Jason E Gestwicki

Publications (74)420.46 Total impact

• Article: Allosteric Heat Shock Protein 70 Inhibitors Rapidly Rescue Synaptic Plasticity Deficits by Reducing Aberrant Tau.

  Jose Abisambra, Umesh K Jinwal, Yoshinari Miyata, Justin Rogers, Laura Blair, Xiaokai Li, Sandlin P Seguin, Li Wang, Ying Jin, Justin Bacon, [......], Juan Zhang, John Koren, Zapporah T Young, Christopher A Atkins, Bo Zhang, Lisa Y Lawson, Edwin J Weeber, Jeffrey L Brodsky, Jason E Gestwicki, Chad A Dickey
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  ABSTRACT: BACKGROUND: The microtubule-associated protein tau accumulates in neurodegenerative diseases known as tauopathies, the most common being Alzheimer's disease. One way to treat these disorders may be to reduce abnormal tau levels through chaperone manipulation, thus subverting synaptic plasticity defects caused by tau's toxic accretion. METHODS: Tauopathy models were used to study the impact of YM-01 on tau. YM-01 is an allosteric promoter of triage functions of the most abundant variant of the heat shock protein 70 (Hsp70) family in the brain, heat shock cognate 70 protein (Hsc70). The mechanisms by which YM-01 modified Hsc70 activity and tau stability were evaluated with biochemical methods, cell cultures, and primary neuronal cultures from tau transgenic mice. YM-01 was also administered to acute brain slices of tau mice; changes in tau stability and electrophysiological correlates of learning and memory were measured. RESULTS: Tau levels were rapidly and potently reduced in vitro and ex vivo upon treatment with nanomolar concentrations of YM-01. Consistent with Hsc70 having a key role in this process, overexpression of heat shock protein 40 (DNAJB2), an Hsp70 co-chaperone, suppressed YM-01 activity. In contrast to its effects in pathogenic tauopathy models, YM-01 had little activity in ex vivo brain slices from normal, wild-type mice unless microtubules were disrupted, suggesting that Hsc70 acts preferentially on abnormal pools of free tau. Finally, treatment with YM-01 increased long-term potentiation in tau transgenic brain slices. CONCLUSIONS: Therapeutics that exploit the ability of chaperones to selectively target abnormal tau can rapidly and potently rescue the synaptic dysfunction that occurs in Alzheimer's disease and other tauopathies.
  Biological psychiatry 04/2013; · 8.93 Impact Factor
• Article: Synthesis and Initial Evaluation of YM-08, a Blood-Brain Barrier Permeable Derivative of the Heat Shock Protein 70 (Hsp70) Inhibitor MKT-077, Which Reduces Tau Levels.

  Yoshinari Miyata, Xiaokai Li, Hsiu-Fang Lee, Umesh Jinwal, Sharan R Srinivasan, Sandlin P Seguin, Zapporah T Young, Jeffrey L Brodsky, Chad A Dickey, Duxin Sun, Jason E Gestwicki
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  ABSTRACT: The molecular chaperone, heat shock protein 70 (Hsp70), is an emerging drug target for treating multiple diseases, including cancer and neurodegenerative disorders. We recently found that one promising Hsp70 inhibitor, MKT-077, reduces tau levels in cellular models, suggesting its potential for use in treating neurodegenerative diseases that involve aberrant tau accumulation. However, MKT-077 does not penetrate the blood-brain barrier (BBB), limiting its use as either a clinical candidate or probe for exploring Hsp70 as a drug target in the central nervous system (CNS). We hypothesized that replacing the cationic pyridinium moiety in MKT-077 with a neutral pyridine might improve its clogP and enhance its BBB penetrance. To test this idea, we designed and synthesized YM-08, a neutral analog of MKT-077. Like the parent compound, YM-08 bound to Hsp70 in vitro and reduced phosphorylated tau levels in cultured brain slices. Pharmacokinetic evaluation in CD1 mice showed that YM-08 crossed the BBB and maintained a B/P value of ~0.25 for at least 18 hours. Together, these studies suggest that YM-08 is a promising scaffold for the development of Hsp70 inhibitors suitable for use in the CNS.
  ACS Chemical Neuroscience 03/2013; · 3.68 Impact Factor
• Article: Expanding the number of 'druggable' targets: non-enzymes and protein-protein interactions.

