The Experts below are selected from a list of 111999 Experts worldwide ranked by ideXlab platform
Gary M Bokoch - One of the best experts on this subject based on the ideXlab platform.
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Pak1 regulates focal adhesion strength, myosin IIA distribution, and actin dynamics to optimize cell migration
Journal of Cell Biology, 2011Co-Authors: Violaine D. Delorme-walker, Clare M Waterman, Jonathan Chernoff, Jeffrey R. Peterson, Gaudenz Danuser, Celine Dermardirossian, Gary M BokochAbstract:Cell motility requires the spatial and temporal coordination of forces in the actomyosin cytoskeleton with extracellular adhesion. The biochemical mechanism that coordinates filamentous actin (F-actin) assembly, myosin contractility, adhesion dynamics, and motility to maintain the balance between adhesion and contraction remains unknown. In this paper, we show that P21-Activated Kinases (Paks), downstream effectors of the small guanosine triphosphatases Rac and Cdc42, biochemically couple leading-edge actin dynamics to focal adhesion (FA) dynamics. Quantitative live cell microscopy assays revealed that the inhibition of Paks abolished F-actin flow in the lamella, displaced myosin IIA from the cell edge, and decreased FA turnover. We show that, by controlling the dynamics of these three systems, Paks regulate the protrusive activity and migration of epithelial cells. Furthermore, we found that expressing Pak1 was sufficient to overcome the inhibitory effects of excess adhesion strength on cell motility. These findings establish Paks as critical molecules coordinating cytoskeletal systems for efficient cell migration.
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regulation of microtubule destabilizing activity of op18 stathmin downstream of rac1
Journal of Biological Chemistry, 2004Co-Authors: Torsten Wittmann, Gary M Bokoch, Clare M WatermanstorerAbstract:Abstract In the leading edge of migrating cells, a subset of microtubules exhibits net growth in a Rac1- and P21-Activated kinase-dependent manner. Here, we explore the possibility of whether phosphorylation and inactivation of the microtubule-destabilizing protein Op18/stathmin could be a mechanism regulating microtubule dynamics downstream of Rac1 and P21-Activated Kinases. We find that, in vitro, Pak1 phosphorylates Op18/stathmin specifically at serine 16 and inactivates its catastrophe promoting activity in biochemical and time lapse microscopy microtubule assembly assays. Furthermore, phosphorylation of either serine 16 or 63 is sufficient to inhibit Op18/stathmin in vitro. In cells, the microtubule-destabilizing effect of an excess of Op18/stathmin can be partially overcome by expression of constitutively active Rac1(Q61L), which is dependent on Pak activity, suggesting that the microtubule cytoskeleton can be regulated through inactivation of Op18/stathmin downstream of Rac1 and Pak in vivo. However, in vivo, Pak1 activity alone is not sufficient to phosphorylate Op18, indicating that additional pathways downstream of Rac1 are required for Op18 regulation.
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regulation of leading edge microtubule and actin dynamics downstream of rac1
Journal of Cell Biology, 2003Co-Authors: Torsten Wittmann, Gary M Bokoch, Clare M WatermanstorerAbstract:Actin in migrating cells is regulated by Rho GTPases. However, Rho proteins might also affect microtubules (MTs). Here, we used time-lapse microscopy of PtK1 cells to examine MT regulation downstream of Rac1. In these cells, “pioneer” MTs growing into leading-edge protrusions exhibited a decreased catastrophe frequency and an increased time in growth as compared with MTs further from the leading edge. Constitutively active Rac1(Q61L) promoted pioneer behavior in most MTs, whereas dominant-negative Rac1(T17N) eliminated pioneer MTs, indicating that Rac1 is a regulator of MT dynamics in vivo. Rac1(Q61L) also enhanced MT turnover through stimulation of MT retrograde flow and breakage. Inhibition of P21-Activated Kinases (Paks), downstream effectors of Rac1, inhibited Rac1(Q61L)-induced MT growth and retrograde flow. In addition, Rac1(Q61L) promoted lamellipodial actin polymerization and Pak-dependent retrograde flow. Together, these results indicate coordinated regulation of the two cytoskeletal systems in the leading edge of migrating cells.
