Control of Pim2 kinase stability and expression in transformed human haematopoietic cells.
The oncogenic Pim2 kinase is overexpressed in several haematological malignancies, such as multiple myeloma and acute myeloid leukaemia (AML), and constitutes a strong therapeutic target candidate. Like other Pim kinases, Pim2 is constitutively active and is believed to be essentially regulated through its accumulation. We show that in leukaemic cells, the three Pim2 isoforms have dramatically short half-lives although the longer isoform is significantly more stable than the shorter isoforms. All isoforms present a cytoplasmic localization and their degradation was neither modified by broad-spectrum kinase or phosphatase inhibitors such as staurosporine or okadaic acid nor by specific inhibition of several intracellular signalling pathways including Erk, Akt and mTORC1. Pim2 degradation was inhibited by proteasome inhibitors but Pim2 ubiquitination was not detected even by blocking both proteasome activity and protein de-ubiquitinases (DUBs). Moreover, Pyr41, an ubiquitin-activating enzyme (E1) inhibitor, did not stabilize Pim2, strongly suggesting that Pim2 was degraded by the proteasome without ubiquitination. In agreement, we observed that purified 20S proteasome particles could degrade Pim2 molecule in vitro. Pim2 mRNA accumulation in UT7 cells was controlled by erythropoietin (Epo) through STAT5 transcription factors. In contrast, the translation of Pim2 mRNA was not regulated by mTORC1. Overall, our results suggest that Pim2 is only controlled by its mRNA accumulation level. Catalytically active Pim2 accumulated in proteasome inhibitor-treated myeloma cells. We show that Pim2 inhibitors and proteasome inhibitors, such as bortezomib, have additive effects to inhibit the growth of myeloma cells, suggesting that Pim2 could be an interesting target for the treatment of multiple myeloma.
Institut Cochin, INSERM U1016, CNRS UMR 8104, Université Paris Descartes, Sorbonne-Paris-Cité, Paris 75014, France Ligue Nationale Contre le Cancer, équipe labellisée, Paris 75014, France.
Kévin
K
Adam
Institut Cochin, INSERM U1016, CNRS UMR 8104, Université Paris Descartes, Sorbonne-Paris-Cité, Paris 75014, France Ligue Nationale Contre le Cancer, équipe labellisée, Paris 75014, France.
Mireille
M
Lambert
Institut Cochin, INSERM U1016, CNRS UMR 8104, Université Paris Descartes, Sorbonne-Paris-Cité, Paris 75014, France Ligue Nationale Contre le Cancer, équipe labellisée, Paris 75014, France.
Elsa
E
Lestang
Institut Cochin, INSERM U1016, CNRS UMR 8104, Université Paris Descartes, Sorbonne-Paris-Cité, Paris 75014, France.
Gabriel
G
Champenois
Institut Cochin, INSERM U1016, CNRS UMR 8104, Université Paris Descartes, Sorbonne-Paris-Cité, Paris 75014, France Ligue Nationale Contre le Cancer, équipe labellisée, Paris 75014, France.
Isabelle
I
Dusanter-Fourt
Institut Cochin, INSERM U1016, CNRS UMR 8104, Université Paris Descartes, Sorbonne-Paris-Cité, Paris 75014, France Ligue Nationale Contre le Cancer, équipe labellisée, Paris 75014, France Hopital Cochin, AP-HP, Paris 75014, France.
Jérôme
J
Tamburini
Institut Cochin, INSERM U1016, CNRS UMR 8104, Université Paris Descartes, Sorbonne-Paris-Cité, Paris 75014, France Ligue Nationale Contre le Cancer, équipe labellisée, Paris 75014, France Hopital Cochin, AP-HP, Paris 75014, France.
Didier
D
Bouscary
Institut Cochin, INSERM U1016, CNRS UMR 8104, Université Paris Descartes, Sorbonne-Paris-Cité, Paris 75014, France.
Catherine
C
Lacombe
Institut Cochin, INSERM U1016, CNRS UMR 8104, Université Paris Descartes, Sorbonne-Paris-Cité, Paris 75014, France.
Yael
Y
Zermati
Institut Cochin, INSERM U1016, CNRS UMR 8104, Université Paris Descartes, Sorbonne-Paris-Cité, Paris 75014, France Ligue Nationale Contre le Cancer, équipe labellisée, Paris 75014, France patrick.mayeux@inserm.fr.
Patrick
P
Mayeux
D045744:Cell Line, Tumor; D015973:Gene Expression Regulation, Leukemic / Q000187:drug effects; D006801:Humans; D000076222:Mechanistic Target of Rapamycin Complex 1; D009101:Multiple Myeloma / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D046912:Multiprotein Complexes / Q000235:genetics; D061988:Proteasome Inhibitors / Q000008:administration & dosage*; D020033:Protein Isoforms / Q000096:biosynthesis / Q000235:genetics; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D055550:Protein Stability / Q000187:drug effects; D059748:Proteolysis / Q000187:drug effects; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D050799:STAT5 Transcription Factor / Q000235:genetics; D058570:TOR Serine-Threonine Kinases / Q000235:genetics
D046912:Multiprotein Complexes; C490587:PIM2 protein, human; D061988:Proteasome Inhibitors; D020033:Protein Isoforms; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D050799:STAT5 Transcription Factor; D000076222:Mechanistic Target of Rapamycin Complex 1; D017346:Protein Serine-Threonine Kinases; D058570:TOR Serine-Threonine Kinases
leukaemia; multiple myeloma; proteasome; protein degradation; ubiquitin