The alternative splicing repressors hnRNP A1/A2 and PTB influence pyruvate kinase isoform expression and cell metabolism.
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.
Clower
Cynthia V
CV
Division of Signal Transduction, Department of Systems Biology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02115, USA.
Chatterjee
Deblina
D
Wang
Zhenxun
Z
Cantley
Lewis C
LC
Vander Heiden
Matthew G
MG
Krainer
Adrian R
AR
D000332:Aerobiosis; D017398:Alternative Splicing; D000818:Animals; D002460:Cell Line; D045744:Cell Line, Tumor; D005091:Exons; D005909:Glioblastoma / Q000235:genetics / Q000378:metabolism; D006019:Glycolysis; D006367:HeLa Cells; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D019344:Lactic Acid / Q000096:biosynthesis; D051379:Mice; D038941:Polypyrimidine Tract-Binding Protein / Q000235:genetics / Q000378:metabolism; D011770:Pyruvate Kinase / Q000235:genetics* / Q000378:metabolism*; D022821:RNA Splice Sites; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism
D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D007527:Isoenzymes; D022821:RNA Splice Sites; D012333:RNA, Messenger; D012097:Repressor Proteins; C439768:hnRNP A2; D038941:Polypyrimidine Tract-Binding Protein; D019344:Lactic Acid; D011770:Pyruvate Kinase