Diakonova Maria, Helfer Emmanuele, Seveau Stephanie, Swanson Joel A, Kocks Christine, Rui Liangyou, Carlier Marie-France, Carter-Su Christin
Department of Molecular and Integrative Physiology, University of Michigan Medical School, Ann Arbor, MI, USA.
Infect Immun. 2007 Jul;75(7):3581-93. doi: 10.1128/IAI.00214-07. Epub 2007 Apr 23.
SH2-Bbeta (Src homology 2 Bbeta) 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-Bbeta is also required for maximal actin-based motility of Listeria monocytogenes. SH2-Bbeta 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-Bbeta to Listeria and SH2-Bbeta 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-Bbeta 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-Bbeta 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-Bbeta and VASP in motility and also increase our understanding of the fundamental mechanism by which Listeria spreads.
SH2-Bβ（Src同源结构域2 Bβ）是一种衔接蛋白，在膜皱褶和细胞运动中，它是最大程度的生长激素依赖性肌动蛋白重组所必需的。在此我们表明，SH2-Bβ也是单核细胞增生李斯特菌最大程度的基于肌动蛋白的运动所必需的。SH2-Bβ定位于李斯特菌诱导的肌动蛋白尾，并提高感染细胞和细胞提取物中细菌推进的速率。此外，来自SH2-B（-/-）小鼠的小鼠胚胎成纤维细胞中李斯特菌的运动能力降低。SH2-Bβ募集到李斯特菌以及SH2-Bβ对基于肌动蛋白的推进的刺激都需要血管舒张刺激磷蛋白（VASP），VASP在李斯特菌细胞表面与ActA结合，并增强细菌基于肌动蛋白的运动。在存在VASP的情况下，SH2-Bβ在基于肌动蛋白的仿生运动试验中增强了ActA包被微珠的基于肌动蛋白的运动。体外结合试验表明，SH2-Bβ与ActA结合，但不与VASP结合；然而，在存在VASP的情况下与ActA的结合更强。由于VASP在真核细胞基于肌动蛋白的过程中也起着重要的调节作用，因此目前的结果为SH2-Bβ和VASP在运动中的功能提供了机制上的见解，也增加了我们对李斯特菌传播基本机制的理解。