  Leah N Makley, Jason E Gestwicki
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  ABSTRACT: Following sequencing and assembly of the human genome, the preferred methods for identification of new drug targets have changed dramatically. Modern tactics such as genome-wide association studies (GWAS) and deep sequencing are fundamentally different from the pharmacology-guided approaches used previously, in which knowledge of small molecule ligands acting at their cellular targets was the primary discovery engine. A consequence of the 'target-first, pharmacology-second' strategy is that many predicted drug targets are non-enzymes, such as scaffolding, regulatory or structural proteins, and their activities are often dependent on protein-protein interactions (PPIs). These types of targets create unique challenges to drug discovery efforts because enzymatic turnover cannot be used as a convenient surrogate for compound potency. Moreover, it is often challenging to predict how ligand binding to non-enzymes might affect changes in protein function and/or pathobiology. Thus, in the postgenomic era, targets might be strongly implicated by molecular biology-based methods, yet they often later earn the designation of 'undruggable'. Can the scope of available targets be widened to include these promising, but challenging, non-enzymes? In this review, we discuss advances in high-throughput screening (HTS) technology and chemical library design that are emerging to deal with these challenges.
  Chemical Biology &amp Drug Design 01/2013; 81(1):22-32. · 2.28 Impact Factor
• Article: Imbalance of Hsp70 family variants fosters tau accumulation.

  Umesh K Jinwal, Elias Akoury, Jose F Abisambra, John C O'Leary, Andrea D Thompson, Laura J Blair, Ying Jin, Justin Bacon, Bryce A Nordhues, Matthew Cockman, Juan Zhang, Pengfei Li, Bo Zhang, Sergiy Borysov, Vladimir N Uversky, Jacek Biernat, Eckhard Mandelkow, Jason E Gestwicki, Markus Zweckstetter, Chad A Dickey
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  ABSTRACT: Dysfunctional tau accumulation is a major contributing factor in tauopathies, and the heat-shock protein 70 (Hsp70) seems to play an important role in this accumulation. Several reports suggest that Hsp70 proteins can cause tau degradation to be accelerated or slowed, but how these opposing activities are controlled is unclear. Here we demonstrate that highly homologous variants in the Hsp70 family can have opposing effects on tau clearance kinetics. When overexpressed in a tetracycline (Tet)-based protein chase model, constitutive heat shock cognate 70 (Hsc70) and inducible Hsp72 slowed or accelerated tau clearance, respectively. Tau synergized with Hsc70, but not Hsp72, to promote microtubule assembly at nearly twice the rate of either Hsp70 homologue in reconstituted, ATP-regenerating Xenopus extracts supplemented with rhodamine-labeled tubulin and human recombinant Hsp72 and Hsc70. Nuclear magnetic resonance spectroscopy with human recombinant protein revealed that Hsp72 had greater affinity for tau than Hsc70 (I/I(0) ratio difference of 0.3), but Hsc70 was 30 times more abundant than Hsp72 in human and mouse brain tissue. This indicates that the predominant Hsp70 variant in the brain is Hsc70, suggesting that the brain environment primarily supports slower tau clearance. Despite its capacity to clear tau, Hsp72 was not induced in the Alzheimer's disease brain, suggesting a mechanism for age-associated onset of the disease. Through the use of chimeras that blended the domains of Hsp72 and Hsc70, we determined that the reason for these differences between Hsc70 and Hsp72 with regard to tau clearance kinetics lies within their C-terminal domains, which are essential for their interactions with substrates and cochaperones. Hsp72 but not Hsc70 in the presence of tau was able to recruit the cochaperone ubiquitin ligase CHIP, which is known to facilitate the ubiquitination of tau, describing a possible mechanism of how the C-termini of these homologous Hsp70 variants can differentially regulate tau triage. Thus, efforts to promote Hsp72 expression and inhibit Hsc70 could be therapeutically relevant for tauopathies.-Jinwal, U. K., Akoury, E., Abisambra, J. F., O'Leary, J. C., III, Thompson, A. D., Blair, L. J., Jin, Y., Bacon, J., Nordhues, B. A., Cockman, M., Zhang, J., Li, P., Zhang, B., Borysov, S., Uversky, V. N., Biernat, J., Mandelkow, E., Gestwicki, J. E., Zweckstetter, M., Dickey, C. A. Imbalance of Hsp70 family variants fosters tau accumulation.
  The FASEB Journal 12/2012; · 5.71 Impact Factor
• Article: Activation of Hsp70 reduces neurotoxicity by promoting polyglutamine protein degradation.