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Biology of the P21-Activated Kinases
Annual review of biochemistry, 2003Co-Authors: Gary M BokochAbstract:The P21-Activated Kinases (PAKs) 1-3 are serine/threonine protein Kinases whose activity is stimulated by the binding of active Rac and Cdc42 GTPases. Our understanding of the regulation and biology of these important signaling proteins has increased tremendously since their discovery in the mid-1990s. PAKs 1-3 are activated by a variety of GTPase-dependent and -independent mechanisms. This complexity reflects the contributions of PAK function in many cellular signaling pathways and the need to carefully control PAK action in a highly localized manner. PAKs serve as important regulators of cytoskeletal dynamics and cell motility, transcription through MAP kinase cascades, death and survival signaling, and cell-cycle progression. Consequently, PAKs have also been implicated in a number of pathological conditions and in cell transformation. We propose here a key role for PAK action in coordinating the dynamics of the actin and microtubule cytoskeletons during directional motility of cells, as well as in other functions requiring cytoskeletal polarization.
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Regulation of Macropinocytosis by P21-Activated Kinase-1
Molecular biology of the cell, 2000Co-Authors: Suranganie Dharmawardhane, Jonathan Chernoff, Mary Ann Sells, Annette Schürmann, Sandra L. Schmid, Gary M BokochAbstract:The process of macropinocytosis is an essential aspect of normal cell function, contributing to both growth and motile processes of cells. P21-Activated Kinases (PAKs) are targets for activated Rac and Cdc42 guanosine 5′-triphosphatases and have been shown to regulate the actin-myosin cytoskeleton. In fibroblasts PAK1 localizes to areas of membrane ruffling, as well as to amiloride-sensitive pinocytic vesicles. Expression of a PAK1 kinase autoinhibitory domain blocked both platelet-derived growth factor- and RacQ61L-stimulated uptake of 70-kDa dextran particles, whereas an inactive version of this domain did not, indicating that PAK kinase activity is required for normal growth factor-induced macropinocytosis. The mechanisms by which PAK modulate macropinocytosis were examined in NIH3T3 cell lines expressing various PAK1 constructs under the control of a tetracycline-responsive transactivator. Cells expressing PAK1 (H83,86L), a mutant that dramatically stimulates formation of dorsal membrane ruffles, exhibited increased macropinocytic uptake of 70-kDa dextran particles in the absence of additional stimulation. This effect was not antagonized by coexpression of dominant-negative Rac1-T17N. In the presence of platelet-derived growth factor, both PAK1 (H83,86L) and a highly kinase active PAK1 (T423E) mutant dramatically enhanced the uptake of 70-kDa dextran. Neither wild-type PAK1 nor vector controls exhibited enhanced macropinocytosis, nor did PAK1 (H83,86L) affect clathrin-dependent endocytic mechanisms. Active versions of PAK1 enhanced both growth factor-stimulated 70-kDa dextran uptake and efflux, suggesting that PAK1 activity modulated pinocytic vesicle cycling. These data indicate that PAK1 plays an important regulatory role in the process of macropinocytosis, perhaps related to the requirement for PAK in directed cell motility.
Jonathan Chernoff - One of the best experts on this subject based on the ideXlab platform.
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targeting group i p21 activated Kinases to control malignant peripheral nerve sheath tumor growth and metastasis
Oncogene, 2017Co-Authors: Galina Semenova, Dina Stepanova, Cara Dubyk, E Handorf, S M Deyev, Alexander J Lazar, Jonathan ChernoffAbstract:Malignant peripheral nerve sheath tumors (MPNSTs) are devastating sarcomas for which no effective medical therapies are available. Over 50% of MPSNTs are associated with mutations in NF1 tumor suppressor gene, resulting in activation of Ras and its effectors, including the Raf/Mek/Erk and PI3K/Akt/mTORC1 signaling cascades, and also the WNT/β-catenin pathway. As Group I P21-Activated Kinases (Group I Paks, PAK1/2/3) have been shown to modulate Ras-driven oncogenesis, we asked if these enzymes might regulate signaling in MPNSTs. In this study we found a strong positive correlation between the activity of PAK1/2/3 and the stage of human MPNSTs. We determined that reducing Group I Pak activity diminished MPNST cell proliferation and motility, and that these effects were not accompanied by significant blockade of the Raf/Mek/Erk pathway, but rather by reductions in Akt and β-catenin activity. Using the small molecule PAK1/2/3 inhibitor Frax1036 and the MEK1/2 inhibitor PD0325901, we showed that the combination of these two agents synergistically inhibited MPNST cell growth in vitro and dramatically decreased local and metastatic MPNST growth in animal models. Taken together, these data provide new insights into MPNST signaling deregulation and suggest that co-targeting of PAK1/2/3 and MEK1/2 may be effective in the treatment of patients with MPNSTs.
