Biomedical subjects

Matthias Gaestel

Publications and source records attributed to Matthias Gaestel.

At least 19 recordsLinked to original sources

PubMed2007

Smooth muscle alpha-actin expression and myofibroblast differentiation by TGFbeta are dependent upon MK2.

Fibroblasts play a major role in processes such as wound repair, scarring, and fibrosis. Differentiation into myofibroblasts, characterized by upregulation of smooth muscle alpha-actin (smalpha) in response to profibrotic agents such as TGFbeta is believed to be an important step in fibrosis. Therefore, elucidating mechanisms of myofibroblast differentiation might reveal novel targets in treating diseases such as idiopathic pulmonary fibrosis (IPF). MK2 is a kinase substrate of p38 MAP kinase that mediates some effects of p38 activation on the actin cytoskeleton. Using mouse embryonic fibroblasts (MEF) from MK2 knockout (MK2(-/-)) mice, we demonstrate that disrupting expression of MK2 expression reduces filamentous actin and stress fibers. It also causes MK2(-/-) MEF to express less smalpha than their corresponding wild-type (WT) MEF at baseline and in response to TGFbeta. Furthermore, TGFbeta causes downregulation of smalpha in MK2(-/-) MEF, instead of upregulation observed in WT MEF. Expression of other fibroblast markers, such as collagen, is not altered in MK2(-/-) MEF. Our results further suggest that downregulation of smalpha in MK2(-/-) MEF is not due to lack of activation of serum responsive promoter elements, but probably due to reduced smalpha message stability in these cells. These results indicate that MK2 plays a key role in regulation of smalpha expression, and that targeting MK2 might present a therapeutic approach in managing conditions such as pulmonary fibrosis.

Actins↗

PubMed2006

Characterization of the atypical MAPK ERK4 and its activation of the MAPK-activated protein kinase MK5.

The extracellular-regulated kinase (ERK) 4 (MAPK4) and ERK3 (MAPK6) are structurally related atypical MAPKs displaying major differences only in the C-terminal extension. ERK3 is known as an unstable mostly cytoplasmic protein that binds, translocates, and activates the MAPK-activated protein kinase (MK) 5. Here we have investigated the stability and expression of ERK4 and have analyzed its ability to bind, translocate, and activate MK5. We show that, in contrast to ERK3, ERK4 is a stable protein that binds to endogenous MK5. Interaction of ERK4 with MK5 leads to translocation of MK5 to the cytoplasm and to its activation by phosphorylation. In transfected HEK293 cells, where overexpressed catalytically dead ERK3 is able to activate MK5, catalytic activity of ERK4 is necessary for activation of MK5, indicating that ERK4 directly phosphorylates MK5. Interestingly, ERK4 dimerizes and/or oligomerizes with ERK3, suggesting that overexpressed inactive ERK3 recruits active endogenous ERK4 to MK5 for its activation. Hence, ERK3 and ERK4 cooperate in activation of MK5.

Cell Line↗

PubMed2006

MAPKAP kinase 2-deficient mice are resistant to collagen-induced arthritis.

TNF-alpha is a pleiotropic cytokine considered a primary mediator of immune regulation and inflammatory response and has been shown to play a central role in rheumatoid arthritis (RA). MAPKAP kinase 2 (MK2) is a serine/threonine kinase that is regulated through direct phosphorylation by p38 MAPK, and has been shown to be an essential component in the inflammatory response that regulates the biosynthesis of TNF-alpha at a posttranscriptional level. The murine model of collagen-induced arthritis (CIA) is an established disease model to study pathogenic mechanisms relevant to RA. In this study, we report that deletion of the MK2 gene in DBA/1LacJ mice confers protection against CIA. Interestingly, the MK2 heterozygous mutants display an intermediate level of protection when compared with homozygous mutant and wild-type littermates. We show that MK2(-/-) and MK2(+/-) mice exhibit decreased disease incidence and severity in the CIA disease model and reduced TNF-alpha and IL-6 serum levels following LPS/d-Gal treatment compared with wild-type mice. Additionally, we show that levels of IL-6 mRNA in paws of mice with CIA correlate with the disease status. These findings suggest that an MK2 inhibitor could be of great therapeutic value to treat inflammatory diseases like RA.

