Browsing by Author "Stein, Ross L."

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Designed inhibitors of insulin-degrading enzyme regulate the catabolism and activity of insulin
(PLoS ONE, 5/7/2010) Leissring, Malcolm A.; Malito, Enrico; Hedouin, Sabrine; Reinstatler, Lael; Sahara, Tomoko; Abdul-Hay, Samer O.; Choudhry, Shakeel; Maharvi, Ghulam M.; Fauq, Abdul H.; Huzarska, Malwina A.; May, Philip S.; Choi, Sungwoon; Logan, Todd P.; Turk, Benjamin E.; Cantley, Lewis C.; Manolopoulou, Marika; Tang, Wei-Jen; Stein, Ross L.; Cuny, Gregory D.; Selkoe, Dennis J.
Background- Insulin is a vital peptide hormone that is a central regulator of glucose homeostasis, and impairments in insulin signaling cause diabetes mellitus. In principle, it should be possible to enhance the activity of insulin by inhibiting its catabolism, which is mediated primarily by insulin-degrading enzyme (IDE), a structurally and evolutionarily distinctive zinc-metalloprotease. Despite interest in pharmacological inhibition of IDE as an attractive anti-diabetic approach dating to the 1950s, potent and selective inhibitors of IDE have not yet emerged. Methodology/Principal Findings- We used a rational design approach based on analysis of combinatorial peptide mixtures and focused compound libraries to develop novel peptide hydroxamic acid inhibitors of IDE. The resulting compounds are ?106 times more potent than existing inhibitors, non-toxic, and surprisingly selective for IDE vis-à-vis conventional zinc-metalloproteases. Crystallographic analysis of an IDE-inhibitor complex reveals a novel mode of inhibition based on stabilization of IDE's “closed,” inactive conformation. We show further that pharmacological inhibition of IDE potentiates insulin signaling by a mechanism involving reduced catabolism of internalized insulin. Conclusions/Significance The inhibitors we describe are the first to potently and selectively inhibit IDE or indeed any member of this atypical zinc-metalloprotease superfamily. The distinctive structure of IDE's active site, and the mode of action of our inhibitors, suggests that it may be possible to develop inhibitors that cross-react minimally with conventional zinc-metalloproteases. Significantly, our results reveal that insulin signaling is normally regulated by IDE activity not only extracellularly but also within cells, supporting the longstanding view that IDE inhibitors could hold therapeutic value for the treatment of diabetes.
Development of a mechanism-based high-throughput screen assay for leucine-rich repeat kinase 2—Discovery of LRRK2 inhibitors
(Analytical Biochemistry, 2011-19-15) Liu, Min; Poulose, Shibu; Schuman, Eli; Zaitsev, Alexandra D.; Dobson, Brittany C.; Auerbach, Ken; Seyb, Kathleen I.; Cuny, Gregory D.; Glicksman, Marcie A.; Stein, Ross L.; Yue, Zhenyu
LRRK2 is a large and complex protein that possesses kinase and GTPase activities and has emerged as the most relevant player in PD pathogenesis possibly through a toxic gain-of-function mechanism. Kinase activity is a critical component of LRRK2 function and represents a viable target for drug discovery. We now report the development of a mechanism-based TR-FRET assay for the LRRK2 kinase activity using full-length LRRK2. In this assay, PLK-peptide was chosen as the phosphoryl acceptor. A combination of steady-state kinetic studies and computer simulations was used to calculate the initial concentrations of ATP and PLK-peptide to generate a steady-state situation that favors the identification of ATP noncompetitive inhibitors. The assay was also run in the absence of GTP. Under these conditions, the assay was sensitive to inhibitors that directly interact with the kinase domain and those that modulate the kinase activity by directly interacting with other domains including the GTPase domain. The assay was optimized and used to robustly evaluate our compound library in a 384-well format. An inhibitor identified through the screen was further characterized as a noncompetitive inhibitor with both ATP and PLK-peptide and showed similar inhibition against LRRK2 WT and the mutant G2019S.
Identification of Small Molecule Inhibitors of the Mitotic Kinase Haspin by High-Throughput Screening Using a Homogeneous Time-Resolved Fluorescence Resonance Energy Transfer Assay
(Journal of Biomolecular Screening, 2009-12) Patnaik, Debasis; Xian, Jun; Glicksman, Marcie A.; Cuny, Gregory D.; Stein, Ross L.; Higgins, Jonathan M.G.