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kinase activity of pak2 an effector of rac cdc42 and its interaction with β pix is required for murine hematopoietic stem cell shape f actin formation directional migration in vitro and for hspc homing to bone marrow in vivo
Blood, 2013Co-Authors: Pavankumar N G Reddy, Jonathan Chernoff, Rachelle Kosoff, Maria Radu, Jenna Wood, Chad E Harris, Meaghan Mcguinness, David A WilliamsAbstract:Hematopoietic stem and progenitor cell (HSPC) migration, marrow homing and engraftment are key physiological processes regulating hematopoiesis post transplantation. These processes are the result of the orchestrated actions of multiple extracellular stimuli, which regulate actin remodeling, cell polarity, chemotaxis and cell-cell interactions. In HSPC, the Rho GTPases Rac and CDC42 act as molecular switches that integrate extracellular stimuli in a spatially regulated manner to control cell migration and mediate homing to marrow and mobilization as well as cell survival/ proliferation pathways to mediate engraftment (Gu et al., Science 2003; Cancelas et al., Nature Medicine 2005; Wang et al., Blood 2006) . Using an inhibitory peptide against Group A p21 activated Kinases (Pak1-3), key effectors of Rac/ CDC42 and individual Pak1 & 2 genetic knock-out mice, we recently demonstrated that Pak Kinases, specifically Pak2, are important for HSPC homing and engraftment ( Dorrance et al., Blood 2013 ). Pak2 is a multi-domain protein that contains a C-terminal kinase domain and multiple N-terminal protein-interaction domains. Among these is a non-classical SH3-binding site for the guanine-nucleotide-exchange factor β-PIX, which was shown to be critical for both activation of Rac1 and its localization to and induction of membrane ruffles ( Klooster et al., Journal of Cell Biology 2006 ). In this study we further explored the role of these domains of Pak2 in key HSPC functions, including homing to bone marrow in vivo . We employed a multi-cistronic retrovirus vector that simultaneously deleted floxed endogenous Pak2 gene sequences and rescued with either wild type (WT), a kinase dead (KD) mutant (K278A, defective in auto/ trans phosphorylation) or a Δβ-PIX mutant, (P185/R186A, that cannot bind to β-PIX). As previously demonstrated deletion of Pak2 (Pak2 Δ/Δ) was associated with abnormal SDF-1 stimulated cell protrusions containing F-actin (as demonstrated by confocal and electron microscopy) and these HSPC displayed decreased directional migration (Euclidean distance in Pak2Δ/Δ vs. Pak2WT/WT: 39.6µm ±9.6 vs. 96.6µm ±21.6; P<0.05). This phenotype of abnormal cell protrusions and decreased directional migration was rescued by expressing Pak2-WT (Pak2WT/WT vs. Pak2-WT: 96.6µm ±21.6 vs. 74.0µm ±18.7; P: not significant) but not by expressing Pak2-KD (Pak2WT/WT vs. Pak2-KD: 96.6µm ±21.6 vs. 33.6µm ±6.3; P<0.05) demonstrating the requirement of Pak2 kinase activity in SDF1-induced cell polarization and directed cell migration. Interestingly, we found abnormal F-actin clustering associated with defective polarization (by confocal microscopy) and decreased velocity of cell migration in time-lapsed video microscopy when Pak2-deletion was rescued with Pak2-Δβ-PIX (velocity of migration Pak2WT/WT vs. Pak2-Δβ-PIX, 0.32µm/minute ±0.02 vs. 0.13µm/minute ±0.02; P<0.001), indicating the requirement of β-PIX exchange factor interaction with Pak2 in directed migration. To test whether