  Adrienne M Wang, Yoshinari Miyata, Susan Klinedinst, Hwei-Ming Peng, Jason P Chua, Tomoko Komiyama, Xiaokai Li, Yoshihiro Morishima, Diane E Merry, William B Pratt, Yoichi Osawa, Catherine A Collins, Jason E Gestwicki, Andrew P Lieberman
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  ABSTRACT: We sought new strategies to reduce amounts of the polyglutamine androgen receptor (polyQ AR) and achieve benefits in models of spinobulbar muscular atrophy, a protein aggregation neurodegenerative disorder. Proteostasis of the polyQ AR is controlled by the heat shock protein 90 (Hsp90)- and Hsp70-based chaperone machinery, but mechanisms regulating the protein's turnover are incompletely understood. We demonstrate that overexpression of Hsp70 interacting protein (Hip), a co-chaperone that enhances binding of Hsp70 to its substrates, promotes client protein ubiquitination and polyQ AR clearance. Furthermore, we identify a small molecule that acts similarly to Hip by allosterically promoting Hsp70 binding to unfolded substrates. Like Hip, this synthetic co-chaperone enhances client protein ubiquitination and polyQ AR degradation. Both genetic and pharmacologic approaches targeting Hsp70 alleviate toxicity in a Drosophila model of spinobulbar muscular atrophy. These findings highlight the therapeutic potential of allosteric regulators of Hsp70 and provide new insights into the role of the chaperone machinery in protein quality control.
  Nature Chemical Biology 12/2012; · 14.69 Impact Factor
• Article: Cysteine reactivity distinguishes redox sensing by the heat-inducible and constitutive forms of heat shock protein 70.

  Yoshinari Miyata, Jennifer N Rauch, Umesh K Jinwal, Andrea D Thompson, Sharan Srinivasan, Chad A Dickey, Jason E Gestwicki
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  ABSTRACT: The heat shock protein 70 (Hsp70) family of molecular chaperones has important functions in maintaining proteostasis under stress conditions. Several Hsp70 isoforms, especially Hsp72 (HSPA1A), are dramatically upregulated in response to stress; however, it is unclear whether these family members have biochemical properties that are specifically adapted to these scenarios. The redox-active compound, methylene blue (MB), has been shown to inhibit the ATPase activity of Hsp72 in vitro, and it promotes degradation of the Hsp72 substrate, tau, in cellular and animal models. Here, we report that MB irreversibly inactivates Hsp72 but not the nearly identical, constitutively expressed isoform, heat shock cognate 70 (Hsc70; HSPA8). Mass spectrometry results show that MB oxidizes Cys306, which is not conserved in Hsc70. Molecular models suggested that oxidation of Cys306 exposes Cys267 to modification and that both events contribute to loss of ATP binding in response to MB. Consistent with this model, mutating Cys267 and Cys306 to serine made Hsp72 largely resistant to MB in vitro, and overexpression of the C306S mutant blocked MB-mediated loss of tau in a cellular model. Furthermore, mutating Cys267 and Cys306 to the pseudo-oxidation mimic, aspartic acid, mirrored MB treatment: the C267D and C306D mutants had reduced ATPase activity in vitro, and overexpression of the C267/306D double mutant significantly reduced tau levels in cells. Together, these results suggest that redox sensing by specific cysteine residues in Hsp72, but not Hsc70, may be an important component of the chaperone response to oxidative stress.
  Chemistry & biology 11/2012; 19(11):1391-9. · 6.52 Impact Factor
• Article: Hsp70 Protein Complexes as Drug Targets.