Haspin/Gsg2 is a kinase that phosphorylates histone H3 at Thr-3 (H3T3ph) during mitosis. Its depletion by RNA interference results in failure of chromosome alignment and a block in mitosis. Haspin, therefore, is a novel target for development of antimitotic agents. We report the development of a high-throughput time-resolved fluorescence resonance energy transfer (TR-FRET) kinase assay for haspin. Histone H3 peptide was used as a substrate, and a europium-labeled H3T3ph phosphospecific monoclonal antibody was used to detect phosphorylation. A library of 137632 small molecules was screened at Km concentrations of ATP and peptide to allow identification of diverse inhibitor types. Reconfirmation of hits and IC 50 determinations were carried out with the TR-FRET assay and by a radiometric assay using recombinant histone H3 as the substrate. A preliminary assessment of specificity was made by testing inhibition of 2 unrelated kinases. EC 50 values in cells were determined using a cell-based ELISA of H3T3ph. Five compounds were selected as leads based on potency and chemical structure considerations. These leads form the basis for the development of specific inhibitors of haspin that will have clear utility in basic research and possible use as starting points for development of antimitotic anticancer therapeutics
Small-Molecule Activators of Insulin-Degrading Enzyme Discovered through High-Throughput Compound Screening
(PLoS ONE, 4/22/2009) Cabrol, Christelle; Huzarska, Malwina A.; Dinolfo, Christopher; Rodriguez, Maria C.; Reinstatler, Lael; Ni, Jake; Yeh, Li-An; Cuny, Gregory D.; Stein, Ross L.; Selkoe, Dennis J.; Leissring, Malcolm A.
Background-Hypocatabolism of the amyloid ?-protein (A?) by insulin-degrading enzyme (IDE) is implicated in the pathogenesis of Alzheimer disease (AD), making pharmacological activation of IDE an attractive therapeutic strategy. However, it has not been established whether the proteolytic activity of IDE can be enhanced by drug-like compounds. Methodology/Principal Findings- Based on the finding that ATP and other nucleotide polyphosphates modulate IDE activity at physiological concentrations, we conducted parallel high-throughput screening campaigns in the absence or presence of ATP and identified two compounds—designated Ia1 and Ia2—that significantly stimulate IDE proteolytic activity. Both compounds were found to interfere with the crosslinking of a photoaffinity ATP analogue to IDE, suggesting that they interact with a bona fide ATP-binding domain within IDE. Unexpectedly, we observed highly synergistic activation effects when the activity of Ia1 or Ia2 was tested in the presence of ATP, a finding that has implications for the mechanisms underlying ATP-mediated activation of IDE. Notably, Ia1 and Ia2 activated the degradation of A? by ?700% and ?400%, respectively, albeit only when A? was presented in a mixture also containing shorter substrates. Conclusions/Significance-This study describes the first examples of synthetic small-molecule activators of IDE, showing that pharmacological activation of this important protease with drug-like compounds is achievable. These novel activators help to establish the putative ATP-binding domain as a key modulator of IDE proteolytic activity and offer new insights into the modulatory action of ATP. Several larger lessons abstracted from this screen will help inform the design of future screening campaigns and facilitate the eventual development of IDE activators with therapeutic utility.
Small-molecule inhibitors of phosphatidylcholine transfer protein/StarD2 identified by high-throughput screening
(Analytical Biochemistry, 2009-12) Wagle, Neil; Xian, Jun; Shishova, Ekaterina Y.; Wei, Jie; Glicksman, Marcie A.; Cuny, Gregory D.; Stein, Ross L.; Cohen, David E.
Phosphatidylcholine transfer protein (PC–TP, also referred to as StarD2) is a highly specific intracellular lipid-binding protein that catalyzes the transfer of phosphatidylcholines between membranes in vitro. Recent studies have suggested that PC–TP in vivo functions to regulate fatty acid and glucose metabolism, possibly via interactions with selected other proteins. To begin to address the relationship between activity in vitro and biological function, we undertook a high-throughput screen to identify small-molecule inhibitors of the phosphatidylcholine transfer activity of PC–TP. After adapting a fluorescence quench assay to measure phosphatidylcholine transfer activity, we screened 114,752 compounds of a small-molecule library. The high-throughput screen identified 14 potential PC–TP inhibitors. Of these, 6 compounds exhibited characteristics consistent with specific inhibition of PC–TP activity, with IC50 values that ranged from 4.1 to 95.0 ?M under conditions of the in vitro assay. These compounds should serve as valuable reagents to elucidate the biological function of PC–TP. Because mice with homozygous disruption of the PC–TP gene (Pctp) are sensitized to insulin action and relatively resistant to the development of atherosclerosis, these inhibitors may also prove to be of value in the management of diabetes and atherosclerotic cardiovascular diseases.