these in vitro phenotypes were associated with changes in homing efficiency to bone marrow, we performed in vivo homing assays of rescued HSPC. Transduced, GFP-sorted Lin-Sca1+Kit+ cells of each genotype were injected into lethally-irradiated C57BL/6 recipient mice (N= 12-29 /genotype). Twelve hours post-transplantation the number of EGFP+ cells in the bone marrow was determined and percent homing is calculated. Compared to Pak2 WT/WT, Pak2Δ/Δ HSPC displayed reduced homing (99.26%± 4.9 vs. 53.4% ± 4.2; P< 0.0001). The homing defect was rescued by Pak2-WT (Pak2WT/WT vs. Pak2-WT rescue: 99.26%± 4.9 vs. 86% ± 8.5; P: not significant). However neither Pak2-KD nor Pak2-Δβ-PIX rescued in vivo homing: 99.26% ±4.9 vs. 38.9% ±3.7 vs. 33.0%± 6.0; P< 0.0001 each mutant vs.Pak2WT/WT) proving the necessity of kinase activity and interaction with β-PIX for bone marrow homing. Taken together we show that both Pak2-kinase activity and its interaction with β-PIX exchange factor are required for coordinated HSPC F-actin formation and cell polarization, directed cell migration in vitro and homing to bone marrow in vivo . These data directly link the in vitro effects of Pak2 kinase with in vivo bone marrow homing. Note All p values are calculated by Mann Whitney test. Disclosures: No relevant conflicts of interest to declare.
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frax597 a small molecule inhibitor of the p21 activated Kinases inhibits tumorigenesis of neurofibromatosis type 2 nf2 associated schwannomas
Journal of Biological Chemistry, 2013Co-Authors: Silvia Licciulli, Jonathan Chernoff, Jasna Maksimoska, Chun Zhou, Scott Troutman, Smitha Kota, Qin Liu, Sergio G Duron, David A Campbell, Jeffrey FieldAbstract:The P21-Activated Kinases (PAKs) are immediate downstream effectors of the Rac/Cdc42 small G-proteins and implicated in promoting tumorigenesis in various types of cancer including breast and lung carcinomas. Recent studies have established a requirement for the PAKs in the pathogenesis of Neurofibromatosis type 2 (NF2), a dominantly inherited cancer disorder caused by mutations at the NF2 gene locus. Merlin, the protein product of the NF2 gene, has been shown to negatively regulate signaling through the PAKs and the tumor suppressive functions of Merlin are mediated, at least in part, through inhibition of the PAKs. Knockdown of PAK1 and PAK2 expression, through RNAi-based approaches, impairs the proliferation of NF2-null schwannoma cells in culture and inhibits their ability to form tumors in vivo. These data implicate the PAKs as potential therapeutic targets. High-throughput screening of a library of small molecules combined with a structure-activity relationship approach resulted in the identification of FRAX597, a small-molecule pyridopyrimidinone, as a potent inhibitor of the group I PAKs. Crystallographic characterization of the FRAX597/PAK1 complex identifies a phenyl ring that traverses the gatekeeper residue and positions the thiazole in the back cavity of the ATP binding site, a site rarely targeted by kinase inhibitors. FRAX597 inhibits the proliferation of NF2-deficient schwannoma cells in culture and displayed potent anti-tumor activity in vivo, impairing schwannoma development in an orthotopic model of NF2. These studies identify a novel class of orally available ATP-competitive Group I PAK inhibitors with significant potential for the treatment of NF2 and other cancers.
