Life Sciences Commons^™

Crystal Structure Of Human Thymidylate Synthase: A Structural Mechanism For Guiding Substrates Into The Active Site, Celia Schiffer, Ian Clifton, V. Jo Davisson, Daniel Santi, Robert Stroud

Celia A. Schiffer

The crystal structure of human thymidylate synthase, a target for anti-cancer drugs, is determined to 3.0 A resolution and refined to a crystallographic residual of 17.8%. The structure implicates the enzyme in a mechanism for facilitating the docking of substrates into the active site. This mechanism involves a twist of approximately 180 degrees of the active site loop, pivoted around the neighboring residues 184 and 204, and implicates ordering of external, eukaryote specific loops along with the well-characterized closure of the active site upon substrate binding. The highly conserved, but eukaryote-specific insertion of twelve residues 90-101 (h117-128), and of eight …

Association Of A Novel Human Immunodeficiency Virus Type 1 Protease Substrate Cleft Mutation, L23i, With Protease Inhibitor Therapy And In Vitro Drug Resistance, Elizabeth Johnston, Mark Winters, Soo-Yon Rhee, Thomas Merigan, Celia Schiffer, Robert Shafer

Celia A. Schiffer

We observed a previously uncharacterized mutation in the protease substrate cleft, L23I, in 31 of 4,303 persons undergoing human immunodeficiency virus type 1 genotypic resistance testing. In combination with V82I, L23I was associated with a sevenfold reduction in nelfinavir susceptibility and a decrease in replication capacity. In combination with other drug resistance mutations, L23I was associated with multidrug resistance and a compensatory increase in replication capacity.

Substrate Shape Determines Specificity Of Recognition For Hiv-1 Protease: Analysis Of Crystal Structures Of Six Substrate Complexes, Moses Prabu-Jeyabalan, Ellen Nalivaika, Celia Schiffer

Celia A. Schiffer

The homodimeric HIV-1 protease is the target of some of the most effective antiviral AIDS therapy, as it facilitates viral maturation by cleaving ten asymmetric and nonhomologous sequences in the Gag and Pol polyproteins. Since the specificity of this enzyme is not easily determined from the sequences of these cleavage sites alone, we solved the crystal structures of complexes of an inactive variant (D25N) of HIV-1 protease with six peptides that correspond to the natural substrate cleavage sites. When the protease binds to its substrate and buries nearly 1000 A2 of surface area, the symmetry of the protease is broken, …

Insights Into Interferon Regulatory Factor Activation From The Crystal Structure Of Dimeric Irf5, Weijun Chen, Suvana Lam, Hema Srinath, Zhaozhao Jiang, John Correia, Celia Schiffer, Katherine Fitzgerald, Kai Lin, William Royer

Celia A. Schiffer

Interferon regulatory factors (IRFs) are essential in the innate immune response and other physiological processes. Activation of these proteins in the cytoplasm is triggered by phosphorylation of serine and threonine residues in a C-terminal autoinhibitory region, which stimulates dimerization, transport into the nucleus, assembly with the coactivator CBP/p300 and initiation of transcription. The crystal structure of the transactivation domain of pseudophosphorylated human IRF5 strikingly reveals a dimer in which the bulk of intersubunit interactions involve a highly extended C-terminal region. The corresponding region has previously been shown to block CBP/p300 binding to unphosphorylated IRF3. Mutation of key interface residues supports …

Toward The Design Of Mutation-Resistant Enzyme Inhibitors: Further Evaluation Of The Substrate Envelope Hypothesis, Visvaldas Kairys, Michael Gilson, Viney Lather, Celia Schiffer, Miguel Fernandes

Celia A. Schiffer

Previous studies have shown the usefulness of the substrate envelope concept in the analysis and prediction of drug resistance profiles for human immunodeficiency virus protease mutants. This study tests its applicability to several other therapeutic targets: Abl kinase, chitinase, thymidylate synthase, dihydrofolate reductase, and neuraminidase. For the targets where many (> or =6) mutation data are available to compute the average mutation sensitivity of inhibitors, the total volume of an inhibitor molecule that projects outside the substrate envelope V(out), is found to correlate with average mutation sensitivity. Analysis of a locally computed volume suggests that the same correlation would hold …

Design Of Hiv-1 Protease Inhibitors Active On Multidrug-Resistant Virus, Dominique Surleraux, Herman De Kock, Wim Verschueren, Geert Pille, Louis Maes, Anik Peeters, Sandrine Vendeville, Sandra De Meyer, Hilde Azijn, Rudi Pauwels, Marie-Pierre De Bethune, Nancy King, Moses Prabu-Jeyabalan, Celia Schiffer, Piet Wigerinck