Structure–activity relationship study of acridine analogs as haspin and DYRK2 kinase inhibitors
(Bioorganic and Medicinal Chemistry Letters, 6/15/2011) Cuny, Gregory D.; Robin, Maxime; Ulyanova, Natalia P.; Patnaik, Debasis; Pique, Valerie; Casano, Gilles; Liu, Ji-Feng; Lin, Xiangjie; Xian, Jun; Glicksman, Marcie A.; Stein, Ross L.; Higgins, Jonathan M.G.
Haspin is a serine/threonine kinase required for completion of normal mitosis that is highly expressed during cell proliferation, including in a number of neoplasms. Consequently, it has emerged as a potential therapeutic target in oncology. A high throughput screen of approximately 140,000 compounds identified an acridine analog as a potent haspin kinase inhibitor. Profiling against a panel of 270 kinases revealed that the compound also exhibited potent inhibitory activity for DYRK2, another serine/threonine kinase. An optimization study of the acridine series revealed that the structure–activity relationship (SAR) of the acridine series for haspin and DYRK2 inhibition had many similarities. However, several structural differences were noted that allowed generation of a potent haspin kinase inhibitor (33, IC50 <60 nM) with 180-fold selectivity over DYRK2. In addition, a moderately potent DYRK2 inhibitor (41, IC50 <400 nM) with a 5.4-fold selectivity over haspin was also identified.
Structure–activity relationship study of beta-carboline derivatives as haspin kinase inhibitors
(Bioorganic and Medicinal Chemistry Letters, 2013-03) Cuny, Gregory D.; Ulyanova, Natalia P.; Patnaik, Debasis; Liu, Ji-Feng; Lin, Xiangjie; Auerbach, Ken; Ray, Soumya S.; Xian, Jun; Glicksman, Marcie A.; Stein, Ross L.; Higgins, Jonathan M.G.
Haspin is a serine/threonine kinase that phosphorylates Thr-3 of histone H3 in mitosis that has emerged as a possible cancer therapeutic target. High throughput screening of approximately 140,000 compounds identified the beta-carbolines harmine and harmol as moderately potent haspin kinase inhibitors. Based on information obtained from a structure–activity relationship study previously conducted for an acridine series of haspin inhibitors in conjunction with in silico docking using a recently disclosed crystal structure of the kinase, harmine analogs were designed that resulted in significantly increased haspin kinase inhibitory potency. The harmine derivatives also demonstrated less activity towards DYRK2 compared to the acridine series. In vitro mouse liver microsome stability and kinase profiling of a representative member of the harmine series (42, LDN-211898) are also presented.
Structure–activity relationship study of EphB3 receptor tyrosine kinase inhibitors
(Bioorganic and Medicinal Chemistry Letters, 2010-11) Qiao, Lixin; Choi, Sungwoon; Case, April; Gainer, Thomas G.; Seyb, Kathleen I.; Glicksman, Marcie A.; Lo, Donald, C.; Stein, Ross L.; Cuny, Gregory D.
A structure–activity relationship study for a 2-chloroanilide derivative of pyrazolo[1,5-a]pyridine revealed that increased EphB3 kinase inhibitory activity could be accomplished by retaining the 2-chloroanilide and introducing a phenyl or small electron donating substituents to the 5-position of the pyrazolo[1,5-a]pyridine. In addition, replacement of the pyrazolo[1,5-a]pyridine with imidazo[1,2-a]pyridine was well tolerated and resulted in enhanced mouse liver microsome stability. The structure–activity relationship for EphB3 inhibition of both heterocyclic series was similar. Kinase inhibitory activity was also demonstrated for representative analogs in cell culture. An analog (32, LDN-211904) was also profiled for inhibitory activity against a panel of 288 kinases and found to be quite selective for tyrosine kinases. Overall, these studies provide useful molecular probes for examining the in vitro, cellular and potentially in vivo kinase-dependent function of EphB3 receptor.