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group i p21 activated Kinases paks promote tumor cell proliferation and survival through the akt1 and raf mapk pathways
Molecular Cancer Research, 2012Co-Authors: Craig W Menges, Jonathan Chernoff, Jeffrey R. Peterson, Eleonora Sementino, Jacqueline Talarchek, Joseph R TestaAbstract:Group I P21-Activated Kinases (PAKs) are important effectors of the small GTPases Rac and Cdc42, which regulate cell motility/migration, survival, proliferation and gene transcription. Hyperactivation of these Kinases have been reported in many tumor types, making PAKs attractive targets for therapeutic intervention. PAKs are activated by growth factor-mediated signaling and are negatively regulated by the tumor suppressor NF2/Merlin. Thus, tumors characterized by NF2 inactivation would be expected to show hyperactivated PAK signaling. Based on this rationale, we evaluated the status of PAK signaling in malignant mesothelioma (MM), an aggressive neoplasm that is resistant to current therapies and shows frequent inactivation of NF2. We demonstrate that group I PAKs are activated in most MMs and MM cell lines and that genetic or pharmacological inhibition of PAKs is sufficient to inhibit MM cell proliferation and survival. We also identify downstream effectors and signaling pathways that may contribute mechanistically to PAK-related tumorigenesis. Specifically, we show that inhibition of PAK results in attenuation of AKT and Raf-MAPK signaling and decreased tumor cell viability. Collectively, these data suggest that pharmacological inhibition of group I PAKs may have therapeutic efficacy in tumors characterized by PAK activation.
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Pak1 regulates focal adhesion strength, myosin IIA distribution, and actin dynamics to optimize cell migration
Journal of Cell Biology, 2011Co-Authors: Violaine D. Delorme-walker, Clare M Waterman, Jonathan Chernoff, Jeffrey R. Peterson, Gaudenz Danuser, Celine Dermardirossian, Gary M BokochAbstract:Cell motility requires the spatial and temporal coordination of forces in the actomyosin cytoskeleton with extracellular adhesion. The biochemical mechanism that coordinates filamentous actin (F-actin) assembly, myosin contractility, adhesion dynamics, and motility to maintain the balance between adhesion and contraction remains unknown. In this paper, we show that P21-Activated Kinases (Paks), downstream effectors of the small guanosine triphosphatases Rac and Cdc42, biochemically couple leading-edge actin dynamics to focal adhesion (FA) dynamics. Quantitative live cell microscopy assays revealed that the inhibition of Paks abolished F-actin flow in the lamella, displaced myosin IIA from the cell edge, and decreased FA turnover. We show that, by controlling the dynamics of these three systems, Paks regulate the protrusive activity and migration of epithelial cells. Furthermore, we found that expressing Pak1 was sufficient to overcome the inhibitory effects of excess adhesion strength on cell motility. These findings establish Paks as critical molecules coordinating cytoskeletal systems for efficient cell migration.
Audrey Minden - One of the best experts on this subject based on the ideXlab platform.
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P21 Activated Kinase Signaling in Cancer
Seminars in cancer biology, 2018Co-Authors: Chetan K. Rane, Audrey MindenAbstract:The p21 Activated Kinases (PAKs) are a family of serine threonine Kinases, that consist of 6 members, PAKs 1-6, which are positioned at an intersection of multiple signaling pathways implicated in oncogenesis. The PAKs were originally identified as protein Kinases that function downstream of the Ras related Rho GTPases Cdc42 and Rac. PAK1 and PAK4, which belong to Group I and Group II PAKs, respectively, are most often associated with tumorigenesis. On account of their well characterized roles in cancer, several small molecule inhibitors are being developed to inhibit the PAKs, and there is interest in investigating their efficacy as either first line or adjuvant treatments for cancer. Studies to delineate PAK regulated signaling pathways as well as the long term effects of PAK overexpression on gene expression are beginning to shed light on the mechanism by which PAK proteins may lead to cancer when they are overexpressed or activated. This review will describe the association between PAK expression in cancer, with a focus on PAK1 and PAK4, which are most often associated with the disease. The current understanding of the molecular mechanisms by which the PAKs operate in cancer will be discussed. We will also review some of the potential drug candidates, and discuss which of them are currently being tested for their efficacy in cancer treatments.