  Victoria A Assimon, Anne T Gillies, Jennifer N Rauch, Jason E Gestwicki
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  ABSTRACT: Heat shock protein 70 (Hsp70) plays critical roles in proteostasis and is an emerging target for multiple diseases. However, competitive inhibition of the enzymatic activity of Hsp70 has proven challenging and, in some cases, may not be the most productive way to redirect Hsp70 function. Another approach is to inhibit Hsp70's interactions with important co-chaperones, such as J proteins, nucleotide exchange factors (NEFs) and tetratricopeptide repeat (TPR) domain-containing proteins. These co-chaperones normally bind Hsp70 and guide its many diverse cellular activities. Complexes between Hsp70 and co-chaperones have been shown to have specific functions, such as pro-folding, pro-degradation and pro-trafficking. Thus, a promising strategy may be to block protein-protein interactions between Hsp70 and its co-chaperones or to target allosteric sites that disrupt these contacts. Such an approach might shift the balance of Hsp70 complexes and re-shape the proteome and it has the potential to restore healthy proteostasis. In this review, we discuss specific challenges and opportunities related to those goals. By pursuing Hsp70 complexes as drug targets, we might not only develop new leads for therapeutic development, but also discover new chemical probes for use in understanding Hsp70 biology.
  Current pharmaceutical design 08/2012; · 4.41 Impact Factor
• Article: A screen for modulators of large T antigen's ATPase activity uncovers novel inhibitors of Simian Virus 40 and BK virus replication.

  Sandlin P Seguin, Alex W Ireland, Tushar Gupta, Christine M Wright, Yoshinari Miyata, Peter Wipf, James M Pipas, Jason E Gestwicki, Jeffrey L Brodsky
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  ABSTRACT: New polyomaviruses are continually being identified, and it is likely that links between this virus family and disease will continue to emerge. Unfortunately, a specific treatment for polyomavirus-associated disease is lacking. Because polyomaviruses express large Tumor Antigen, TAg, we hypothesized that small molecule inhibitors of the essential ATPase activity of TAg would inhibit viral replication. Using a new screening platform, we identified inhibitors of TAg's ATPase activity. Lead compounds were moved into a secondary assay, and ultimately two FDA approved compounds, bithionol and hexachlorophene, were identified as the most potent TAg inhibitors known to date. Both compounds inhibited Simian Virus 40 replication as assessed by plaque assay and quantitative PCR. Moreover, these compounds inhibited BK virus, which causes BKV Associated Nephropathy. In neither case was host cell viability compromised at these concentrations. Our data indicate that directed screening for TAg inhibitors is a viable method to identify polyomavirus inhibitors, and that bithionol and hexachlorophene represent lead compounds that may be further modified and/or ultimately used to combat diseases associated with polyomavirus infection.
  Antiviral research 08/2012; 96(1):70-81. · 3.61 Impact Factor
• Article: Synthetic lethal interactions in yeast reveal functional roles of J protein co-chaperones.

