Project description:Dysregulated oncogenic serine/threonine kinases play a pathological role in diverse forms of malignancies, including multiple myeloma (MM), and thus represent potential therapeutic targets. Here, we evaluated the biological and functional role of p21-activated kinase 4 (PAK4), and its potential as a new target in MM for clinical applications. PAK4 promoted MM cell growth and survival via activation of MM survival signaling pathways, including the MEK-ERK pathway. Furthermore, treatment with orally bioavailable PAK4 allosteric modulator (KPT-9274) significantly impacted MM cell growth and survival in a large panel of MM cell lines and primary MM cells alone and in the presence of bone marrow microenvironment. Intriguingly, we have identified FGFR3 as a novel binding partner of PAK4 and observed significant activity of KPT-9274 against t(4;14)-positive MM cells. These data support PAK4 as an oncogene in myeloma, and provide the rationale for the clinical evaluation of PAK4 modulator in myeloma.
Project description:Using multi-omic analyses, we identified PAK4 (P21 (RAC1) Activated Kinase 4) amplification and overexpression of Kinase PAK4 in a subset of bladder cancers. We confirmed the role of PAK4 in bladder cancer cell proliferation and invasion by in vitro experiments. Furthermore, our studies showed that PAK4 inhibitor is effective in curtailing bladder cancer cell growth. In order to understand the effect of PAK4 inhibition and knockdown on bladder cancer transcriptome, we performed RNA-sequencing of PAK4 siRNA transfected and PAK4 inhibitor (PF-3758309) treated bladder cancer cells (VM-CUB1). Analyses led to identification of direct targets of PAK4 in bladder cancer and associated pathways.
Project description:p21-activated kinase 4 (PAK4) is a serine/threonine kinase critical during development and with a proposed role in cancer and related cellular processes, including cell proliferation, survival and migration. However, while a limited number of PAK4-interacting proteins have been identified, the PAK4 interactome has not been systematically characterized. Here, we employed iTRAQ-based quantitative mass spectrometry of PAK4-immunioprecipitations from three distinct isolated cellular fractions to comprehensively profile the PAK4 interactome in human. These data will provide a valuable resource for further investigations on the role of PAK4 in physiology and disease.
Project description:Human PAK4 is an ubiquitously expressed p21-activated kinase which acts downstream of Cdc42. Since PAK4 is demonstrably enriched in cell-cell junctions, we probed the local protein environment around the kinase with a view to understanding its location and substrates. In U2OS cells expressing PAK4-BirA-GFP the resultant SILAC proximity analyses revealed a subset of 28 proteins that are primarily cell-cell junction components. The protein with highest relative biotin labelling was Afadin/AF6, which associates with the nectin family of homophilic junctional proteins. Reciprocally >50% of the PAK4-proximal proteins were identified by Afadin BioID. Pull-down experiments failed to identify junctional proteins, emphasizing the advantage of the BioID method. Mechanistically PAK4 depended on Afadin for its junctional localization, which is similar to the situation in Drosophila. A highly ranked PAK4-proximal protein LZTS2 was immuno-localized with Afadin at cell-cell junctions. Though PAK4 and Cdc42 are junctional, BioID analysis did not yield conventional cadherins, indicating their spatial segregation. To identify cellular PAK4 substrates we then assessed changes in phospho-proteome after 12 min PF-3758309 treatment. Among the PAK4-proximal junctional proteins 17 PAK4 sites were identified. Thus we show PAK4 is selective for the mammalian Afadin/nectin sub-compartment, with a demonstrably distinct localization from tight and cadherin junctions.