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abstract 1864 in vivoefficacy of the pak4 allosteric modulator kpt 9274 against a triple negative breast cancer model
Cancer Research, 2016Co-Authors: Chetan K. Rane, William Senapedis, Erkan Baloglu, Sharon Shacham, Audrey MindenAbstract:The P21-Activated Kinases (PAK) belong to a family of serine threonine Kinases that promote cell survival and play an important role in cell proliferation, cell cycle regulation and cell shape determination. There are six mammalian PAK proteins which can be subdivided into two groups by sequence homology and mode of activation- Group A PAKs consisting of PAK 1, 2 and 3 and Group B PAKs consisting of PAK 4, 5 and 6. We have found that PAK4 protein levels are elevated in breast cancer, including Her2 positive and triple negative breast cancers, while it is expressed at low levels in normal mammary tissue, making it an attractive drug target. PAK inhibitors are being tested for effectiveness against solid tumors, but generation of highly specific PAK4 inhibitors has been a challenge. Furthermore, PAK4 has been reported to have kinase-independent functions. Therefore inhibiting its kinase activity alone might not be sufficient in blocking its tumorigenic potential. Our lab has previously reported the effectiveness of PAK4 allosteric modulators (PAM; KPT-8752 and KPT-9274) against multiple breast cancer cell lines. These novel PAK4 inhibitors reduce steady state protein levels and were able to block cell growth, cell migration and induce apoptosis in breast cancer cell lines, without affecting the control cells. Here, we tested the efficacy of the orally bioavailable PAM, KPT-9274 against tumors formed by the triple negative breast cancer cell line, MDA-MB-231. Following six weeks of treatment with orally administered KPT-9274 (150mg/kg bidx4), there was almost a five-fold reduction in tumor volume and tumor weight in the treatment group as compared to the control group. The treatment did not significantly affect mice body weight. After six weeks of treatment, the tumors were excised and analyzed for PAK4 levels. We observed a significant decrease in PAK4 levels in excised tumors from the treatment group as compared to those from the control group. PAK1 levels were monitored to see any off-target effects, but their levels were unchanged. Our results indicate that PAK4 plays a key functional role in triple negative breast cancer and treatment with an orally administered KPT-9274 was capable of specifically binding and inhibiting PAK4, and consequently reducing tumor growth. Future studies analyzing the effects of KPT-9274 in blocking PAK4 mediated functions that promote tumorigenesis are ongoing. Additional studies of the effectiveness of KPT-9274 on mammary fat pad tumors formed by MDA-MB-231 and the ER positive cell line, MCF7 are under investigation. Citation Format: Chetan Rane, William Senapedis, Erkan Baloglu, Sharon Shacham, Audrey G. Minden. In vivo efficacy of the PAK4 allosteric modulator KPT-9274 against a triple-negative breast cancer model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1864.
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pak4 6 in cancer and neuronal development
Cellular logistics, 2012Co-Authors: Audrey MindenAbstract:PAKs 4, 5 and 6 are members of the group B family of P21-Activated Kinases. Among this group, PAK4 has been most extensively studied. While it has essential roles in embryonic development, in adults high levels of PAK4 are frequently associated with cancer. PAK4 is overexpressed in a variety of cancers, and the Pak4 gene is amplified in some cancers. PAK4 overexpression is sufficient to cause oncogenic transformation in cells and in mouse models. The tight connection between PAK4 and cancer make it a promising diagnostic tool as well as a potential drug target. The group B PAKs also have important developmental functions. PAK4 is important for many early developmental processes, while PAK5 and PAK6 play roles in learning and memory in mice. This chapter provides an overview of the roles of the group B PAKs in cancer as well as development, and includes a discussion of PAK mediated signaling pathways and cellular functions.
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PAK4 Functions in Tumor Necrosis Factor (TNF) α-induced Survival Pathways by Facilitating TRADD Binding to the TNF Receptor
The Journal of biological chemistry, 2005Co-Authors: Audrey MindenAbstract:Abstract PAK4 is a member of the group B family of P21-Activated Kinases. Its expression is elevated in many cancer cell lines, and activated PAK4 is highly transforming, suggesting that it plays an important role in tumorigenesis. Although most previous work was carried out with overexpressed PAK4, here we used RNA interference to knock down endogenous PAK4 in cancer cells. By studying PAK4 knockdown HeLa cells, we demonstrated that endogenous PAK4 is required for anchorage-independent growth. Because cell survival is a key part of tumorigenesis and anchorage-independent growth, we studied whether PAK4 has a role in protecting cells from cell death. To address this, we studied the role for PAK4 downstream to the tumor necrosis factor (TNF) α receptor. Although overexpressed PAK4 was previously shown to abrogate proapoptotic pathways, here we demonstrate that endogenous PAK4 is required for the full activation of prosurvival pathways induced by TNFα. Our results indicate that PAK4 is required for optimal binding of the scaffold protein TRADD to the activated TNFα receptor through both kinase-dependent and kinase-independent mechanisms. Consequently, activation of several prosurvival pathways, including the NFκB and ERK pathways, is reduced in the absence of PAK4. Interestingly, constitutive activation of the NFκB and ERK pathways could compensate for the lack of PAK4, indicating that these pathways function downstream to PAK4. The role for PAK4 in regulating prosurvival pathways is a completely new function for this protein, and the connection between PAK4 and cell survival under stress helps explain its role in tumorigenesis and development.
