Exon-centric regulation of pyruvate kinase M alternative splicing via mutually exclusive exons

Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
Journal of Molecular Cell Biology (Impact Factor: 6.77). 11/2011; 4(2):79-87. DOI: 10.1093/jmcb/mjr030
Source: PubMed


Alternative splicing of the pyruvate kinase M gene (PK-M) can generate the M2 isoform and promote aerobic glycolysis and tumor growth. However, the cancer-specific alternative splicing regulation of PK-M is not completely understood. Here, we demonstrate that PK-M is regulated by reciprocal effects on the mutually exclusive exons 9 and 10, such that exon 9 is repressed and exon 10 is activated in cancer cells. Strikingly, exonic, rather than intronic, cis-elements are key determinants of PK-M splicing isoform ratios. Using a systematic sub-exonic duplication approach, we identify a potent exonic splicing enhancer in exon 10, which differs from its homologous counterpart in exon 9 by only two nucleotides. We identify SRSF3 as one of the cognate factors, and show that this serine/arginine-rich protein activates exon 10 and mediates changes in glucose metabolism. These findings provide mechanistic insights into the complex regulation of alternative splicing of a key regulator of the Warburg effect, and also have implications for other genes with a similar pattern of alternative splicing.

Download full-text


Available from: Martin Akerman,
  • Source
    • "This mRNA species accounted for $40% of the PKM transcript in Pkm2 D/D tumors (Figure 2H), was identified by sequencing to result from the splicing of exon 8 to exon 11 (Figures S2D, S2F, S2G), and is hereafter referred to as PKM-skip. Splicing of PKM pre-mRNA to produce PKM2 transcript involves repression of exon 9 inclusion and activation of exon 10 inclusion by the binding of specific splicing factors to sequences within the alternatively spliced exons (Clower et al., 2010; David et al., 2010; Wang et al., 2012). Thus, the absence of exon 10 together with repression of exon 9 likely explains the presence of the PKM-skip mRNA species in Pkm2 D/D tumors (Chen et al., 2012). "
    [Show abstract] [Hide abstract]
    ABSTRACT: The pyruvate kinase M2 isoform (PKM2) is expressed in cancer and plays a role in regulating anabolic metabolism. To determine whether PKM2 is required for tumor formation or growth, we generated mice with a conditional allele that abolishes PKM2 expression without disrupting PKM1 expression. PKM2 deletion accelerated mammary tumor formation in a Brca1-loss-driven model of breast cancer. PKM2 null tumors displayed heterogeneous PKM1 expression, with PKM1 found in nonproliferating tumor cells and no detectable pyruvate kinase expression in proliferating cells. This suggests that PKM2 is not necessary for tumor cell proliferation and implies that the inactive state of PKM2 is associated with the proliferating cell population within tumors, whereas nonproliferating tumor cells require active pyruvate kinase. Consistent with these findings, variable PKM2 expression and heterozygous PKM2 mutations are found in human tumors. These data suggest that regulation of PKM2 activity supports the different metabolic requirements of proliferating and nonproliferating tumor cells. PAPERCLIP:
    Cell 10/2013; 155(2):397-409. DOI:10.1016/j.cell.2013.09.025 · 32.24 Impact Factor
    • "However, independent of their tissue of origin most cancer cells are PKM2 positive. Recent work showed how a mutually exclusive splicing event determines whether PKM2 is expressed and able to promote the Warburg effect.[56] Exon-blockage by heterogeneous nuclear ribonucleoproteins (hnRNPs) (PKM1-specific exon) in combination with serine/arginine-rich splicing factor 3 (SRSF3) binding to an exonic splicing enhancer (PKM2-specific exon), activates PKM1-specific exon exclusion and favors PKM2 production,[5–7] [Figure 1]. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Pyruvate kinase activity is controlled by a tightly woven regulatory network. The oncofetal isoform of pyruvate kinase (PKM2) is a master regulator of cancer metabolism. PKM2 engages in parallel, feed-forward, positive and negative feedback control contributing to cancer progression. Besides its metabolic role, non-metabolic functions of PKM2 as protein kinase and transcriptional coactivator for c-MYC and hypoxia-inducible factor 1-alpha are essential for epidermal growth factor receptor activation-induced tumorigenesis. These biochemical activities are controlled by a shift in the oligomeric state of PKM2 that includes acetylation, oxidation, phosphorylation, prolyl hydroxylation and sumoylation. Metabolically active PKM2 tetramer is allosterically regulated and responds to nutritional and stress signals. Metabolically inactive PKM2 dimer is imported into the nucleus and can function as protein kinase stimulating transcription. A systems biology approach to PKM2 at the genome, transcriptome, proteome, metabolome and fluxome level reveals how differences in biomolecular structure translate into a global rewiring of cancer metabolism. Cancer systems biology takes us beyond the Warburg effect, opening unprecedented therapeutic opportunities.
    Journal of Carcinogenesis 07/2013; 12(1):14. DOI:10.4103/1477-3163.115423
  • [Show abstract] [Hide abstract]
    ABSTRACT: Mitochondria are semi-autonomous organelles that play essential roles in cellular metabolism and programmed cell death pathways. Genomic, functional and structural mitochondrial alterations have been associated with cancer. Some of those alterations may provide a selective advantage to cells, allowing them to survive and grow under stresses created by oncogenesis. Due to the specific alterations that occur in cancer cell mitochondria, these organelles may provide promising targets for cancer therapy. The development of drugs that specifically target metabolic and mitochondrial alterations in tumor cells has become a matter of interest in recent years, with several molecules undergoing clinical trials. This review focuses on the most relevant mitochondrial alterations found in tumor cells, their contribution to cancer progression and survival, and potential usefulness for stratification and therapy.
    Biochimica et Biophysica Acta 04/2012; 1826(1):238-54. DOI:10.1016/j.bbcan.2012.04.005 · 4.66 Impact Factor
Show more