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14-3-3 Binding and Sumoylation Concur to the Down-Modulation of β-catenin Antagonist chibby 1 in Chronic Myeloid Leukemia.

Mancini M, Leo E, Takemaru K, Campi V, Castagnetti F, Soverini S, De Benedittis C, Rosti G, Cavo M, Santucci MA, Martinelli G - PLoS ONE (2015)

Bottom Line: Here we demonstrate that it also arises from reduced protein stability upon binding to 14-3-3σ adapter protein.The ubiquitin proteasome system UPS participates in reducing stability of CBY1 bound with 14-3-3σ through enhanced SUMOylation.Our results open new routes towards the research on molecular pathways promoting the proliferative advantage of leukemic hematopoiesis over the normal counterpart.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Diagnostic and Specialty Medicine-DIMES-Institute of Hematology "L. and A. Seràgnoli". University of Bologna-Medical School, Bologna, Italy.

ABSTRACT
The down-modulation of the β-catenin antagonist Chibby 1 (CBY1) associated with the BCR-ABL1 fusion gene of chronic myeloid leukemia (CML) contributes to the aberrant activation of β-catenin, particularly in leukemic stem cells (LSC) resistant to tyrosine kinase (TK) inhibitors. It is, at least partly, driven by transcriptional events and gene promoter hyper-methylation. Here we demonstrate that it also arises from reduced protein stability upon binding to 14-3-3σ adapter protein. CBY1/14-3-3σ interaction in BCR-ABL1+ cells is mediated by the fusion protein TK and AKT phosphorylation of CBY1 at critical serine 20, and encompasses the 14-3-3σ binding modes I and II involved in the binding with client proteins. Moreover, it is impaired by c-Jun N-terminal kinase (JNK) phosphorylation of 14-3-3σ at serine 186, which promotes dissociation of client proteins. The ubiquitin proteasome system UPS participates in reducing stability of CBY1 bound with 14-3-3σ through enhanced SUMOylation. Our results open new routes towards the research on molecular pathways promoting the proliferative advantage of leukemic hematopoiesis over the normal counterpart.

No MeSH data available.


Related in: MedlinePlus

AKT inactivation in response to m-TOR inhibitor RAD001 hinders CBY1 interaction with 14-3-3σ and is associated with cytoplasmic CBY1 increment.A- RAD001 inhibits its target: AKT; B- CBY1 expression and interaction with 14-3-3σ and C- βcatenin expression and interaction with 14-3-3σ were assayed in the cytoplasmic and nuclear compartments of C22orf2 K562 cells at 24th hour of exposure to RAD001. The absence of off-target effects was assayed (Supplementary section, S2 Fig). See legend to Fig 1 for technical details.
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pone.0131074.g003: AKT inactivation in response to m-TOR inhibitor RAD001 hinders CBY1 interaction with 14-3-3σ and is associated with cytoplasmic CBY1 increment.A- RAD001 inhibits its target: AKT; B- CBY1 expression and interaction with 14-3-3σ and C- βcatenin expression and interaction with 14-3-3σ were assayed in the cytoplasmic and nuclear compartments of C22orf2 K562 cells at 24th hour of exposure to RAD001. The absence of off-target effects was assayed (Supplementary section, S2 Fig). See legend to Fig 1 for technical details.

Mentions: RAD001 (everolimus), an mTOR inhibitor promoting persistent AKT inactivation, was used to investigate the impact of AKT inhibition on CBY1 and βcatenin subcellular localization and expression in relation to their interaction with 14-3-3σ [25]. The absence of RAD001 off-target effects in C22orf2 K562 cell line was preliminary assayed (Supplementary section, S3 Fig). Persistent AKT de-phosphorylation at serine 473 upon treatment with RAD001 was associated with a significant reduction of CBY1 interaction with 14-3-3σ in the cytoplasm (p<0.01) and its complete abolition in the nuclear compartment of C22orf2 K562 cells (Fig 3A and 3B). CBY1 release from 14-3-3σ in response to RAD001 was associated with a significant increase of CBY1 levels in the cytoplasm (p<0.01), but not in the nucleus (p<0.1) (Fig 3B). The increment of cytoplasmic CBY1 in response to RAD001 was not driven by enhanced transcription (data not shown). It might be ascribed to enhanced stability, while CBY1 steady levels in the nucleus might be attributed to impaired nuclear export due to AKT inhibition. βcatenin expression and interaction with 14-3-3σ were similarly reduced in response to RAD001 in both compartments (p<0.05), further supporting the role of 14-3-3σ binding in protecting βcatenin from degradation and preventing nuclear re-import in the presence of activated BCR-ABL1 TK (Fig 3C).