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PAK4 Functions in Tumor Necrosis Factor (TNF) -induced Survival Pathways by Facilitating TRADD Binding to the
2005Co-Authors: Audrey MindenAbstract:PAK4 is a member of the group B family of P21-Activated Kinases. Its expression is elevated in many cancer cell lines, and activated PAK4 is highly transforming, suggesting that it plays an important role in tumorigenesis. Although most previous work was carried out with overexpressed PAK4, here we used RNA interference to knock down endogenous PAK4 in cancer cells. By studying PAK4 knockdown HeLa cells, we demonstrated that endogenous PAK4 is required for anchorage-independent growth. Because cell survival is a key part of tumorigenesis and anchorage-independent growth, we studied whether PAK4 has a role in protecting cells from cell death. To address this, we studied the role for PAK4 downstream to the tumor necrosis factor (TNF) receptor. Although overexpressed PAK4 was previously shown to abrogate proapoptotic pathways, here we demonstrate that endogenous PAK4 is required for the full activation of prosurvival pathways induced by TNF .O ur results indicate that PAK4 is required for optimal binding of the scaffold protein TRADD to the activated TNF receptor through both kinase-dependent and kinase-independent mechanisms. Consequently, activation of several prosurvival pathways, including the NFB and ERK pathways, is reduced in the absence of PAK4. Interestingly, constitutive activation of the NFB and ERK pathways could compensate for the lack of PAK4, indicating that these pathways function downstream to PAK4. The role for PAK4 in regulating prosurvival pathways is a completely new function for this protein, and the connection between PAK4 and cell survival under stress helps explain its role in tumorigenesis and development. Tumor necrosis factor (TNF) 2 was originally discovered as an anticancer cytokine that can induce apoptosis in certain tumor cells (1).
Mehrdad Nikfarjam - One of the best experts on this subject based on the ideXlab platform.
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p21 activated kinase signalling in pancreatic cancer new insights into tumour biology and immune modulation
World Journal of Gastroenterology, 2018Co-Authors: Kai Wang, Graham S Baldwin, Mehrdad NikfarjamAbstract:Pancreatic cancer is one of the most aggressive and lethal malignancies worldwide, with a very poor prognosis and a five-year survival rate less than 8%. This dismal outcome is largely due to delayed diagnosis, early distant dissemination and resistance to conventional chemo-therapies. Kras mutation is a well-defined hallmark of pancreatic cancer, with over 95% of cases harbouring Kras mutations that give rise to constitutively active forms of Kras. As important down-stream effectors of Kras, P21-Activated Kinases (PAKs) are involved in regulating cell proliferation, apoptosis, invasion/migration and chemo-resistance. Immunotherapy is now emerging as a promising treatment modality in the era of personalized anti-cancer therapeutics. In this review, basic knowledge of PAK structure and regulation is briefly summarised and the pivotal role of PAKs in Kras-driven pancreatic cancer is highlighted in terms of tumour biology and chemo-resistance. Finally, the involvement of PAKs in immune modulation in the tumour microenvironment is discussed and the potential advantages of targeting PAKs are explored.