Celia A. Schiffer

On the basis of structural data gathered during our ongoing HIV-1 protease inhibitors program, from which our clinical candidate TMC114 9 was selected, we have discovered new series of fused heteroaromatic sulfonamides. The further extension into the P2' region was aimed at identifying new classes of compounds with an improved broad spectrum activity and acceptable pharmacokinetic properties. Several of these compounds display an exceptional broad spectrum activity against a panel of highly cross-resistant mutants. Certain members of these series exhibit favorable pharmacokinetic profiles in rat and dog. Crystal structures and molecular modeling were used to rationalize the broad spectrum profile …

Pten Enters The Nucleus By Diffusion, Fenghua Liu, Stefan Wagner, Robert Campbell, Jeffrey Nickerson, Celia Schiffer, Alonzo Ross

Celia A. Schiffer

Despite much evidence for phosphatidylinositol phosphate (PIP)-triggered signaling pathways in the nucleus, there is little understanding of how the levels and activities of these proteins are regulated. As a first step to elucidating this problem, we determined whether phosphatase and tensin homolog deleted on chromosome 10 (PTEN) enters the nucleus by passive diffusion or active transport. We expressed various PTEN fusion proteins in tsBN2, HeLa, LNCaP, and U87MG cells and determined that the largest PTEN fusion proteins showed little or no nuclear localization. Because diffusion through nuclear pores is limited to proteins of 60,000 Da or less, this suggests that …

N88d Facilitates The Co-Occurrence Of D30n And L90m And The Development Of Multidrug Resistance In Hiv Type 1 Protease Following Nelfinavir Treatment Failure, Yumi Mitsuya, Mark Winters, W. Jeffrey Fessel, Soo-Yon Rhee, Leo Hurley, Michael Horberg, Celia Schiffer, Andrew Zolopa, Robert Shafer

Celia A. Schiffer

Nelfinavir was once one of the most commonly used protease inhibitors (PIs). To investigate the genetic mechanisms of multidrug resistance in protease isolates with the primary nelfinavir resistance mutation D30N, we analyzed patterns of protease mutations in 582 viruses with D30N from 460 persons undergoing HIV-1 genotypic resistance testing at Stanford University Hospital from 1997 to 2005. Three patterns of mutational associations were identified. First, D30N was positively associated with N88D but negatively associated with N88S. Second, D30N and L90M were negatively associated except in the presence of N88D, which facilitated the co-occurrence of D30N and L90M. Third, D30N+N88D+L90M formed …

Design And Synthesis Of Hiv-1 Protease Inhibitors Incorporating Oxazolidinones As P2/P2' Ligands In Pseudosymmetric Dipeptide Isosteres, G. S. Kiran Kumar Reddy, Akbar Ali, Madhavi Nalam, Saima Anjum, Hong Cao, Robin Nathans, Celia Schiffer, Tariq Rana

Celia A. Schiffer

A series of novel HIV-1 protease inhibitors based on two pseudosymmetric dipeptide isosteres have been synthesized and evaluated. The inhibitors were designed by incorporating N-phenyloxazolidinone-5-carboxamides into the hydroxyethylene and (hydroxyethyl)hydrazine dipeptide isosteres as P2 and P2' ligands. Compounds with (S)-phenyloxazolidinones attached at a position proximal to the central hydroxyl group showed low nM inhibitory activities against wild-type HIV-1 protease. Selected compounds were further evaluated for their inhibitory activities against a panel of multidrug-resistant protease variants and for their antiviral potencies in MT-4 cells. The crystal structures of lopinavir (LPV) and two new inhibitors containing phenyloxazolidinone-based ligands in complex with wild-type …

Structure Of A Phage Display-Derived Variant Of Human Growth Hormone Complexed To Two Copies Of The Extracellular Domain Of Its Receptor: Evidence For Strong Structural Coupling Between Receptor Binding Sites, Celia Schiffer, Mark Ultsch, Scott Walsh, William Somers, Abraham De Vos, Anthony Kossiakoff

Celia A. Schiffer

The structure of the ternary complex between the phage display- optimized, high-affinity Site 1 variant of human growth hormone (hGH) and two copies of the extracellular domain (ECD) of the hGH receptor (hGHR) has been determined at 2.6 A resolution. There are widespread and significant structural differences compared to the wild-type ternary hGH hGHR complex. The hGH variant (hGH(v)) contains 15 Site 1 mutations and binds>10(2) tighter to the hGHR ECD (hGH(R1)) at Site 1. It is biologically active and specific to hGHR. The hGH(v) Site 1 interface is somewhat smaller and 20% more hydrophobic compared to the wild-type …