Animals↗

PubMed2006

Analysis of properties of small heat shock protein Hsp25 in MAPK-activated protein kinase 2 (MK2)-deficient cells: MK2-dependent insolubilization of Hsp25 oligomers correlates with susceptibility to stress.

Small heat shock proteins (sHsps) exist in dynamic oligomeric complexes and display diverse biological functions ranging from chaperone properties to modulator of apoptosis. So far, the role of stress-dependent phosphorylation of mammalian sHsps for its structure and function has been analyzed by using various phosphorylation site mutants overexpressed in different cell types as well as by non-exclusive inhibitors of the p38 MAPK cascade. Here we investigate the role of phosphorylation of endogenous sHsp in a genetic model lacking the major Hsp25 kinase, the MAP kinase-activated protein kinase MK2. We demonstrate that in MK2-deficient fibroblasts, where no stress-dependent phosphorylation of Hsp25 at Ser86 and no in vitro binding to 14-3-3 was detectable, stress-dependent disaggregation of endogenous Hsp25 complexes is impared and kinetics of arsenite-dependent, H2O2-dependent, and sublethal heat shock-induced insolubilization of Hsp25 is delayed. Similarly, green fluorescent protein-tagged Hsp25 shows retarded subcellular accumulation into stress granules in MK2-deficient cells after arsenite treatment. Decreased insolubilization of Hsp25 in MK2-deficient cells correlates with increased resistance against arsenite, H2O2, and sublethal heat shock treatment and with decreased apoptosis. In contrast, after severe, lethal heat shock MK2-deficient embryonic fibroblasts cells show fast and complete insolubilization of Hsp25 independent of MK2 and no increased stress resistance. Hence, MK2-dependent formation of insoluble stress granules and irreversible cell damage by oxidative stresses and sublethal heat shock correlate and only upon severe, lethal heat shock MK2-independent processes could determine insolubilization of Hsp25 and are more relevant for cellular stress damage.

14-3-3 Proteins↗

PubMed2006

Activation of p38 mitogen-activated protein kinase contributes to the early cardiodepressant action of tumor necrosis factor.

OBJECTIVES: The purpose of this study was to determine whether p38 mitogen-activated protein kinase (p38-MAPK) contributes to tumor necrosis factor-alpha (TNFalpha)-induced contractile depression. BACKGROUND: Tumor necrosis factor has both beneficial and detrimental consequences that may result from the activation of different downstream pathways. Tumor necrosis factor activates p38-MAPK, a stress-responsive kinase implicated in contractile depression and cardiac injury. METHODS: In isolated hearts from mice lacking the p38-MAPK activator, MAPK kinase 3 (MKK3), perfused at constant coronary pressure or flow, we measured the left ventricular developed pressure (LVDP) and the relationship between end-diastolic volume and LVDP in the presence and absence of 10 ng/ml TNFalpha. RESULTS: Within 15 min at constant pressure, TNFalpha significantly reduced LVDP and coronary flow in outbred and mkk3(+/+) mice. This early negative inotropic effect was associated with a marked phosphorylation of both p38-MAPK and its indirect substrate, HSP27. In hearts lacking MKK3, TNFalpha failed to activate p38-MAPK or to cause significant contractile dysfunction. The actions of TNFalpha were similarly attenuated in MAPK-activated protein kinase 2 (MK2)-deficient hearts, which have a marked reduction in myocardial p38-MAPK protein content, and by the p38-MAPK catalytic site inhibitor SB203580 (1 micromol/l). Under conditions of constant coronary flow, the p38-MAPK activation and contractile depression induced by TNFalpha, though attenuated, remained sensitive to the absence of MKK3 or the presence of SB203580. The role of p38-MAPK in TNFalpha-induced contractile depression was confirmed in isolated murine cardiac myocytes exposed to SB203580 or lacking MKK3. CONCLUSIONS: Tumor necrosis factor activates p38-MAPK in the intact heart and in isolated cardiac myocytes through MKK3. This activation likely contributes to the early cardiodepressant action of TNFalpha.

Animals↗

PubMed2006

MAPK-activated protein kinase 2 deficiency in microglia inhibits pro-inflammatory mediator release and resultant neurotoxicity. Relevance to neuroinflammation in a transgenic mouse model of Alzheimer disease.