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inhibition of group 1 p21 activated Kinases suppresses pancreatic stellate cell activation and increases survival of mice with pancreatic cancer
International Journal of Cancer, 2017Co-Authors: Dannel Yeo, Phoebe A Phillips, Graham S Baldwin, Mehrdad NikfarjamAbstract:Pancreatic cancer remains one of the most lethal of all solid tumors. Pancreatic stellate cells (PSCs) are primarily responsible for the fibrosis that constitutes the stroma and P21-Activated kinase 1 (PAK1) may have a role in signalling pathways involving PSCs. This study aimed to examine the role of PAK1 in PSCs and in the interaction of PSCs with pancreatic cancer cells. Human PSCs were isolated using the modified outgrowth method. The effect of inhibiting PAK1 with group 1 PAK inhibitor, FRAX597, on cell proliferation and apoptosis in vitro was measured by thymidine incorporation and annexin V assays, respectively. The effect of depleting host PAK1 on the survival of mice with pancreatic Pan02 cell tumors was evaluated using PAK1 knockout (KO) mice. PAK1 was expressed in isolated PSCs. FRAX597 reduced the activation of PSCs, inhibited PSC proliferation, and increased PSC apoptosis at least in partial by inhibiting PAK1 activity. The decreased expression and activity of PAK1 in PAK1 KO mice tumors was associated with an increased mouse survival. These results implicate PAK1 as a regulator of PSC activation, proliferation and apoptosis. Targeting stromal PAK1 could increase therapeutic response and survival of patients with pancreatic cancer.
Richard A. Cerione - One of the best experts on this subject based on the ideXlab platform.
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regulation of the cool pix proteins key binding partners of the cdc42 rac targets the p21 activated Kinases
Journal of Biological Chemistry, 2002Co-Authors: Qiyu Feng, Richard A. Cerione, John G. Albeck, Wannian YangAbstract:Abstract The Cool (cloned-outof library)/Pix (forPAK-interactive exchange factor) proteins directly bind to members of the PAK family of serine/threonine Kinases and regulate their activity. Three members of the Cool/Pix family have shown distinct regulatory activities: (i) p50Cool-1 inhibits Cdc42/Rac-stimulated PAK activity, (ii) p85Cool-1/β-Pix has a permissive effect on Cdc42/Rac-stimulated activity, and (iii) p90Cool-2/α-Pix strongly activates PAK. We initially suspected that these different functional effects were due to a binding interaction that occurs at the carboxyl-terminal ends of the larger Cool/Pix proteins, thus enabling them to stimulate (or at least permit) rather than inhibit PAK activity. This led to the identification of the Cat proteins (forCool-associated tyrosine phosphosubstrates). However, here we show that the Cat proteins bind to the carboxyl-terminal ends of p85Cool-1(residues 523–546) and Cool-2 (residues 647–670), and that the binding of Cat to Cool-2 in fact is not necessary for the Cool-2-mediated activation of PAK. Rather, an 18-amino acid region, designated T1, that is present in the Cool-1 proteins, but missing in Cool-2, is essential for controlling the regulation of PAK activity by Cool-1/β-Pix in vivo. Deletion of T1 yielded a p85Cool-1 molecule that mimicked the Cool-2 protein and was capable of strongly stimulating PAK activity. However, when T1 was added to Cool-2, the ability of Cool-2 to directly activate PAK was lost. We conclude that T1 represents a novel regulatory domain that accounts for the specific functional effects on PAK activity exhibited by the different members of the Cool/Pix family.
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A Novel Regulator of P21-Activated Kinases
The Journal of biological chemistry, 1998Co-Authors: Shubha Bagrodia, Stephen J Taylor, K. Antonia Jordon, Linda Van Aelst, Richard A. CerioneAbstract:Abstract Proteins of the P21-Activated kinase (Pak) family have been implicated in the regulation of gene expression, cytoskeletal architecture, and apoptosis. Although the ability of Cdc42 and Rac GTPases to activate Pak is well established, relatively little else is known about Pak regulation or the identity of Pak cellular targets. Here we report the identification of two closely related Pak3-binding proteins, possibly arising from alternative splicing, designated p50 and p85Cool-1 (cloned outof library). Both isoforms of Cool contain a Src homology 3 domain that directly mediates interaction with Pak3 and tandem Dbl homology and pleckstrin homology domains. Despite the presence of the Dbl homology-pleckstrin homology motif, a characteristic of Rho family activators, activation of Cdc42 or Rac by Cool is not detectable. Instead binding of p50Cool-1, but not p85Cool-1, to Pak3 represses its activation by upstream activators such as the Dbl oncoprotein, indicating a novel mechanism of regulation of Pak signaling.
