The Salmonella virulence protein SifA is a G protein antagonist
The Salmonella virulence protein SifA is a G protein antagonist
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DOI：
10.1073/pnas.0801872105
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发表时间：
2008-09-16
影响因子：
11.1
通讯作者：
Haldar, Kasturi
中科院分区：
文献类型：
--
作者：
Jackson, Laurie K.;Nawabi, Parwez;Haldar, Kasturi
沙门氏菌在细胞内增殖并引起疾病的成功取决于主要毒力蛋白 SifA 易位到宿主细胞中。 SifA 招募富含溶酶体相关膜蛋白 1 (LAMP1) 的膜，是沙门氏菌诱导的细丝 (Sifs) 和沙门氏菌含有液泡 (SCV) 生长所必需的。它直接结合称为 SKIP（SifA 和驱动蛋白相互作用蛋白）的宿主蛋白，这对于 SCV 的膜稳定性和运动动力学至关重要。 SifA 还包含 WxxxE 基序，可预测细菌效应子中的 G 蛋白模拟，但其是否以及如何模拟宿主 G 蛋白的作用尚不清楚。我们发现 SKIP 的 pleckstrin 同源结构域直接结合 SifA，也结合晚期内体 GTPase Rab9。敲低研究表明 SKIP 和 Rab9 都具有维持细胞外周 LAMP1 分布的功能。 Rab9:SKIP 相互作用是 GTP 依赖性的，并且被 SifA 与 SKIP pleckstrin 同源结构域的结合所抑制，表明 SifA 可能是 Rab9 拮抗剂。 SifA:SKIP 结合明显比 Rab9:SKIP 结合更紧密，因此可能允许 SifA 通过 SKIP 的 Rab9 结合位点将 SKIP 带到 SCV。 Rab9 可以显着逆转 SifA 依赖性 LAMP1 募集和细胞中 SCV 的核周位置。重要的是，与 SKIP 的结合需要保守的 WxxxE 特征序列的 SifA 残基 W197 和 E201，这导致人们推测细菌 G 蛋白拟态可能导致 G 蛋白拮抗作用。
Salmonella's success at proliferating intracellularly and causing disease depends on the translocation of a major virulence protein, SifA, into the host cell. SifA recruits membranes enriched in lysosome associated membrane protein 1 (LAMP1) and is needed for growth of Salmonella induced filaments (Sifs) and the Salmonella containing vacuole (SCV). It directly binds a host protein called SKIP(SifA and kinesin interacting protein)which is critical for membrane stability and motor dynamics at the SCV. SifA also contains a WxxxE motif, predictive of G protein mimicry in bacterial effectors, but whether and how it mimics the action of a host G protein is not known. We show that SKIP's pleckstrin homology domain, which directly binds SifA, also binds to the late endosomal GTPase Rab9. Knockdown studies suggest that both SKIP and Rab9 function to maintain peripheral LAMP1 distribution in cells. The Rab9:SKIP interaction is GTP-dependent and is inhibited by SifA binding to the SKIP pleckstrin homology domain, suggesting that SifA may be a Rab9 antagonist. SifA:SKIP binding is significantly tighter than Rab9:SKIP binding and may thus allow SifA to bring SKIP to the SCV via SKIP's Rab9-binding site. Rab9 can measurably reverse SifA-dependent LAMP1 recruitment and the perinuclear location of the SCV in cells. Importantly, binding to SKIP requires SifA residues W197 and E201 of the conserved WxxxE signature sequence, leading to the speculation that bacterial G protein mimicry may result in G protein antagonism.