  Anne T Gillies, Rebecca Taylor, Jason E Gestwicki
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  ABSTRACT: J proteins are a diverse family of co-chaperones that cooperate with heat shock protein 70 (Hsp70) to coordinate protein quality control, especially in response to cellular stress. Current models suggest that individual J proteins might play roles in recruiting Hsp70s to specific functions, such as maintaining cell wall integrity or promoting ribosome biogenesis. However, relatively few stresses have been used to test this model and, as a result, only a few specific activities have been identified. To expand our understanding of the J protein network, we used a synthetic lethal approach in which 11 Saccharomyces cerevisiae deletion strains were treated with 12 well-characterized chemical inhibitors. The results defined new roles for specific J proteins in major signaling pathways. For example, an important role for Swa2 in cell wall integrity was identified and activities of the under-explored Jjj1, Apj1, Jjj3 and Caj1 proteins were suggested. More generally, these findings support a model in which some J proteins, such as Ydj1 and Zuo1, play "generalist" roles, while others, such as Apj1 and Jjj2, are "specialists", having roles in relatively few pathways. Together, these results provide new insight into the network of J proteins.
  Molecular BioSystems 08/2012; 8(11):2901-8. · 3.53 Impact Factor
• Article: Analysis of the tau-associated proteome reveals that exchange of hsp70 for hsp90 is involved in tau degradation.

  Andrea D Thompson, K Matthew Scaglione, John Prensner, Anne T Gillies, Arul Chinnaiyan, Henry L Paulson, Umesh K Jinwal, Chad A Dickey, Jason E Gestwicki
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  ABSTRACT: The microtubule associated protein tau (MAPT/tau) aberrantly accumulates in 15 neurodegenerative diseases, termed tauopathies. One way to treat tauopathies may be to accelerate tau clearance, but the molecular mechanisms governing tau stability are not yet clear. We recently identified chemical probes that markedly accelerate the clearance of tau in cellular and animal models. In the current study, we used one of these probes in combination with immunoprecipitation and mass spectrometry to identify 48 proteins whose association with tau changes during the first 10 min after treatment. These proteins included known modifiers of tau proteotoxicity, such as ILF-2 (NFAT), ILF-3, and ataxin-2. A striking observation from the data set was that tau binding to heat shock protein 70 (Hsp70) decreased, whereas binding to Hsp90 significantly increased. Both chaperones have been linked to tau homeostasis, but their mechanisms have not been established. Using peptide arrays and binding assays, we found that Hsp70 and Hsp90 appeared to compete for binding to shared sites on tau. Further, the Hsp90-bound complex proved to be important in initiating tau clearance in cells. These results suggest that the relative levels of Hsp70 and Hsp90 may help determine whether tau is retained or degraded. Consistent with this model, analysis of reported microarray expression data from Alzheimer's disease patients and age-matched controls showed that the levels of Hsp90 are reduced in the diseased hippocampus. These studies suggest that Hsp70 and Hsp90 work together to coordinate tau homeostasis.
  ACS Chemical Biology 07/2012; 7(10):1677-86. · 6.45 Impact Factor
• Article: Molecular chaperones DnaK and DnaJ share predicted binding sites on most proteins in the E. coli proteome.

