Mazar Joseph, Zhao Wei, Khalil Ahmad M, Lee Bongyong, Shelley John, Govindarajan Subramaniam S, Yamamoto Fumiko, Ratnam Maya, Aftab Muhammad Nauman, Collins Sheila, Finck Brian N, Han Xianlin, Mattick John S, Dinger Marcel E, Perera Ranjan J
Sanford-Burnham Medical Research Institute, Orlando, FL 32827, USA.
Department of Genetics and Genome Sciences, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA.
Oncotarget. 2014 Oct 15;5(19):8959-69. doi: 10.18632/oncotarget.1863.
Expression of the long noncoding RNA (lncRNA) SPRY4-IT1 is low in normal human melanocytes but high in melanoma cells. siRNA knockdown of SPRY4-IT1 blocks melanoma cell invasion and proliferation, and increases apoptosis. To investigate its function further, we affinity purified SPRY4-IT1 from melanoma cells and used mass spectrometry to identify the protein lipin 2, an enzyme that converts phosphatidate to diacylglycerol (DAG), as a major binding partner. SPRY4-IT1 knockdown increases the accumulation of lipin2 protein and upregulate the expression of diacylglycerol O-acyltransferase 2 (DGAT2) an enzyme involved in the conversion of DAG to triacylglycerol (TAG). When SPRY4-IT1 knockdown and control melanoma cells were subjected to shotgun lipidomics, an MS-based assay that permits the quantification of changes in the cellular lipid profile, we found that SPRY4-IT1 knockdown induced significant changes in a number of lipid species, including increased acyl carnitine, fatty acyl chains, and triacylglycerol (TAG). Together, these results suggest the possibility that SPRY4-IT1 knockdown may induce apoptosis via lipin 2-mediated alterations in lipid metabolism leading to cellular lipotoxicity.
长链非编码RNA（lncRNA）SPRY4-IT1在正常人黑素细胞中表达较低，但在黑色素瘤细胞中表达较高。SPRY4-IT1的siRNA敲低可阻断黑色素瘤细胞的侵袭和增殖，并增加细胞凋亡。为了进一步研究其功能，我们从黑色素瘤细胞中亲和纯化了SPRY4-IT1，并使用质谱法鉴定了蛋白脂联素2，一种将磷脂酸转化为二酰基甘油（DAG）的酶，作为主要结合伴侣。SPRY4-IT1敲低增加了脂联素2蛋白的积累，并上调了二酰基甘油O-酰基转移酶2（DGAT2）的表达，DGAT2是一种参与将DAG转化为三酰基甘油（TAG）的酶。当对SPRY4-IT1敲低和对照黑色素瘤细胞进行鸟枪法脂质组学分析时，这是一种基于质谱的测定方法，可对细胞脂质谱的变化进行定量，我们发现SPRY4-IT1敲低诱导了许多脂质种类的显著变化，包括酰基肉碱、脂肪酰链和三酰基甘油（TAG）的增加。总之，这些结果提示了SPRY4-IT1敲低可能通过脂联素2介导的脂质代谢改变导致细胞脂毒性从而诱导细胞凋亡的可能性。
