Regulation of Nutrient Stress-Induced Macropinocytosis in Pancreatic Ductal Adenocarcinoma

项目摘要 近年来，人们越来越认识到代谢重编程在赋予人类细胞内的 对肿瘤细胞的生长和存活有利。与这一建议特别相关的是现在被广泛接受的 胰腺导管腺癌（PDAC）细胞依赖于巨胞饮作用作为氨基酸的概念 补给路线。通过刺激细胞外蛋白的摄取并将其靶向溶酶体降解， 巨胞饮途径为癌细胞提供蛋白质衍生的氨基酸来源， 以避免氨基酸耗尽并在营养胁迫下生存。谷氨酰胺是肿瘤的重要营养素， 支持维持肿瘤细胞生长所必需的代谢反应;然而， 肿瘤通常导致谷氨酰胺耗尽的肿瘤生态系统。我们之前资助的研究表明， PDAC肿瘤中的谷氨酰胺缺失具有调节巨胞饮作用的能力--使该过程加快， 按要求下。我们将这种可诱导的巨胞饮细胞摄取归因于EGFR-Pak的激活。 信号有趣的是，我们发现巨胞饮作用也是由谷氨酰胺结构类似物诱导的 广泛抑制谷氨酰胺代谢;然而，在这种情况下的吸收不利用EGFR信号传导。 由于谷氨酰胺代谢的抑制正被积极追求作为癌症的治疗，我们着手 解释谷氨酰胺模仿如何引起巨胞饮作为适应性反应。我们表演了一个高- 通过siRNA筛选并鉴定了激酶的非典型蛋白激酶C（aPKC）亚家族，PKC i和 蛋白激酶C（PKC）是最有效的摄取调节因子。这一提议是基于我们的初步数据， PKC β或PKC β的敲低不仅抑制由谷氨酰胺类似物引起的巨胞饮作用， 但也消除了谷氨酰胺饥饿引起的摄取，表明aPKC是通用调节剂， 营养胁迫诱导的巨胞饮作用基于这些数据，我们的中心假设是aPKC信号转导 是营养应激驱动的巨胞饮的组成部分，并且aPKC支持代谢应激耐受， PDAC肿瘤我们将1）研究aPKCs在营养胁迫中作用的分子机制- 驱动的巨胞饮作用和2）确定抑制aPKC依赖性 PDAC中的巨胞饮作用。该项目是对亚太维和中心在促进和平与安全方面所发挥作用的第一次评估。 调节巨胞饮作用，并首次从谷氨酰胺角度探讨aPKC功能 供应此外，由于我们的工作将建立aPKC依赖的巨胞饮作为一个关键的代谢， 适应响应谷氨酰胺模拟物，我们的研究结果可能会产生巨大的影响，发展 PDAC的新型治疗方法。

PROJECT SUMMARY Recent years have witnessed a growing appreciation of the role that metabolic reprogramming plays in conferring growth and survival advantages to tumor cells. Of particular relevance to this proposal is the now widely accepted notion that pancreatic ductal adenocarcinoma (PDAC) cells depend on macropinocytosis as an amino acid supply route. By stimulating the uptake of extracellular protein and targeting it for lysosomal degradation, the macropinocytosis pathway provides cancer cells with a source of protein-derived amino acids, allowing tumors to circumvent amino acid depletion and survive nutrient stress. Glutamine is a vital nutrient to tumors as it supports the metabolic reactions necessary to sustain tumor cell growth; however, hearty consumption by the tumor often leads to a glutamine-depleted tumor ecosystem. Our previously funded research demonstrated that glutamine depletion in PDAC tumors has the capacity to modulate macropinocytosis – dialing the process up or down as required. We attributed this inducible form of macropinocytic uptake to the activation of EGFR-Pak signaling. Interestingly, we have found that macropinocytosis is also induced by a glutamine structural analog that broadly suppresses glutamine metabolism; however, uptake in this setting does not employ EGFR signaling. Since the inhibition of glutamine metabolism is being actively pursued as a therapy for cancer, we set out to decipher how glutamine mimicry might elicit macropinocytosis as an adaptive response. We performed a high- throughput siRNA screen and identified the atypical protein kinase C (aPKC) subfamily of kinases, PKCι and PKCζ, as the most potent regulators of uptake. This proposal is based on our preliminary data demonstrating that knockdown of either PKCι or PKCζ not only suppresses macropinocytosis caused by glutamine analogs, but also abrogates uptake caused by glutamine starvation, suggesting that the aPKCs are general modulators of nutrient stress-induced macropinocytosis. Based on these data, our central hypothesis is that aPKC signaling is integral to nutrient stress-driven macropinocytosis and that the aPKCs support metabolic stress tolerance in PDAC tumors. We will 1) examine the molecular mechanisms underlying the role of aPKCs in nutrient stress- driven macropinocytosis and 2) determine the functional consequences of suppressing aPKC-dependent macropinocytosis in PDAC. This project constitutes the first evaluation of the role that the aPKCs play in the modulation of macropinocytosis and the first to interrogate aPKC function from the perspective of glutamine supply. Moreover, because our work will establish aPKC-dependent macropinocytosis as a critical metabolic adaptation in response to glutamine mimetics, our findings could have tremendous impact on the development of novel therapeutic modalities for PDAC.