Negative feedback regulation of Rac in leukocytes from mice expressing a constitutively active phosphatidylinositol 3-kinase γ
Negative feedback regulation of Rac in leukocytes from mice expressing a constitutively active phosphatidylinositol 3-kinase γ
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DOI：
10.1073/pnas.0703175104
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发表时间：
2007-09-04
影响因子：
11.1
通讯作者：
Hirsch, Emilio
中科院分区：
文献类型：
--
作者：
Costa, Carlotta;Barberis, Laura;Hirsch, Emilio
趋化细胞的极化依赖于正反馈回路，该正反馈回路将趋化剂的浅梯度放大成尖锐的细胞内反应。特别地，磷脂酰肌醇3-激酶（PI 3 K）和小GTP酶如Rac的相互激活导致PI 3 K产物磷脂酰肌醇3，4，5-三磷酸（PIP 3）在前缘处的积累。携带G蛋白偶联受体（GPCR）激活的PI 3 K γ（编码质膜靶向蛋白）的“敲入”等位基因的小鼠似乎正常，但其白细胞显示GPCR未偶联的PIP 3蓄积。在体内，该突变增加了增殖并减少了凋亡，导致白细胞增多和伤口愈合中炎症的延迟消退。突变的白细胞表现出显着受损的定向细胞迁移反应的化学引诱剂。刺激的突变体巨噬细胞没有抑制PIP 3，并且由于RacGAP的PI 3 K依赖性活化增强而显示出缩短的Rac活化。连同化学引诱物刺激野生型巨噬细胞中的PIP 3依赖性GAP活化的发现，这些结果鉴定了涉及Rac的PI 3 K和RacGAP依赖性负控制的分子机制，其限制和微调促进细胞极化和定向运动的反馈回路。
Polarization of chernotaxing cells depends on positive feedback loops that amplify shallow gradients of chemoattractants into sharp intracellular responses. In particular, reciprocal activation of phosphaticlylinositol 3-kinases (PI3Ks) and small GTPases like Rac leads to accumulation, at the leading edge, of the PI3K product phosphaticlylinositol 3,4, 5-trisphosphate (PIP3). Mice carrying a "knockin" allele of the G protein-coupled receptor (GPCR)activated PI3K gamma, encoding a plasma membrane-targeted protein appeared normal, but their leukocytes showed GPCR-uncoupled PIP3 accumulation. In vivo, the mutation increased proliferation and decreased apoptosis, leading to leukocytosis and delayed resolution of inflammation in wound healing. Mutant leukocytes showed significantly impaired directional cell migration in response to chemoattractants. Stimulated mutant macrophages did not polarize PIP3 and showed a shortened Rac activation because of enhanced PI3K-dependent activation of RacGAPs. Together with the finding that chemoattractants stimulate a PIP3-dependent GAP activation in wild-type macrophages, these results identify a molecular mechanism involving PI3K- and RacGAP-dependent negative control of Rac that limits and fine-tunes feedback loops promoting cell polarization and directional motility.