Project description:Deregulated RTK activity has been implicated as a causal leukemogenic factor in the context of molecular aberrations that perturb differentiation in the hematopoietic lineage such as in childhood ALL. A deeper understanding of RTK signaling processes on a system-wide scale will be key in defining critical components of signaling networks. To link RTK activity with in vivo output in primary ALL we took a functional approach, which combined SH2 domain binding, mass spectrometry, and transcriptome analyses. Structure and composition of evolving networks were highly diverse with few generic features determined by receptor and cell type. A combinatorial assembly of varying context-dependent and few generic signaling components at multiple levels likely generates output specificity. PAK2 was identified as a phosphoregulated FLT3 target, whose allosteric inhibition resulted in apoptosis of ALL cells. Our studies provide evidence that a functional approach to leukemia signaling may yield valuable information for a network-directed intervention. Primary ALL samples were investigated on Affymetrix SNP 6.0 arrays for copy-number changes related to receptor tyrosine kinases (RTKs). Buffy-Coat samples of healthy persons were used as reference.
Project description:Deregulated RTK activity has been implicated as a causal leukemogenic factor in the context of molecular aberrations that perturb differentiation in the hematopoietic lineage such as in childhood ALL. A deeper understanding of RTK signaling processes on a system-wide scale will be key in defining critical components of signaling networks. To link RTK activity with in vivo output in primary ALL we took a functional approach, which combined SH2 domain binding, mass spectrometry, and transcriptome analyses. Structure and composition of evolving networks were highly diverse with few generic features determined by receptor and cell type. A combinatorial assembly of varying context-dependent and few generic signaling components at multiple levels likely generates output specificity. PAK2 was identified as a phosphoregulated FLT3 target, whose allosteric inhibition resulted in apoptosis of ALL cells. Our studies provide evidence that a functional approach to leukemia signaling may yield valuable information for a network-directed intervention. Three different primary ALL samples expressing FLT3 and/or PDGFRß were stimulated with the corresponding ligands FLT3L and PDGF-BB for five time points. Unstimulated samples served as control. ALL22089 coexpresses FLT3 and PDGFRß. ALL109 expresses PDGFRß. ALL114 expresses FLT3.
Project description:Deregulated RTK activity has been implicated as a causal leukemogenic factor in the context of molecular aberrations that perturb differentiation in the hematopoietic lineage such as in childhood ALL. A deeper understanding of RTK signaling processes on a system-wide scale will be key in defining critical components of signaling networks. To link RTK activity with in vivo output in primary ALL we took a functional approach, which combined SH2 domain binding, mass spectrometry, and transcriptome analyses. Structure and composition of evolving networks were highly diverse with few generic features determined by receptor and cell type. A combinatorial assembly of varying context-dependent and few generic signaling components at multiple levels likely generates output specificity. PAK2 was identified as a phosphoregulated FLT3 target, whose allosteric inhibition resulted in apoptosis of ALL cells. Our studies provide evidence that a functional approach to leukemia signaling may yield valuable information for a network-directed intervention.
Project description:Deregulated RTK activity has been implicated as a causal leukemogenic factor in the context of molecular aberrations that perturb differentiation in the hematopoietic lineage such as in childhood ALL. A deeper understanding of RTK signaling processes on a system-wide scale will be key in defining critical components of signaling networks. To link RTK activity with in vivo output in primary ALL we took a functional approach, which combined SH2 domain binding, mass spectrometry, and transcriptome analyses. Structure and composition of evolving networks were highly diverse with few generic features determined by receptor and cell type. A combinatorial assembly of varying context-dependent and few generic signaling components at multiple levels likely generates output specificity. PAK2 was identified as a phosphoregulated FLT3 target, whose allosteric inhibition resulted in apoptosis of ALL cells. Our studies provide evidence that a functional approach to leukemia signaling may yield valuable information for a network-directed intervention.
Project description:Receptor tyrosine kinase (RTK)-dependent signaling has been implicated in the pathogenesis of acute lymphoblastic leukemia (ALL) of childhood. However, the RTK-dependent signaling state and its interpretation with regard to biological behavior are often elusive. To decipher signaling circuits that link RTK activity with biological output in vivo, we established patient-derived xenograft ALL (PDX-ALL) models with dependencies on fms-like tyrosine kinase 3 (FLT3) and platelet-derived growth factor receptor β (PDGFRB), which were interrogated by phosphoproteomics using iTRAQ mass spectrometry. Signaling circuits were determined by receptor type and cellular context with few generic features, among which we identified group I p21-activated kinases (PAKs) as potential therapeutic targets. Growth factor stimulation markedly increased catalytic activities of PAK1 and PAK2. RNA interference (RNAi)-mediated or pharmacological inhibition of PAKs using allosteric or adenosine triphosphate (ATP)-competitive compounds attenuated cell growth and increased apoptosis in vitro. Notably, PAK1- or PAK2-directed RNAi enhanced the antiproliferative effects of the type III RTK and protein kinase C inhibitor midostaurin. Treatment of FLT3- or PDGFRB-dependent ALLs with ATP-competitive PAK inhibitors markedly decreased catalytic activities of both PAK isoforms. In FLT3-driven ALL, this effect was augmented by coadministration of midostaurin resulting in synergistic effects on growth inhibition and apoptosis. Finally, combined treatment of FLT3 D835H PDX-ALL with the ATP-competitive group I PAK inhibitor FRAX486 and midostaurin in vivo significantly prolonged leukemia progression-free survival compared with midostaurin monotherapy or control. Our study establishes PAKs as potential downstream targets in RTK-dependent ALL of childhood, the inhibition of which might help prevent the selection or acquisition of resistance mutations toward tyrosine kinase inhibitors.
Project description:<p>Metabolic networks are interconnected and influence diverse cellular processes. The protein-metabolite interactions that mediate these networks are frequently low affinity and challenging to systematically discover. We developed mass spectrometry integrated with equilibrium dialysis for the discovery of allostery systematically (MIDAS) to identify such interactions. Analysis of 33 enzymes from human carbohydrate metabolism identified 830 protein-metabolite interactions, including known regulators, substrates and products as well as previously unreported interactions. We functionally validated a subset of interactions, including the isoform-specific inhibition of lactate dehydrogenase by long-chain acyl-coenzyme A. Cell treatment with fatty acids caused a loss of pyruvate-lactate interconversion dependent on lactate dehydrogenase isoform expression. These protein-metabolite interactions may contribute to the dynamic, tissue-specific metabolic flexibility that enables growth and survival in an ever-changing nutrient environment.</p>