  Sharan R Srinivasan, Anne T Gillies, Lyra Chang, Andrea D Thompson, Jason E Gestwicki
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  ABSTRACT: In Escherichia coli, the molecular chaperones DnaK and DnaJ cooperate to assist the folding of newly synthesized or unfolded polypeptides. DnaK and DnaJ bind to hydrophobic motifs in these proteins and they also bind to each other. Together, this system is thought to be sufficiently versatile to act on the entire proteome, which creates interesting challenges in understanding the interactions between DnaK, DnaJ and their thousands of potential substrates. To address this question, we computationally predicted the number and frequency of DnaK- and DnaJ-binding motifs in the E. coli proteome, guided by free energy-based binding consensus motifs. This analysis revealed that nearly every protein is predicted to contain multiple DnaK- and DnaJ-binding sites, with the DnaJ sites occurring approximately twice as often. Further, we found that an overwhelming majority of the DnaK sites partially or completely overlapped with the DnaJ-binding motifs. It is well known that high concentrations of DnaJ inhibit DnaK-DnaJ-mediated refolding. The observed overlapping binding sites suggest that this phenomenon may be explained by an important balance in the relative stoichiometry of DnaK and DnaJ. To test this idea, we measured the chaperone-assisted folding of two denatured substrates and found that the distribution of predicted DnaK- and DnaJ-binding sites was indeed a good predictor of the optimal stoichiometry required for folding. These studies provide insight into how DnaK and DnaJ might cooperate to maintain global protein homeostasis.
  Molecular BioSystems 06/2012; 8(9):2323-33. · 3.53 Impact Factor
• Article: Fine-tuning multiprotein complexes using small molecules.

  Andrea D Thompson, Amanda Dugan, Jason E Gestwicki, Anna K Mapp
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  ABSTRACT: Multiprotein complexes such as the transcriptional machinery, signaling hubs, and protein folding machines are typically composed of at least one enzyme combined with multiple non-enzymes. Often the components of these complexes are incorporated in a combinatorial manner, in which the ultimate composition of the system helps dictate the type, location, or duration of cellular activities. Although drugs and chemical probes have traditionally targeted the enzyme components, emerging strategies call for controlling the function of protein complexes by modulation of protein-protein interactions (PPIs). However, the challenges of targeting PPIs have been well documented, and the diversity of PPIs makes a "one-size-fits-all" solution highly unlikely. These hurdles are particularly daunting for PPIs that encompass large buried surface areas and those with weak affinities. In this Review, we discuss lessons from natural systems, in which allostery and other mechanisms are used to overcome the challenge of regulating the most difficult PPIs. These systems may provide a blueprint for identifying small molecules that target challenging PPIs and affecting molecular decision-making within multiprotein systems.
  ACS Chemical Biology 06/2012; 7(8):1311-20. · 6.45 Impact Factor
• Article: Pharmacological tuning of heat shock protein 70 modulates polyglutamine toxicity and aggregation.

  Sidhartha M Chafekar, Susanne Wisén, Andrea D Thompson, Analisa Echeverria, Gladis M Walter, Christopher G Evans, Leah N Makley, Jason E Gestwicki, Martin L Duennwald
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  ABSTRACT: Nine neurodegenerative disorders are caused by the abnormal expansion of polyglutamine (polyQ) regions within distinct proteins. Genetic and biochemical evidence has documented that the molecular chaperone, heat shock protein 70 (Hsp70), modulates polyQ toxicity and aggregation, yet it remains unclear how Hsp70 might be used as a potential therapeutic target in polyQ-related diseases. We have utilized a pair of membrane-permeable compounds that tune the activity of Hsp70 by either stimulating or by inhibiting its ATPase functions. Using these two pharmacological agents in both yeast and PC12 cell models of polyQ aggregation and toxicity, we were surprised to find that stimulating Hsp70 solubilized polyQ conformers and simultaneously exacerbated polyQ-mediated toxicity. By contrast, inhibiting Hsp70 ATPase activity protected against polyQ toxicity and promoted aggregation. These findings clarify the role of Hsp70 as a possible drug target in polyQ disorders and suggest that Hsp70 uses ATP hydrolysis to help partition polyQ proteins into structures with varying levels of proteotoxicity. Our results thus support an emerging concept in which certain kinds of polyQ aggregates may be protective, while more soluble polyQ species are toxic.
  ACS Chemical Biology 06/2012; 7(9):1556-64. · 6.45 Impact Factor
• Article: Cdc37/Hsp90 protein complex disruption triggers an autophagic clearance cascade for TDP-43 protein.

