Research Unit Functional Proteomics and Metabolic Pathways , Institute of Pathology, Medical University of Graz , 8010 Graz , Austria.
Omics Center Graz, BioTechMed-Graz , 8010 Graz , Austria.
J Proteome Res. 2018 Apr 6;17(4):1415-1425. doi: 10.1021/acs.jproteome.7b00782. Epub 2018 Mar 7.
Adipose triglyceride lipase (ATGL) catalyzes the rate limiting step in triacylglycerol breakdown in adipocytes but is expressed in most tissues. The enzyme was shown to be lost in many human tumors, and its loss may play a role in early stages of cancer development. Here, we report that loss of ATGL supports a more-aggressive cancer phenotype in a model system in which ATGL was deleted in A549 lung cancer cells by CRISPR/Cas9. We observed that loss of ATGL led to triacylglycerol accumulation in lipid droplets and higher levels of cellular phospholipid and bioactive lipid species (lyso- and ether-phospholipids). Label-free quantitative proteomics revealed elevated expression of the pro-oncogene SRC kinase in ATGL depleted cells, which was also found on mRNA level and confirmed on protein level by Western blot. Consistently, higher expression of phosphorylated (active) SRC (Y416 phospho-SRC) was observed in ATGL-KO cells. Cells depleted of ATGL migrated faster, which was dependent on SRC kinase activity. We propose that loss of ATGL may thus increase cancer aggressiveness by activation of pro-oncogenic signaling via SRC kinase and increased levels of bioactive lipids.
脂肪甘油三酯脂肪酶（ATGL）催化脂肪细胞中甘油三酯分解的限速步骤，但在大多数组织中表达。研究表明，该酶在许多人类肿瘤中丢失，其丢失可能在癌症发展的早期阶段发挥作用。在这里，我们报告说，在 ATGL 通过 CRISPR/Cas9 在 A549 肺癌细胞中缺失的模型系统中，ATGL 的缺失支持更具侵袭性的癌症表型。我们观察到 ATGL 的缺失导致脂滴中甘油三酯的积累，以及细胞磷脂和生物活性脂质（溶血磷脂和醚磷脂）水平的升高。无标记定量蛋白质组学显示，ATGL 耗尽细胞中原癌基因 SRC 激酶的表达上调，这在 mRNA 水平上也得到证实，并通过 Western blot 在蛋白质水平上得到证实。一致地，在 ATGL-KO 细胞中观察到磷酸化（活性）SRC（Y416 磷酸化 SRC）的表达升高。ATGL 耗尽的细胞迁移更快，这依赖于 SRC 激酶活性。因此，我们提出 ATGL 的缺失可能通过 SRC 激酶的原癌基因信号激活和生物活性脂质水平的增加来增加癌症的侵袭性。