MAPK-activated protein kinase 2 (MAPKAP K2 or MK2) is one of several kinases directly regulated by p38 MAPK. A role for p38 MAPK in the pathology of Alzheimer disease (AD) has previously been suggested. Here, we provide evidence to suggest that MK2 also plays a role in neuroinflammatory and neurodegenerative pathology of relevance to AD. MK2 activation and expression were increased in lipopolysaccharide (LPS) + interferon gamma-stimulated microglial cells, implicating a role for MK2 in eliciting a pro-inflammatory response. Microglia cultured ex vivo from MK2-deficient (MK2-/-) mice demonstrated significant inhibition in release of tumor necrosis factor alpha, KC (mouse chemokine with highest sequence identity to human GROs and interleukin-8), and macrophage inflammatory protein 1alpha on stimulation with LPS + interferon gamma or amyloid-beta peptide (1-42) compared with MK2+/+ wild-type microglia. Consistent with an inhibition in pro-inflammatory mediator release, cortical neurons co-cultured with LPS + interferon gamma-stimulated or amyloid-beta peptide (1-42)-stimulated MK2-/- microglia were protected from microglial-mediated neuronal cell toxicity. In a transgenic mouse model of AD in which amyloid precursor protein and presenilin-1 harboring familial AD mutations are overexpressed in specific regions of the brain, elevated activation and expression of MK2 correlated with beta-amyloid deposition, microglial activation, and up-regulation of tumor necrosis factor alpha, macrophage inflammatory protein 1alpha, and KC gene expression in the same brain regions. Our data propose a role for MK2 in AD brain pathology, for which neuroinflammation involving cytokines and chemokines and overt neuronal loss have been documented.

Alzheimer Disease↗

PubMed2006

CXCL12 and C5a trigger cell migration via a PAK1/2-p38alpha MAPK-MAPKAP-K2-HSP27 pathway.

Cell migration is critical for many processes, such as angiogenesis, inflammation, development and wound healing, and is also involved in tumour progression and metastasis. Here we show that CXCL12, complement factor 5a (C5a), hepatocyte growth factor (HGF) and platelet-derived growth factor (PDGF)-BB, which stimulate cell migration, also activate p38alpha MAPK. Pharmacological inhibition of this protein kinase with SB 203580 or BIRB 0796, or the genetic ablation of p38alpha MAPK, blocked cell migration induced by the aforementioned chemo-attractants. Macrophages from mice lacking one or more of the other p38 MAPK isoforms showed normal cell migration in response to C5a. We also show that the activation of p38alpha MAPK in response to CXCL12 requires the p21-activated protein kinases (PAK)-1 and PAK-2. MAPKAP-K2 is a protein kinase that is activated by p38alpha MAPK. Reducing its expression using RNA interference blocked CXCL12-induced HeLa cell migration, while macrophages from mice that do not express MAPKAP-K2 failed to migrate in response to C5a. Moreover, RNA interference against the small heat shock protein 27 (HSP27), a physiological substrate of MAPKAP-K2, blocked the CXCL12-induced cell migration. These results demonstrate a general and essential role of the PAK-p38alpha MAPK-MAPKAP-K2-HSP27 signalling pathway in mediating the effects of chemotactic stimuli on cell migration.

Animals↗

PubMed2006

Gene deletion of MK2 inhibits TNF-alpha and IL-6 and protects against cerulein-induced pancreatitis.

Inflammatory effects contribute to the pathogenesis of pancreatitis. Clearly, proinflammatory cytokines like TNF-alpha and IL-6 are involved in this process and the associated systemic complications. The MAPKAPK-2 (MK2) signaling pathway is involved in cytokine gene expression. Therefore, we hypothesized that blockade of this pathway inhibits the expression of proinflammatory cytokines and thereby protects against pancreatitis. To investigate this, we used an in vivo mouse model with a homozygous deletion of the MK2 gene. Pancreatitis was induced by injection of cerulein. The severity was determined by measuring serum lipase, pancreatic trypsin activation, pancreatic edema, and morphological changes by quantitative scoring of histological sections. Systemic inflammation was evaluated by measuring myeloperoxidase activity in lung tissue. Serum levels of TNF-alpha and IL-6 were measured using an ELISA, and mRNA levels were identified using RT-PCR and subsequent quantitative PCR analysis. Pancreatitis in animals with deletion of the MK2 gene is less severe and accompanied with reduced serum levels of TNF-alpha and IL-6. Pancreatic mRNA levels revealed a fourfold reduction of IL-6 mRNA expression in MK2 -/- mice. Effects were associated with suppression of pancreatic trypsin activity and reduced acinar cell injury. In summary, these data show that gene deletion of MK2 ameliorates cerulein-induced pancreatitis. TNF-alpha and IL-6 signaling is mediated by the MK2 pathway and therefore crucial for the regulatory inflammatory processes. TNF-alpha expression is supposably regulated by a posttranscriptional mechanism, whereas IL-6 expression is most likely regulated by transcriptional effects.

