14-3-3 Integrates prosurvival signals mediated by the AKT and MAPK pathways in ZNF198- FGFR1-transformed hematopoietic cells
ABSTRACT Human 8p11 stem cell leukemia/lymphoma syndrome usually presents as a myeloproliferative disorder (MPD) that evolves to acute myeloid leukemia and/or lymphoma. The syndrome associated with t(8;13)(p11;q12) results in expression of the ZNF198-FGFR1 fusion tyrosine kinase that plays a pathogenic role in hematopoietic transformation. We found that ZNF198-FGFR1 activated both the AKT and mitogen activated protein kinase (MAPK) prosurvival signaling pathways, resulting in elevated phosphorylation of the AKT target FOXO3a at T32 and BAD at S112, respectively. These phosphorylated residues subsequently sequestered the proapoptotic FOXO3a and BAD to 14-3-3 to prevent apoptosis. We used a peptide-based 14-3-3 competitive antagonist, R18, to disrupt 14-3-3-ligand association. Expression of R18 effectively induced apoptosis in hematopoietic Ba/F3 cells transformed by ZNF198-FGFR1 compared with control cells. Moreover, purified recombinant transactivator of transcription (TAT)-conjugated R18 proteins effectively transduced into human leukemia cells and induced significant apoptosis in KG-1a cells expressing FGFR1OP2-FGFR1 fusion tyrosine kinase but not in control HL-60 and Jurkat T cells. Surprisingly, R18 was only able to dissociate FOXO3a, but not BAD as previously proposed, from 14-3-3 binding and induced apoptosis partially through liberation and reactivation of FOXO3a. Our findings suggest that 14-3-3 integrates prosurvival signals in FGFR1 fusion-transformed hematopoietic cells. Disrupting 14-3-3-ligand association may represent an effective therapeutic strategy to treat 8p11 stem cell MPD.
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- "Yorkie, a critical effector of the Hpo pathway, is not a direct transcriptional factor but is a potent transcriptional co-activator cooperating with different DNA binding proteins. Wts phosphorylates Yki at Ser 168, thus creating a binding site for 14-3-3 proteins, which in turn sequester Yki in the cytoplasm and prevent its nuclear import (Dong et al., 2007b; Oh and Irvine, 2008). Loss of Hpo signaling, as well as mutations in the 14-3-3 binding site for Yki, were shown to produce strong nuclear accumulation coupled with enhanced activity of Yki (Zhao et al., 2007). "
ABSTRACT: Growth arrest, inhibition of cell proliferation, apoptosis, senescence, and differentiation are the most characterized effects of a given tumor suppressor response. It is becoming increasingly clear that tumor suppression results from the integrated and synergistic activities of different pathways. This implies that tumor suppression includes linear, as well as lateral, crosstalk signaling. The latter may happen through the concomitant involvement of common nodal proteins. Here, we discuss the role of Promyelocytic leukemia protein (PML) in functional cross-talks with the HIPPO and the p53 family tumor suppressor pathways. PML, in addition to its own anti-tumor activity, contributes to the assembly of an integrated and superior network that may be necessary for the maximization of the tumor suppressor response to diverse oncogenic insults.Frontiers in Oncology 03/2013; 3:36. DOI:10.3389/fonc.2013.00036
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- "Yki is not a direct transcriptional factor because it does not possess its own consensus DNA-binding motif but is known as a potent transcriptional co-activator by cooperating with different DNA-binding proteins. Wts directly phosphorylates Yki at Ser 168, thus creating a binding site for 14-3-3 proteins which sequester Yki in the cytoplasm and prevent its nuclear import [44, 45]. In actual fact, the loss of Hippo signaling as well as mutations in 14-3-3 binding site for Yki was shown to produce strong nuclear accumulation, a common feature, coupled with aberrant activity of Yki . "
ABSTRACT: First discovered in Drosophila, the Hippo pathway regulates the size and shape of organ development. Its discovery and study have helped to address longstanding questions in developmental biology. Central to this pathway is a kinase cascade leading from the tumor suppressor Hippo (Mst1 and Mst2 in mammals) to the Yki protein (YAP and TAZ in mammals), a transcriptional coactivator of target genes involved in cell proliferation, survival, and apoptosis. A dysfunction of the Hippo pathway activity is frequently detected in human cancers. Recent studies have highlighted that the Hippo pathway may play an important role in tissue homoeostasis through the regulation of stem cells, cell differentiation, and tissue regeneration. Recently, the impact of RASSF proteins on Hippo signaling potentiating its proapoptotic activity has been addressed, thus, providing further evidence for Hippo's key role in mammalian tumorigenesis as well as other important diseases.07/2012; 2012(5):307628. DOI:10.1155/2012/307628
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- "The 14-3-3 proteins have raised to a position of integrators of diverse signaling cues that impact cell fate and cancer development . Through regulated interactions with crucial signaling mediators, such as PKC  , MAPK   , or AKT   , 14-3-3 controls diverse cellular responses ranging from signal transduction, cell cycle, metabolism, and apoptosis . Among seven 14-3-3 proteins, 14-3-3ζ, also termed as YWHAZ (tyrosine 3-monooxygenase/tryptophan 5- monooxygenase activation protein, zeta polypeptide), has been shown to play a central role regulating multiple pathways responsible for cancer initiation and progression . "
ABSTRACT: Signal transducers and activators of transcription 3 (Stat3) has been reported to be involved in the pathogenesis of various human diseases and is constitutively active in human multiple myeloma (MM) U266 cells. The Stat3-regulated mechanisms involved in these processes, however, are not fully defined. To further understand the regulation of Stat3 activity, we performed a systematic proteomic analysis of Stat3 interacting proteins in U266 cells. This analysis, termed quantitative immunoprecipitation combined with knockdown (QUICK), combines RNAi, stable isotope labeling with amino acids in cell culture (SILAC), immunoprecipitation, and quantitative MS. As a result, quantitative mass spectrometry analysis allowed us to distinguish specific Stat3 interacting proteins from background proteins and led to the identification of a total of 38 proteins. Three Stat3 interacting proteins - 14-3-3ζ, PRKCB and Hsp90 - were further confirmed by reciprocal co-immunoprecipitations and surface plasmon resonance (SPR) analysis. Our results therefore not only uncover a number of Stat3 interacting proteins that possess a variety of cellular functions, but also provide new insight into the mechanisms that regulate Stat3 activity and function in MM cells.Journal of proteomics 10/2011; 75(3):1055-66. DOI:10.1016/j.jprot.2011.10.020 · 3.89 Impact Factor