(26)(27)(28)(29). However, in contrast to S.…”