Animals↗

PubMed2006

MAPKAP kinases - MKs - two's company, three's a crowd.

Downstream of mitogen-activated protein kinases (MAPKs), three structurally related MAPK-activated protein kinases (MAPKAPKs or MKs) - MK2, MK3 and MK5 - signal to diverse cellular targets. Although there is no known common function for all three MKs, these kinases are involved in important processes: MKs regulate gene expression at the transcriptional and post-transcriptional level, control cytoskeletal architecture and cell-cycle progression, and are implicated in inflammation and cancer.

14-3-3 Proteins↗

PubMed2006

Mitogen-activated protein kinase-activated protein kinase 2 regulates tumor necrosis factor mRNA stability and translation mainly by altering tristetraprolin expression, stability, and binding to adenine/uridine-rich element.

The mitogen-activated protein kinase (MAPK) p38/MAPK-activated protein kinase 2 (MK2) signaling pathway plays an important role in the posttranscriptional regulation of tumor necrosis factor (TNF), which is dependent on the adenine/uridine-rich element (ARE) in the 3' untranslated region of TNF mRNA. After lipopolysaccharide (LPS) stimulation, MK2-deficient macrophages show a 90% reduction in TNF production compared to the wild type. Tristetraprolin (TTP), a protein induced by LPS, binds ARE and destabilizes TNF mRNA. Accordingly, macrophages lacking TTP produce large amounts of TNF. Here, we generated MK2/TTP double knockout mice and show that, after LPS stimulation, bone marrow-derived macrophages produce TNF mRNA and protein levels comparable to those of TTP knockout cells, indicating that in the regulation of TNF biosynthesis TTP is genetically downstream of MK2. In addition, we show that MK2 is essential for the stabilization of TTP mRNA, and phosphorylation by MK2 leads to increased TTP protein stability but reduced ARE affinity. These data suggest that MK2 inhibits the mRNA destabilizing activity of TTP and, in parallel, codegradation of TTP together, with the target mRNA resulting in increased cellular levels of TTP.

3' Untranslated Regions↗

PubMed2005

Phosphorylation of HSF1 by MAPK-activated protein kinase 2 on serine 121, inhibits transcriptional activity and promotes HSP90 binding.

Heat shock transcription factor 1 (HSF1) monitors the structural integrity of intracellular proteins and its regulation is essential for the health and longevity of eukaryotic organisms. HSF1 also plays a role in the acute inflammatory response in the negative regulation of cytokine gene transcription. Here we show, for the first time, that HSF1 is regulated by the proinflammatory protein kinase MAPKAP kinase 2 (MK2). We have shown that MK2 directly phosphorylates HSF1 and inhibits activity by decreasing its ability to bind the heat shock elements (HSE) found in the promoters of target genes encoding the HSP molecular chaperones and cytokine genes. We show that activation of HSF1 to bind HSE in hsp promoters is inhibited through the phosphorylation of a specific residue, serine 121 by MK2. A potential mechanism for MK2-induced HSF1 inactivation is suggested by the findings that phosphorylation of serine 121 enhances HSF1 binding to HSP90, a major repressor of HSF1. Dephosphorylation of serine 121 in cells exposed to non-steroidal anti-inflammatory drugs leads to HSP90 dissociation from HSF1, which then forms active DNA binding trimers. These experiments indicate a novel mechanism for the regulation of HSF1 by proinflammatory signaling and may permit HSF1 to respond rapidly to extracellular events, permitting optimal physiological regulation.

Amino Acid Sequence↗

PubMed2005

Hypoxia alters biophysical properties of endothelial cells via p38 MAPK- and Rho kinase-dependent pathways.