  Umesh K Jinwal, Jose F Abisambra, Juan Zhang, Sheetal Dharia, John C O'Leary, Tina Patel, Kaitlyn Braswell, Twisha Jani, Jason E Gestwicki, Chad A Dickey
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  ABSTRACT: The RNA-binding protein, trans-active response DNA-binding protein 43 (TDP-43), is normally found in the nucleus, but in amyotrophic lateral sclerosis, frontal temporal dementia, and some cases of Alzheimer disease it is cleaved and mislocalized to the cytosol, leading to accumulation. The mechanisms contributing to this are largely unknown. Here, we show that part of the normal clearance cascade for TDP-43 involves the Cdc37/Hsp90 complex. An Hsp90 inhibitor that disrupts the Cdc37/Hsp90 complex reduced TDP-43 levels to a greater extent than a standard Hsp90 ATPase inhibitor. When Cdc37 was depleted, TDP-43 underwent proteolytic clearance that was dependent on nuclear retrotranslocation and autophagic uptake. Accumulation of the microtubule-associated protein tau prevented the clearance of cleaved TDP-43, but not its production. This caused cleaved TDP-43 to accumulate, a feature observed in the brain of persons with Alzheimer disease. Clearance of cleaved TDP-43 was also prevented by knockdown of the autophagic inducer beclin1. Thus, in cells where TDP-43 clearance is normally needed, a system that employs manipulation of the Hsp90 complex and autophagy exists. But when tau accumulation is occurring, cleaved TDP-43 can no longer be cleared, perhaps explaining the emergence of these co-pathologies.
  Journal of Biological Chemistry 06/2012; 287(29):24814-20. · 4.77 Impact Factor
• Article: The three cornerstones of chemical biology: innovative probes, new discoveries, and enabling tools.

  Andrea D Thompson, Leah N Makley, Kathryn McMenimen, Jason E Gestwicki
  ACS Chemical Biology 05/2012; 7(5):791-6. · 6.45 Impact Factor
• Article: Allostery in the Hsp70 Chaperone Proteins.

  Erik R P Zuiderweg, Eric B Bertelsen, Aikaterini Rousaki, Matthias P Mayer, Jason E Gestwicki, Atta Ahmad
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  ABSTRACT: Heat shock 70-kDa (Hsp70) chaperones are essential to in vivo protein folding, protein transport, and protein re-folding. They carry out these activities using repeated cycles of binding and release of client proteins. This process is under allosteric control of nucleotide binding and hydrolysis. X-ray crystallography, NMR spectroscopy, and other biophysical techniques have contributed much to the understanding of the allosteric mechanism linking these activities and the effect of co-chaperones on this mechanism. In this chapter these findings are critically reviewed. Studies on the allosteric mechanisms of Hsp70 have gained enhanced urgency, as recent studies have implicated this chaperone as a potential drug target in diseases such as Alzheimer's and cancer. Recent approaches to combat these diseases through interference with the Hsp70 allosteric mechanism are discussed.
  Topics in current chemistry 05/2012; · 4.29 Impact Factor
• Article: Methylthioninium chloride (methylene blue) induces autophagy and attenuates tauopathy in vitro and in vivo.

  Erin E Congdon, Jessica W Wu, Natura Myeku, Yvette H Figueroa, Mathieu Herman, Paul S Marinec, Jason E Gestwicki, Chad A Dickey, W Haung Yu, Karen E Duff
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  ABSTRACT: More than 30 neurodegenerative diseases including Alzheimer disease (AD), frontotemporal lobe dementia (FTD), and some forms of Parkinson disease (PD) are characterized by the accumulation of an aggregated form of the microtubule-binding protein tau in neurites and as intracellular lesions called neurofibrillary tangles. Diseases with abnormal tau as part of the pathology are collectively known as the tauopathies. Methylthioninium chloride, also known as methylene blue (MB), has been shown to reduce tau levels in vitro and in vivo and several different mechanisms of action have been proposed. Herein we demonstrate that autophagy is a novel mechanism by which MB can reduce tau levels. Incubation with nanomolar concentrations of MB was sufficient to significantly reduce levels of tau both in organotypic brain slice cultures from a mouse model of FTD, and in cell models. Concomitantly, MB treatment altered the levels of LC3-II, cathepsin D, BECN1, and p62 suggesting that it was a potent inducer of autophagy. Further analysis of the signaling pathways induced by MB suggested a mode of action similar to rapamycin. Results were recapitulated in a transgenic mouse model of tauopathy administered MB orally at three different doses for two weeks. These data support the use of this drug as a therapeutic agent in neurodegenerative diseases.
  Autophagy 04/2012; 8(4):609-22. · 7.45 Impact Factor
• Source

