Agonist Activated Phosphoinositide Kinase Scaffolds Control Motility and Survival Signals

PI3K/Akt信号在免疫系统、心血管和神经疾病以及癌症中起着重要作用。 它是癌症中最常见的解除调控的信号通路，具有治疗靶点。我们展示了 多结构域支架癌蛋白IQGAP1为肿瘤细胞的组装提供了新的分子平台。 PI4P-、PI4、5P2-和PI3、4、5P3产生酶(PI4KIIIα、PIPKIα和PI3K)。如此近距离的距离使得 为了协调和有效地产生PI3，4，5P3脂质信使，激活也相关的 PDK1/Akt激酶。包括整合素、受体酪氨酸激酶和G蛋白偶联在内的多种激动剂 受体刺激这个支架。重要的是，这种支架似乎对癌细胞的生存至关重要，揭示了一种 磷脂酰肌醇信号转导网络被癌细胞用来维持生存。IQGAP1与PI3K和 PIPKIα通过其WW和IQ子域。破坏这种IQGAP1支架会废除PI3，4，5P3的生成和 AKT激活并选择性地阻断癌细胞的存活。这表明协调的PI3，4，5P3合成 通过IQGAP1支架在癌细胞中激活PDK1和Akt为新的治疗打开了大门 肿瘤中针对PI3K/Akt信号转导的策略。此外，IQGAP2还具有肿瘤抑制活性，并与 PIPn激酶在相同的通路中阻断Akt的激活。 假设：在激动剂刺激下，IQGAP1支架使磷酸肌醇激酶协同产生 PI3，4，5P3脂信使，形成自成一体的PI3K/Akt信号平台。有选择地整合 PIPKI异构体(如PIPKIα与PIPKIγ)进入IQGAP1支架及其对PI4、5P2和/或PI3、4、5P3的调控 生成和下游激活控制不同的过程，包括细胞增殖、存活、侵袭 和能动性。IQGAP2与PIPn激酶结合可阻断PIPn激酶的促癌活性。这 我们将以以下目的对假说进行质疑： 目的1.EGF刺激如何特异性组装IQGAP1-PI3K支架？(A)酪氨酸的作用 磷酸化，(B)定义相互作用部位，底物通道，并识别失去结合和 研究致癌PI3K突变体的整合，以及(C)检查这些突变体是否需要EGFR信号。 目的2.研究EGFR和小G蛋白在迁移过程中对IQGAP1-PIPn激酶支架的调节作用 和入侵。(A)IQGAP1-PI3K支架在细胞运动中的作用，(B)IQGAP1-PIPKIγ支架在 EGFR和整合素在EGF刺激的迁移和侵袭中的贩运，(C)Arf6和rac1中的IQGAP1 (D)研究PIPn与IQGAP1结合在空间靶向、生存和侵袭中的作用。 目的3.研究IQGAP2-磷脂酰肌醇激酶支架作为肿瘤抑制因子的作用。(A)研究 将开发磷脂酰肌醇与IQGAP2和多肽抑制剂的相互作用，(B)定义 IQGAP2如何阻止Akt激活的机制，(C)操纵IQGAP2的表达以检查 PI3K信号与生物学。

PI3K/Akt signaling is fundamental in the immune system, cardiovascular and neuronal diseases, and cancers. It is the most commonly deregulated signaling pathway in cancers and is therapeutically targeted. We show that the multi-domain scaffolding oncoprotein, IQGAP1 provides a novel molecular platform for assembly of PI4P-, PI4,5P2- and PI3,4,5P3-generating enzymes (PI4KIIIα, PIPKIα and PI3K). This close proximity allows for concerted and efficient generation of the PI3,4,5P3 lipid messenger that activates the also associated PDK1/Akt kinases. Multiple agonists including integrins, receptor tyrosine kinases and G-protein coupled receptors stimulate this scaffold. Importantly, this scaffold appears crucial for cancer cell survival, uncovering a phosphoinositide signaling nexus utilized by cancer cells for their survival. IQGAP1 associates with PI3K and PIPKIα via its WW and IQ sub-domains. Disrupting this IQGAP1 scaffold abrogates PI3,4,5P3 generation and Akt activation and selectively blocks survival of cancer cells. This indicates that concerted PI3,4,5P3 synthesis with PDK1 and Akt activation in cancer cells via the IQGAP1 scaffold opens the door for novel therapeutic strategy targeting PI3K/Akt signaling in cancers. Further, IQGAP2 has tumor suppressor activity and also binds the PIPn kinases blocks Akt activation within the same pathways. Hypothesis: Upon agonist stimulation, IQGAP1 scaffolds phosphoinositide kinases for concerted production of the PI3,4,5P3 lipid messenger, leading to self-contained PI3K/Akt signaling platform. Selective integration of PIPKI isoforms (e.g. PIPKIα vs. PIPKIγ) into IQGAP1 scaffolds and their regulation of PI4,5P2 and/or PI3,4,5P3 generation and downstream activation controls distinct processes including cell proliferation, survival, invasion and motility. IQGAP2 binding to the PIPn kinases blocks the tumor promoting activity of the PIPn kinases. This hypothesis will be interrogated with the following aims: Aim 1. How does EGF-stimulation specifically assemble the IQGAP1-PI3K scaffold? (a) Role of tyrosine phosphorylation, (b) define interaction sites, substrate channeling, and identify mutants that lose binding and study integration of oncogenic PI3K mutants, and (c) examine if these require EGFR signaling. Aim 2. Study how EGFR and small G-proteins regulate IQGAP1-PIPn kinase scaffolds during migration and invasion. Roles of: (a) the IQGAP1-PI3K scaffold in cell motility, (b) the IQGAP1-PIPKIγ scaffold in trafficking of EGFR and integrins in EGF-stimulated migration and invasion, (c) IQGAP1 in Arf6 and Rac1 in control of invasion and (d) study the role of PIPn binding to IQGAP1 in spatial targeting, survival, and invasion. Aim 3. Investigate the IQGAP2-phosphoinositide kinase scaffold as a tumor suppressor. (a) Study interactions of phosphoinositide kinases with IQGAP2 and peptide inhibitors will be developed, (b) define the mechanism how IQGAP2 blocks Akt activation, (c) manipulate expression of IQGAP2 to examine roles in the PI3K signaling and biology.