Hypoxia alters the barrier function of the endothelial cells that line the pulmonary vasculature, but underlying biophysical mechanisms remain unclear. Using rat pulmonary microvascular endothelial cells (RPMEC) in culture, we report herein changes in biophysical properties, both in space and in time, that occur in response to hypoxia. We address also the molecular basis of these changes. At the level of the single cell, we measured cell stiffness, the distribution of traction forces exerted by the cell on its substrate, and spontaneous nanoscale motions of microbeads tightly bound to the cytoskeleton (CSK). Hypoxia increased cell stiffness and traction forces by a mechanism that was dependent on the activation of Rho kinase. These changes were followed by p38-mediated decreases in spontaneous bead motions, indicating stabilization of local cellular-extracellular matrix (ECM) tethering interactions. Cells overexpressing phospho-mimicking small heat shock protein (HSP27-PM), a downstream effector of p38, exhibited decreases in spontaneous bead motions that correlated with increases in actin polymerization in these cells. Together, these findings suggest that hypoxia differentially regulates endothelial cell contraction and cellular-ECM adhesion.

Animals↗

PubMed2005

HDM2 phosphorylation by MAPKAP kinase 2.

p53 stability is regulated by HDM2, a RING domain protein that acts as an E3 ligase to ubiquitinate p53 and target its degradation. Phosphorylation of HDM2 on serine 166 by AKT has been shown to enhance HDM2 activity and promote the degradation of p53. Here, we show that MAPKAP kinase 2 (MK2) can phosphorylate HDM2 on serine 157 and 166 in vitro. Treatment of cells with anisomycin, which activates MK2, also results in phosphorylation of HDM2 on serine 157 and 166 in vivo. Mutation of the MK2 phosphorylation sites in HDM2 to aspartic acid renders HDM2 slightly more active in the degradation of p53, and mouse cells deficient for MK2 show reduced Mdm2 phosphorylation and elevated levels of p53 protein. Together, our results suggest that MK2 may act to dampen the extent and duration of the p53 response.

Animals↗

PubMed2005

Activation of mitogen-activated protein kinase kinase (MKK) 3 and MKK6 by type I interferons.

There is accumulating evidence that the p38 MAP kinase pathway plays important roles in Type I interferon (IFN) signaling, but the mechanisms regulating p38 activation during engagement of the Type I IFN receptor remain to be defined. We sought to identify the events that lead to activation of the p38 MAP kinase in response to Type I IFNs. Our data demonstrate that treatment of sensitive cell lines with IFNalpha results in activation of both MAP kinase kinase 3 (MKK3) and MAP kinase kinase 6 (MKK6). Such IFN-inducible activation of MKK3 and MKK6 is essential for downstream phosphorylation and activation of the p38 MAP kinase, as shown by studies using mouse embryonic fibroblasts (MEFs) with targeted disruption of the Mkk3 and Mkk6 genes (MKK3-/- MKK6-/-). Similarly, IFN-dependent activation of the downstream effectors of p38, MAPKAPK-2 and MAPKAPK-3, is not detectable in cells lacking Mkk3 and Mkk6, demonstrating that the function of these MAP kinase kinases is required for full activation of the p38 pathway. To define the functional relevance of MKK3/6 engagement in Type I IFN signaling, IFN-inducible gene transcription was evaluated in the MKK3/MKK6 double knock-out cells. IFNalpha- and IFNbeta-dependent transcription via either interferon-stimulated response element or IFNgamma activated site elements was defective in MKK3 -/-/MKK6 -/- MEFs in luciferase reporter assays. In addition, IFN-dependent induction of two genes known to be of importance in the generation of IFN responses, Isg15 and Irf-9, was diminished in the absence of Mkk3 and Mkk6. The effects of Mkk3 and Mkk6 on IFN-dependent transcription were unrelated to any effects on the phosphorylation and activation of STAT proteins, indicating the presence of a STAT-independent mechanism. Altogether, our findings demonstrate that MKK3 and MKK6 are rapidly activated during engagement of the Type I IFN receptor and play important roles in Type I IFN signaling and the generation of IFN responses.

Animals↗

PubMed2004

Scaffolding by ERK3 regulates MK5 in development.