  Available from: PubMed Central

  Article: Rhodacyanine derivative selectively targets cancer cells and overcomes tamoxifen resistance.

  John Koren, Yoshinari Miyata, Janine Kiray, John C O'Leary, Lana Nguyen, Jianping Guo, Laura J Blair, Xiokai Li, Umesh K Jinwal, Jin Q Cheng, Jason E Gestwicki, Chad A Dickey
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  ABSTRACT: MKT-077, a rhodacyanine dye, was shown to produce cancer specific cell death. However, complications prevented the use of this compound beyond clinical trials. Here we describe YM-1, a derivative of MKT-077. We found that YM-1 was more cytotoxic and localized differently than MKT-077. YM-1 demonstrated this cytotoxicity across multiple cancer cell lines. This toxicity was limited to cancer cell lines; immortalized cell models were unaffected. Brief applications of YM-1 were found to be non-toxic. Brief treatment with YM-1 restored tamoxifen sensitivity to a refractory tamoxifen-resistant MCF7 cell model. This effect is potentially due to altered estrogen receptor alpha phosphorylation, an outcome precipitated by selective reductions in Akt levels (Akt/PKB). Thus, modifications to the rhodocyanine scaffold could potentially be made to improve efficacy and pharmacokinetic properties. Moreover, the impact on tamoxifen sensitivity could be a new utility for this compound family.
  PLoS ONE 01/2012; 7(4):e35566. · 4.09 Impact Factor
• Article: Correction: Rhodacyanine Derivative Selectively Targets Cancer Cells and Overcomes Tamoxifen Resistance.

  John Koren, Yoshinari Miyata, Janine Kiray, John C O'Leary, Lana Nguyen, Jianping Guo, Laura J Blair, Xiaokai Li, Umesh K Jinwal, Jin Q Cheng, Jason E Gestwicki, Chad A Dickey
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  ABSTRACT: [This corrects the article on p. e35566 in vol. 7.].
  PLoS ONE 01/2012; 7(7). · 4.09 Impact Factor
• Article: Features of protein-protein interactions that translate into potent inhibitors: topology, surface area and affinity.

  Matthew C Smith, Jason E Gestwicki
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  ABSTRACT: Protein-protein interactions (PPIs) control the assembly of multi-protein complexes and, thus, these contacts have enormous potential as drug targets. However, the field has produced a mix of both exciting success stories and frustrating challenges. Here, we review known examples and explore how the physical features of a PPI, such as its affinity, hotspots, off-rates, buried surface area and topology, might influence the chances of success in finding inhibitors. This analysis suggests that concise, tight binding PPIs are most amenable to inhibition. However, it is also clear that emerging technical methods are expanding the repertoire of 'druggable' protein contacts and increasing the odds against difficult targets. In particular, natural product-like compound libraries, high throughput screens specifically designed for PPIs and approaches that favour discovery of allosteric inhibitors appear to be attractive routes. The first group of PPI inhibitors has entered clinical trials, further motivating the need to understand the challenges and opportunities in pursuing these types of targets.
  Expert Reviews in Molecular Medicine 01/2012; 14:e16. · 7.14 Impact Factor