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Constitutive phosphorylation of the active Notch1 intracellular domain in chronic lymphocytic leukemia cells with NOTCH1 mutation

Leukemia volume 29, pages 994–998 (2015)Cite this article

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Alterations in Notch signaling are involved in chronic lymphocytic leukemia (CLL) pathogenesis, a hematological disease characterized by the accumulation of CD19+/CD5+ B cells resistant to apoptosis. We previously reported that constitutive Notch1/2 activation contributes to apoptosis resistance of CLL cells.1 Furthermore, a NOTCH1 PEST domain mutation, resulting in a truncated protein more stable and active than wild-type (WT) protein, has recently emerged as a recurrent genetic lesion in CLL patients with adverse prognosis and poor outcome.2, 3 Despite the progress achieved on the role of NOTCH1 mutations in CLL outcome, little is known regarding their role in CLL cell biology. There is evidence that NOTCH1 mutation stabilizes Notch1 signaling in CLL cells,4 but the molecular mechanisms underlying this effect remain to be defined.

Notch signaling is regulated by various posttranslational modifications including phosphorylation.5 Phosphorylation occurs in multiple sites within Notch-intracellular domain (ICD) and regulates Notch signaling at different levels. Phosphorylation of PEST domain targets Notch-ICD for proteasomal degradation, thereby attenuating its signaling,6 but phosphorylation in regions upstream of the PEST domain can either downregulate7, 8 or enhance9, 10 Notch signaling, and also mediate Notch-dependent oncogenesis.11 Here, we investigated whether the loss of PEST domain, by NOTCH1 mutation, alters the phosphorylation status of Notch1 protein and whether this event influences Notch1 activity and cell survival in CLL. Understanding how Notch signaling is regulated in NOTCH1-mutated CLL may provide important information to design new therapeutic strategies for these high-risk patients.

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Acknowledgements

This work was supported by grants from Progetti di Ricerca di Interesse Nazionale (PRIN 2010-2011; 2010MCLPLB_005 to E.R.), the Fondazione Cassa di Risparmio di Perugia, Italy (2012.0243.021 to E.R.) and the Associazione Italiana per la Ricerca sul Cancro (IG13314 to I.S.).

Author Contributions

FDF conceived and performed experiments and discussed data; RS, BDP and SB performed experiments and interpreted the data; FF, MDI and PS provided patient samples, patient clinical and laboratory data, and critical suggestions; IS and PM supervised the study and provided critical suggestions; ER conceived research, analyzed and interpreted data and wrote the manuscript. All authors revised the manuscript and approved the final version.

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Authors and Affiliations

  1. Department of Experimental Medicine, Biosciences and Medical Embryology Section, University of Perugia, Perugia, Italy

    F De Falco, R Sabatini, P Marconi & E Rosati

  2. Department of Medicine, Hematology and Clinical Immunology Section, University of Perugia, Perugia, Italy

    F Falzetti, P Sportoletti, S Baldoni & B Del Papa

  3. Department of Life, Health and Environmental Sciences, Hematology Section, University of L’Aquila, L’Aquila, Italy

    M Di Ianni

  4. Department of Molecular Medicine, University La Sapienza, Rome, Italy

    I Screpanti

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  1. F De Falco
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Correspondence to E Rosati.

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De Falco, F., Sabatini, R., Falzetti, F. et al. Constitutive phosphorylation of the active Notch1 intracellular domain in chronic lymphocytic leukemia cells with NOTCH1 mutation. Leukemia 29, 994–998 (2015). https://doi.org/10.1038/leu.2014.329

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