14-3-3 Binding and Sumoylation Concur to the Down-Modulation of β-catenin Antagonist chibby 1 in Chronic Myeloid Leukemia.

Mancini M, Leo E, Takemaru K, Campi V, Castagnetti F, Soverini S, De Benedittis C, Rosti G, Cavo M, Santucci MA, Martinelli G - PLoS ONE (2015)

AKT inactivation in response to m-TOR inhibitor RAD001 hinders CBY1 interaction with 14-3-3σ and is associated with cytoplasmic CBY1 increment.A- RAD001 inhibits its target: AKT; B- CBY1 expression and interaction with 14-3-3σ and C- βcatenin expression and interaction with 14-3-3σ were assayed in the cytoplasmic and nuclear compartments of C22orf2 K562 cells at 24th hour of exposure to RAD001. The absence of off-target effects was assayed (Supplementary section, S2 Fig). See legend to Fig 1 for technical details.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4492953&req=5

pone.0131074.g003: AKT inactivation in response to m-TOR inhibitor RAD001 hinders CBY1 interaction with 14-3-3σ and is associated with cytoplasmic CBY1 increment.A- RAD001 inhibits its target: AKT; B- CBY1 expression and interaction with 14-3-3σ and C- βcatenin expression and interaction with 14-3-3σ were assayed in the cytoplasmic and nuclear compartments of C22orf2 K562 cells at 24th hour of exposure to RAD001. The absence of off-target effects was assayed (Supplementary section, S2 Fig). See legend to Fig 1 for technical details.
Mentions: RAD001 (everolimus), an mTOR inhibitor promoting persistent AKT inactivation, was used to investigate the impact of AKT inhibition on CBY1 and βcatenin subcellular localization and expression in relation to their interaction with 14-3-3σ [25]. The absence of RAD001 off-target effects in C22orf2 K562 cell line was preliminary assayed (Supplementary section, S3 Fig). Persistent AKT de-phosphorylation at serine 473 upon treatment with RAD001 was associated with a significant reduction of CBY1 interaction with 14-3-3σ in the cytoplasm (p<0.01) and its complete abolition in the nuclear compartment of C22orf2 K562 cells (Fig 3A and 3B). CBY1 release from 14-3-3σ in response to RAD001 was associated with a significant increase of CBY1 levels in the cytoplasm (p<0.01), but not in the nucleus (p<0.1) (Fig 3B). The increment of cytoplasmic CBY1 in response to RAD001 was not driven by enhanced transcription (data not shown). It might be ascribed to enhanced stability, while CBY1 steady levels in the nucleus might be attributed to impaired nuclear export due to AKT inhibition. βcatenin expression and interaction with 14-3-3σ were similarly reduced in response to RAD001 in both compartments (p<0.05), further supporting the role of 14-3-3σ binding in protecting βcatenin from degradation and preventing nuclear re-import in the presence of activated BCR-ABL1 TK (Fig 3C).

Bottom Line: Here we demonstrate that it also arises from reduced protein stability upon binding to 14-3-3σ adapter protein.The ubiquitin proteasome system UPS participates in reducing stability of CBY1 bound with 14-3-3σ through enhanced SUMOylation.Our results open new routes towards the research on molecular pathways promoting the proliferative advantage of leukemic hematopoiesis over the normal counterpart.

View Article: PubMed Central - PubMed

Affiliation: Department of Experimental Diagnostic and Specialty Medicine-DIMES-Institute of Hematology "L. and A. Seràgnoli". University of Bologna-Medical School, Bologna, Italy.

ABSTRACT
The down-modulation of the β-catenin antagonist Chibby 1 (CBY1) associated with the BCR-ABL1 fusion gene of chronic myeloid leukemia (CML) contributes to the aberrant activation of β-catenin, particularly in leukemic stem cells (LSC) resistant to tyrosine kinase (TK) inhibitors. It is, at least partly, driven by transcriptional events and gene promoter hyper-methylation. Here we demonstrate that it also arises from reduced protein stability upon binding to 14-3-3σ adapter protein. CBY1/14-3-3σ interaction in BCR-ABL1+ cells is mediated by the fusion protein TK and AKT phosphorylation of CBY1 at critical serine 20, and encompasses the 14-3-3σ binding modes I and II involved in the binding with client proteins. Moreover, it is impaired by c-Jun N-terminal kinase (JNK) phosphorylation of 14-3-3σ at serine 186, which promotes dissociation of client proteins. The ubiquitin proteasome system UPS participates in reducing stability of CBY1 bound with 14-3-3σ through enhanced SUMOylation. Our results open new routes towards the research on molecular pathways promoting the proliferative advantage of leukemic hematopoiesis over the normal counterpart.

No MeSH data available.


Related in: MedlinePlus