SH2-Bβ affects the length of Listeria actin tails. (A) COS-7 cells expressing the indicated proteins were infected with Listeria and stained for actin. Asterisks denote transfected cells. Arrows indicate Listeria actin tails. Bars, 10 μm. (B) GFP-SH2-Bβ (lane 1), GFP-SH2-Bβ(R555E) (lane 2), GFP-SH2-Bβ(1-555) (lane 3), GFP-SH2-Bβ(504-670) (lane 4), and GFP (lane 5) were overexpressed in COS-7 cells. GFP and GFP-tagged forms of SH2-Bβ were immunoprecipitated using anti-GFP and visualized by blotting with anti-GFP. The migration of GFP and GFP-tagged forms of SH2-Bβ is indicated. (C) Lengths of actin tails of Listeria in cells expressing the indicated forms of SH2-Bβ. n = 280, 117, 98, 95, 102, and 119 for nontransfected cells and cells expressing GFP, GFP-SH2-Bβ, GFP-SH2-Bβ(R555E), GFP-SH2-Bβ(1-555), and GFP-SH2-Bβ(504-670), respectively. (D) The number of Listeria organisms with actin tails as a percentage of Listeria organisms per cell was determined for cells expressing the indicated forms of GFP-SH2-Bβ. n = 24, 15, 21, 16, 18, and 25 for nontransfected cells and cells overexpressing GFP, GFP-SH2-Bβ, GFP-SH2-Bβ(R555E), GFP-SH2-Bβ(1-555), and GFP-SH2-Bβ(504-670), respectively. (E) COS-7 cells expressing the indicated GFP-tagged proteins (white) were infected with Listeria and stained with DAPI (blue) and phalloidin-Texas Red (not shown). Arrows indicate GFP-SH2-Bβ in long bacterial tails and GFP-tagged SH2-Bβ(R555E), SH2-Bβ(1-555), and SH2-Bβ(504-670) in short Listeria tails. *, plasma membrane. Bar, 5 μm. (F) The lengths of actin tails of Listeria were determined in MEF from SH2-B+/+ and SH2-B−/− mice. n = 245 for +/+ MEF and 344 for −/− MEF. The movement of bacteria in MEF from SH2-B+/+ (n = 123) and SH2-B−/− (n = 179) mice versus time was measured, and velocities were calculated. For panels C, D, and F, bars represent means plus SEM for three independent experiments. *, P < 0.05 compared to cells expressing GFP (B) or to MEF from SH2-B+/+ mice (F).