Project description:Mechanisms of constitutive NF-kappaB signaling in multiple myeloma are unknown. An inhibitor of IkappaB kinase beta (IKKbeta), targeting the classical NF-kappaB pathway, was lethal to many myeloma cell lines. Several had elevated expression of NIK due to genomic alterations or enhanced protein stability while others had inactivating mutations or deletion of TRAF3. Both abnormalities triggered the classical and alternative NF-kappaB pathways. A majority of primary myeloma patient samples and cell lines had elevated NF-kappaB target gene expression, often associated with genetic and epigenetic alteration of NIK, TRAF3, CYLD, BIRC2/BIRC3, CD40, NFKB1, and NFKB2. These genetic and functional data demonstrate that addiction to the NF-kappaB pathway is a frequent feature of myeloma and suggest that IKKbeta inhibitors hold promise for the treatment of this disease. Keywords: time series design
Project description:Mechanisms of constitutive NF-kappaB signaling in multiple myeloma are unknown. An inhibitor of IkappaB kinase beta (IKKbeta), targeting the classical NF-kappaB pathway, was lethal to many myeloma cell lines. Several had elevated expression of NIK due to genomic alterations or enhanced protein stability while others had inactivating mutations or deletion of TRAF3. Both abnormalities triggered the classical and alternative NF-kappaB pathways. A majority of primary myeloma patient samples and cell lines had elevated NF-kappaB target gene expression, often associated with genetic and epigenetic alteration of NIK, TRAF3, CYLD, BIRC2/BIRC3, CD40, NFKB1, and NFKB2. These genetic and functional data demonstrate that addiction to the NF-kappaB pathway is a frequent feature of myeloma and suggest that IKKbeta inhibitors hold promise for the treatment of this disease. Keywords: time series design
Project description:Spermatogenesis is a complex cell differentiation process that includes marked genetic, cellular functional and structural changes. It requires tight regulation, since disturbances in any of the spermatogenic stages would lead to fertility deficiencies. In order to increase our knowledge of signal transduction during sperm development, we carried out a large-scale identification of the phosphorylation events that occur in the human gonad. Metal oxide affinity chromatography using TiOx combined with LC-MS/MS was conducted to profile the phosphoproteome of human testes with full spermatogenesis. A total of 8187 phosphopeptides derived from 2661 proteins were identified, resulting in the most complete report of human testicular phosphoproteins to date. Phosphorylation events were enriched in proteins functionally related to spermatogenesis, as well as to highly active processes in the male gonad, such as transcriptional and translational regulation, cytoskeleton organization, DNA packaging, cell cycle and apoptosis. Moreover, 174 phosphorylated kinases were identified. The most active and abundant human protein kinases in the testis were predicted both by the phosphorylation status of the kinase activation loop and the number of phosphopeptide spectra identified. The potential function of two of those kinases, cyclin-dependent kinase 12 (CDK12) and p21-activated kinase 4(PAK4), has been explored by protein-protein interaction analysis, immunodetection in human and mouse testicular tissue, and functional assay in a human embryonal carcinoma cell line. The co-localization of CDK12 with Golgi markers and probably pro-acrosomal vesicles suggests a potential crucial role of this protein kinase in sperm formation. PAK4 expression has been found limited to human spermatogonia, and a role in embryonal carcinoma cell response to apoptosis has been observed. Together, our data confirm that phosphoregulation by protein kinases is highly active in sperm differentiation, and open a window to detailed characterization and validation of potential targets for the development of drugs modulating male fertility, and tumor behavior.
Project description:Although substantial progress has been made in the treatment of B-cell acute lymphoblastic leukemia (B-ALL), the prognosis of patients with refractory or relapsed B-ALL remains dismal. Novel therapeutic strategies are needed to improve the outcome of these patients. KPT-9274 is a novel dual inhibitor of p21-activated kinase 4 (PAK4) and nicotinamide phosphoribosyltransferase (NAMPT). PAK4 is a serine/threonine kinases and it regulates a variety of protein kinases involved in cell survival, motility and proliferation. NAMPT is a rate-limiting enzyme in the salvage biosynthesis pathway of nicotinamide adenine dinucleotide (NAD), which plays a vital role in energy metabolism. Here, we show that KPT-9274 strongly inhibits B-ALL cell growth regardless of cytogenetic abnormalities. We also demonstrate the potent in vivo efficacy and tolerability of KPT-9274 in orthotopic xenograft murine models using patient-derived BALL cells. Although KPT-9274 affected both PAK4 signaling pathways and NAD+ dependent pathways, B-ALL cell growth inhibition mediated by KPT-9274 was largely abolished by nicotinic acid supplementation, indicating that the inhibitory effect of KPT- 9274 on B-ALL cell growth was mainly exerted by NAD+ depletion through blockade of NAMPT enzyme activity. Moreover, we found that B-ALL cells were especially vulnerable to NAD+ depletion, and the susceptibility to treatment with KPT-9274 was related to the reduced NAD+ reserve in B-ALL cells. NAD+ depletion may be a promising alternative approach to treating patients with B-ALL.
Project description:Resistance to proteasome inhibitors (PIs) is a ubiquitous clinical concern in multiple myeloma. We proposed that signaling-level responses after PI would reveal new means to enhance efficacy. Unbiased phosphoproteomics after the PI carfilzomib surprisingly demonstrated the most prominent phosphorylation changes on spliceosome components. Spliceosome modulation was invisible to RNA or protein abundance alone. Transcriptome analysis demonstrated broad-scale intron retention suggestive of PI-specific splicing interference. Direct spliceosome inhibition synergized with carfilzomib and showed potent anti-myeloma activity. Functional genomics and exome sequencing further supported the spliceosome as a specific vulnerability in myeloma. Our results propose splicing interference as an unrecognized modality of PI mechanism, reveal additional modes of spliceosome modulation, and suggest spliceosome targeting as a promising therapeutic strategy in myeloma.