Extracellular-regulated kinase 3 (ERK3, MAPK6) is an atypical member of the ERKs, lacking the threonine and tyrosine residues in the activation loop, carrying a unique C-terminal extension and being mainly regulated by its own protein stability and/or by autophosphorylation. Here we show that ERK3 specifically interacts with the MAPK-activated protein kinase 5 (MK5 or PRAK) in vitro and in vivo. Expression of ERK3 in mammalian cells leads to nuclear-cytoplasmic translocation and activation of MK5 and to phosphorylation of both ERK3 and MK5. Remarkably, activation of MK5 is independent of ERK3 enzymatic activity, but depends on its own catalytic activity as well as on a region in the C-terminal extension of ERK3. In mouse embryonic development, mRNA expression patterns of ERK3 and MK5 suggest spatiotemporal coexpression of both kinases. Deletion of MK5 leads to strong reduction of ERK3 protein levels and embryonic lethality at about stage E11, where ERK3 expression in wild-type mice is maximum, indicating a role of this signalling module in development.

Animals↗

PubMed2004

P66(ShcA) interacts with MAPKAP kinase 2 and regulates its activity.

Three mitogen activated protein kinase-activated protein kinase 2 (MAPKAP kinase 2, MK2) interacting proteins were identified using a yeast two-hybrid approach. ShcA, a signaling phospho-protein, human polyhomeotic 2 (HPH2), a transcriptional regulator, and highly similar to smoothelin (HSTS), which is related to the cytoskeletal associated protein smoothelin, interact specifically with MK2. The interaction of MK2 with the 66 kDa isoform of ShcA, p66(ShcA), and HPH2 was confirmed using co-immunoprecipitation. MK2 is activated with p66(ShcA) co-expression and p66(ShcA) is an in vitro substrate for MK2, further demonstrating their association and suggesting a biological role for p66(Shc) in MK2 activation.

Adaptor Proteins, Signal Transducing↗

PubMed2004

A requirement of MAPKAPK2 in the uropod localization of PTEN during FMLP-induced neutrophil chemotaxis.

The directionality control in chemotaxis is the result of a reciprocal regulation of PI3-kinase and PTEN subcellular localization. MK2(-/-) neutrophils have a directionality loss in fMLP-induced chemotaxis. We found that in polarized WT neutrophils PTEN was localized in the uropod region. However, MK2(-/-) neutrophils or p38 MAPK inhibitor-SB203580-pretreated WT neutrophils showed a disrupted PTEN subcellular localization. Some PTEN was localized at the leading edge of the polarized neutrophils, which may lower the concentration of PI3-kinase lipid product PtdIns(3,4,5)P3 required for directionality sensing. FMLP-stimulated MK2(-/-) neutrophils or SB203580-pretreated WT neutrophils also had disrupted F-actin polarization. F-actin polymerization inhibitor lantrunculin-B disrupted the polarization of PTEN, but not PtdIns(3,4,5)P3. The results suggest that PTEN uropod polarization is F-actin polymerization-dependent and may be through the effect of MK2 on F-actin polarization.

Actins↗

PubMed2004

Role of heat shock protein 27 in cytoskeletal remodeling of the airway smooth muscle cell.

Remodeling of the airway smooth muscle (ASM) cell has been proposed to play an important role in airway hyperresponsiveness. Using a functional assay, we have assessed remodeling of the cultured rat ASM cell and the role of heat shock protein (HSP) 27 in that process. To probe remodeling dynamics, we measured spontaneous motions of an individual Arg-Gly-Asp-coated microbead that was anchored to the cytoskeleton. We reasoned that the bead could not move unless the microstructure to which it is attached rearranged; if so, then its mean square displacement (MSD) would report ongoing internal reorganizations over time. Each bead displayed a random, superdiffusive motion; MSD increased with time as approximately t(1.7), whereas an exponent of unity would be expected for a simple passive diffusion. Increasing concentrations of cytochalasin-D or latrunculin-A caused marked increases in the MSD, whereas colchicine did not. Treatments with PDGF or IL-1beta, but not transforming growth factor-beta, caused decreases in the MSD, the extent of which rank-ordered with the relative potency of these agents in eliciting the phosphorylation of HSP27. The chemical stressors anisomycin and arsenite each increased the levels of HSP27 phosphorylation and, at the same time, decreased bead motions. In particular, arsenite prevented and even reversed the effects of cytochalasin-D on bead motions. Finally, ASM cells overexpressing phospho-mimicking human HSP27, but not wild-type or phosphorylation-deficient HSP27, exhibited decreases in bead motions that were comparable to the arsenite response. Taken together, these results show that phosphorylated HSP27 favors reduced bead motions that are probably due to stabilization of the actin cytoskeleton.

Animals↗