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Adapter Protein SH2-Bβ Stimulates Actin-Based Motility of Listeria monocytogenes in a Vasodilator-Stimulated Phosphoprotein (VASP)-Dependent Fashion

Diakonova, Maria, Helfer, Emmanuele, Seveau, Stephanie, Swanson, Joel A., Kocks, Christine, Rui, Liangyou, Carlier, Marie-France, Carter-Su, Christin
Infection and immunity 2007 v.75 no.7 pp. 3581-3593
Listeria monocytogenes, actin, biomimetics, cell movement, eukaryotic cells, fibroblasts, mice, recruitment
SH2-Bβ (Src homology 2 Bβ) is an adapter protein that is required for maximal growth hormone-dependent actin reorganization in membrane ruffling and cell motility. Here we show that SH2-Bβ is also required for maximal actin-based motility of Listeria monocytogenes. SH2-Bβ localizes to Listeria-induced actin tails and increases the rate of bacterial propulsion in infected cells and in cell extracts. Furthermore, Listeria motility is decreased in mouse embryo fibroblasts from SH2-B⁻/⁻ mice. Both recruitment of SH2-Bβ to Listeria and SH2-Bβ stimulation of actin-based propulsion require the vasodilator-stimulated phosphoprotein (VASP), which binds ActA at the surfaces of Listeria cells and enhances bacterial actin-based motility. SH2-Bβ enhances actin-based movement of ActA-coated beads in a biomimetic actin-based motility assay, provided that VASP is present. In vitro binding assays show that SH2-Bβ binds ActA but not VASP; however, binding to ActA is greater in the presence of VASP. Because VASP also plays an essential regulatory role in actin-based processes in eukaryotic cells, the present results provide mechanistic insight into the functions of both SH2-Bβ and VASP in motility and also increase our understanding of the fundamental mechanism by which Listeria spreads.