Nuclear GTPase PIKE Regulation and Functions

描述（由申请人提供）：NGF （Nerve Growth Factor，神经生长因子）通过引发包括PI 3-激酶/Akt通路在内的多种信号级联来调节几种神经元的存活，该信号级联在这一过程中起着至关重要的作用。pi3 -激酶/Akt信号通过影响细胞质凋亡机制和介导参与细胞死亡和存活的基因表达来阻止细胞死亡。NGF诱导pi3 -激酶和Akt向细胞核转运，但对细胞核pi3 -激酶和Akt调控的机制知之甚少。阐明它们在神经元细胞死亡机制中的作用机制不仅有助于更好地理解神经系统的发育，而且有望为神经退行性疾病的治疗干预提供多点。我们之前已经证明，NGF处理激活了pi3k激酶增强子（PIKE），这是一种脑特异性核GTPase，随后介导核pi3k激酶的激活。我们还表明，NGF触发PLC-Y1易位到细胞核，在那里它与PIKE结合，并通过其SH3结构域作为PIKE的GEF（鸟嘌呤核苷酸交换因子）。然而，GTPase激活蛋白（GAP）调控PIKE GTPase的机制尚不清楚。最近，我们发现PIKE与Akt结合并增强其激酶活性，但PIKE相互作用并刺激Akt酶活性的机制尚不清楚。此外，这种相互作用的生物学后果尚不清楚。作为我们了解NGF信号级联在神经元分化、可塑性和细胞存活中的长期目标的一部分，在这项应用中，我们提出：1)确定GAP介导PIKE GTPase活性的机制；2)明确PIKE与Akt的相互作用以及PIKE对Akt激酶活性的影响；3)明确PIKE/Akt相互作用在NGF信号传导中的抗凋亡作用。

DESCRIPTION (provided by applicant): NGF (Nerve Growth Factor) regulates survival of several types of neurons by provoking a variety of signaling cascades including the PI 3-kinase/Akt pathway, which plays an essential role in this process. PI 3-kinase/Akt signaling blocks cell death by both impinging on the cytoplasmic apoptotic machinery and by mediating the expression of genes involved in cell death and survival. NGF elicits translocation of both PI 3-kinase and Akt to the nucleus, but little is known about the mechanisms of nuclear PI 3-kinase and Akt regulation. Elucidation of their mechanisms of action in the cell death machinery in neurons not only leads to a better understanding of nervous system development but also promises to provide multiple points of therapeutic intervention for neurodegenerative diseases. We have previously demonstrated that NGF treatment activates PIKE (PI 3-kinase Enhancer), a brain specific nuclear GTPase, which subsequently mediates activation of the nuclear PI 3-kinase. We have also shown that NGF triggers the translocation of PLC-Y1 to the nucleus, where it binds to PIKE and acts as a GEF (Guanine nucleotide Exchange Factor) for PIKE through its SH3 domain. However, the mechanism of PIKE GTPase regulation by GAP (GTPase Activating Protein) remains obscure. Recently, we found that PIKE binds to Akt and enhances its kinase activity, but the mechanisms by which PIKE interacts and stimulates Akt enzymatic activity remain elusive. Moreover, the biological consequences of this interaction are unclear. As a part of our long-term goal to understand NGF signaling cascades in neuronal differentiation, plasticity and cell survival, in this application we propose: 1) To determine the mechanism by which GAP mediates PIKE GTPase activity; 2) To define the interaction between PIKE and Akt and the effects of PIKE on Akt kinase activity; 3) To define the anti-apoptotic effects of PIKE/Akt interaction in NGF signaling.