The alternative splicing repressors hnRNP A1/A2 and PTB influence pyruvate kinase isoform expression and cell metabolism
The alternative splicing repressors hnRNP A1/A2 and PTB influence pyruvate kinase isoform expression and cell metabolism
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DOI：
10.1073/pnas.0914845107
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发表时间：
2010-02-02
影响因子：
11.1
通讯作者：
Krainer, Adrian R.
中科院分区：
文献类型：
--
作者：
Clower, Cynthia V.;Chatterjee, Deblina;Krainer, Adrian R.
癌细胞优先通过有氧糖酵解代谢葡萄糖，其特征在于乳酸产生增加。这种独特的代谢涉及丙酮酸激酶的胚胎M2同工酶的表达，与分化细胞中正常表达的M1同工酶相反，并且它赋予肿瘤细胞增殖优势。M1和M2腺苷酸激酶同工酶通过一对互斥外显子的选择性剪接从单个基因表达。我们测量了小鼠组织、肿瘤细胞系和肌细胞终末分化过程中M1和M2 mRNA和蛋白质亚型的表达，并表明选择性剪接调节足以解释表达的蛋白质亚型的水平。我们进一步表明，M1特异性外显子积极抑制在癌细胞系中，虽然一些M1 mRNA表达在来自脑肿瘤的细胞系中，并证明相关的剪接抑制hnRNP A1和A2，以及多嘧啶道结合蛋白PTB，有助于这种控制。在癌细胞系中使用shRNA下调这些剪接阻遏物可以挽救M1亚型的表达并降低乳酸产生的程度。这些发现扩展了选择性剪接和癌症之间的联系，并开始定义一些负责有氧糖酵解转换的因素。
Cancer cells preferentially metabolize glucose by aerobic glycolysis, characterized by increased lactate production. This distinctive metabolism involves expression of the embryonic M2 isozyme of pyruvate kinase, in contrast to the M1 isozyme normally expressed in differentiated cells, and it confers a proliferative advantage to tumor cells. The M1 and M2 pyruvate-kinase isozymes are expressed from a single gene through alternative splicing of a pair of mutually exclusive exons. We measured the expression of M1 and M2 mRNA and protein isoforms in mouse tissues, tumor cell lines, and during terminal differentiation of muscle cells, and show that alternative splicing regulation is sufficient to account for the levels of expressed protein isoforms. We further show that the M1-specific exon is actively repressed in cancer-cell lines-although some M1 mRNA is expressed in cell lines derived from brain tumors- and demonstrate that the related splicing repressors hnRNP A1 and A2, as well as the polypyrimidine-tract-binding protein PTB, contribute to this control. Downregulation of these splicing repressors in cancer-cell lines using shRNAs rescues M1 isoform expression and decreases the extent of lactate production. These findings extend the links between alternative splicing and cancer, and begin to define some of the factors responsible for the switch to aerobic glycolysis.