Phosphatidylserine acyl chain remodeling regulates KRAS spatial distribution and function on the plasma membrane.

项目总结： KRAS Small GTPase激活丝裂原活化蛋白激酶(MAPKs)，参与细胞增殖。 KRAS是癌症中突变最多的蛋白之一，其突变存在于98%-45%的胰腺肿瘤中 结直肠肿瘤和31%的肺部肿瘤。尽管经过几十年的集中关注，我们仍然没有任何有效的 抑制KRAS肿瘤发生的方法。KRAS功能主要被划分为细胞质 膜(PM)，在那里KRAS与一组选定的脂类相互作用，形成效应器的信号纳米簇 招募和信号转导。我们最近发现，KRAS纳米团簇特别富含 混链磷脂酰丝氨酸(PS)物种。因此，KRAS纳米聚集和效应器结合 在混合链PS存在下选择性地发生。因此，KRAS函数依赖于PS酰基链 结构。在这里，我们建议使用溶血磷脂酰胆碱酰基转移酶来调节PS酰链 (LPCATS)。特别是，我们现在表明，增加LPCAT1水平减少了主要的混合链PS物种 人胰腺肿瘤细胞，并破坏KRAS在PM上的纳米聚集这一点进一步得到了 癌症患者数据显示，依赖KRAS的胰腺癌或肺癌患者体内含量较低 LPCAT1。LPCAT的另一个成员，LPCAT4，升高混合链脂类，并已被证明促进 KRAS在患者中的致癌作用。我们假设，通过改变混合链PS的比例 物种、LPCAT1和LPCAT4调控KRAS纳米聚集和功能。对我们的成功测试 假说可能为KRAS依赖患者提供另一种扰乱KRAS病理的策略 肿瘤。我们的假设基于一个公认的前提：KRAS纳米聚集和功能选择性 依赖于混合链PS物种，其丰度受LPCAT1/4调节。为了验证我们的假设， 我们提出了三个具体目标。在目标1中，我们将检查LPCAT1/4改变的脂质组学与 LPCAT1/4对对KRAS功能至关重要的PM特性有影响的全细胞、PM和内膜。在……里面 目的2，研究LPCAT1/4调控KRAS空间分布的分子机制， 可能通过重塑PS酰基链来实现。在目标3中，我们将研究LPCAT1/4如何 在哺乳动物和人类肿瘤系队列中调节KRAS功能，以及在活体线虫病中 Elgans(已建立的研究KRAS肿瘤发生的模型系统)。在这里，我们建议严格审查一个 LPCATS重塑PS酰链轮廓调控KRAS时空分布的新机制 组织、信号和功能。我们的目标是测试LPCATs作为KRAS肿瘤发生的新调节因子。 生物学上，尽管脂酰链对各种重要的脂双层性质有贡献，但 细胞中的酰基链通常包含数千种脂类，目前还没有被很好地理解。我们的 所提出的机制将有助于我们理解脂酰链的潜在生物学作用。

Project Summary: KRAS small GTPase activates mitogen-activated protein kinases (MAPKs) and participates in cell proliferation. KRAS is one of the most mutated proteins in cancer, with its mutations found in 98% of pancreatic tumors, 45% of colorectal tumors and 31% of lung tumors. Despite decades of intense focus, we still do not have any effective means of inhibiting KRAS oncogenesis. KRAS function is mostly compartmentalized to the cell plasma membrane (PM), where KRAS interacts with a select set of lipids to form signaling nanoclusters for effector recruitment and signal transduction. We recently showed that KRAS nanoclusters are specifically enriched with the mixed-chain phosphatidylserine (PS) species. In consequence, KRAS nanoclustering and effector binding occur selectively in the presence of the mixed-chain PS. Thus, KRAS function depends on PS acyl chain structures. We, here, propose to modulate PS acyl chains using lysophosphatidylcholine acyltransferases (LPCATs). In particular, we now show that increasing LPCAT1 levels reduces major mixed-chain PS species in human pancreatic tumor cells, and disrupts the nanoclustering of KRAS on the PM. This is further supported by cancer patient data showing that patients with KRAS-dependent pancreatic or lung cancer contain lower levels of LPCAT1. Another LPCAT member, LPCAT4, elevates the mixed-chain lipids and has been shown to promote KRAS oncogenesis in patients. We hypothesize that, by shifting the proportions of the mixed-chain PS species, LPCAT1 and LPCAT4 modulate KRAS nanoclustering and function. A successful testing of our hypothesis may provide an alternative strategy for perturbing KRAS pathology for patients with KRAS-dependent tumors. Our hypothesis is based on a well-established premise: KRAS nanoclustering and function selectiveluy depend on the mixed-chain PS species, whose abundance is modulated by LPCAT1/4. To test our hypothesis, we propose 3 Specific Aims. In Aim 1, we will examine a correlation between LPCAT1/4-altered lipidomics in whole-cell, the PM and endomembrane with effects of LPCAT1/4 on PM properties critical to KRAS function. In Aim 2, we will examine a molecular mechanism, by which LPCAT1/4 regulate spatial distribution of KRAS, potentially via remodeling PS acyl chains. In Aim 3, we will examine a molecular mechanism for how LPCAT1/4 modulate KRAS function in a cohort of mammalian and human tumor lines, as well as in vivo Caenorhabditis elegans (established model system for studying KRAS oncogenesis). Here, we propose to rigorously examine a novel mechanism, whereby remodeling PS acyl chain profiles by LPCATs modulates KRAS spatiotemporal organization, signaling and function. We aim to test LPCATs as novel regulators of KRAS oncogenesis. Biologically, although lipid acyl chains contribute to various important lipid bilayer properties, the importance of acyl chains in cells, which typically contain thousands of lipid species, has not been well-understood. Our proposed mechanism will contribute to our understanding of the potential biological roles of lipid acyl chain.