Replacement Of The P1 Amino Acid Of Human Immunodeficiency Virus Type 1 Gag Processing Sites Can Inhibit Or Enhance The Rate Of Cleavage By The Viral Protease, Steve Pettit, Gavin Henderson, Celia Schiffer, Ronald Swanstrom

Celia A. Schiffer

Processing of the human immunodeficiency virus type 1 (HIV-1) Gag precursor is highly regulated, with differential rates of cleavage at the five major processing sites to give characteristic processing intermediates. We examined the role of the P1 amino acid in determining the rate of cleavage at each of these five sites by using libraries of mutants generated by site-directed mutagenesis. Between 12 and 17 substitution mutants were tested at each P1 position in Gag, using recombinant HIV-1 protease (PR) in an in vitro processing reaction of radiolabeled Gag substrate. There were three sites in Gag (MA/CA, CA/p2, NC/p1) where one …

Crystallization Of Human Thymidylate Synthase, Celia Schiffer, V. Jo Davisson, Daniel Santi, Robert Stroud

Celia A. Schiffer

Human thymidylate synthase has been crystallized in the absence of ligands and diffracts beyond 3.0 A. The protein was cloned and expressed in Escherichia coli and then crystallized from ammonium sulfate in the presence of beta-mercaptoethanol at a variety of pH values. The crystals are trigonal in the space-group P3(1)21; the unit cell dimensions are a = b = 96.7 A, c = 84.1 A.

Human Immunodeficiency Virus Type 1 Protease-Correlated Cleavage Site Mutations Enhance Inhibitor Resistance, Madhavi Kolli, Eric Stawiski, Colombe Chappey, Celia Schiffer

Celia A. Schiffer

Drug resistance is an important cause of antiretroviral therapy failure in human immunodeficiency virus (HIV)-infected patients. Mutations in the protease render the virus resistant to protease inhibitors (PIs). Gag cleavage sites also mutate, sometimes correlating with resistance mutations in the protease, but their contribution to resistance has not been systematically analyzed. The present study examines mutations in Gag cleavage sites that associate with protease mutations and the impact of these associations on drug susceptibilities. Significant associations were observed between mutations in the nucleocapsid-p1 (NC-p1) and p1-p6 cleavage sites and various PI resistance-associated mutations in the protease. Several patterns were frequently …

Discovery And Selection Of Tmc114, A Next Generation Hiv-1 Protease Inhibitor, Dominique Surleraux, Abdellah Tahri, Wim Verschueren, Geert Pille, Herman De Kock, Tim Jonckers, Anik Peeters, Sandra De Meyer, Hilde Azijn, Rudi Pauwels, Marie-Pierre De Bethune, Nancy King, Moses Prabu-Jeyabalan, Celia Schiffer, Piet Wigerinck

Celia A. Schiffer

The screening of known HIV-1 protease inhibitors against a panel of multi-drug-resistant viruses revealed the potent activity of TMC126 on drug-resistant mutants. In comparison to amprenavir, the improved affinity of TMC126 is largely the result of one extra hydrogen bond to the backbone of the protein in the P2 pocket. Modification of the substitution pattern on the phenylsulfonamide P2' substituent of TMC126 created an interesting SAR, with the close analogue TMC114 being found to have a similar antiviral activity against the mutant and the wild-type viruses. X-ray and thermodynamic studies on both wild-type and mutant enzymes showed an extremely high …

Specific Thiazolidinediones Inhibit Ovarian Cancer Cell Line Proliferation And Cause Cell Cycle Arrest In A Pparγ Independent Manner, Linah Al-Alem, R. Chase Southard, Michael W. Kilgore, Thomas E. Curry

Pharmacology and Nutritional Sciences Faculty Publications

BACKGROUND: Peroxisome Proliferator Activated Receptor gamma (PPARγ) agonists, such as the thiazolinediones (TZDs), have been studied for their potential use as cancer therapeutic agents. We investigated the effect of four TZDs--Rosiglitazone (Rosi), Ciglitazone (CGZ), Troglitazone (TGZ), and Pioglitazone (Pio)--on ovarian cancer cell proliferation, PPARγ expression and PPAR luciferase reporter activity. We explored whether TZDs act in a PPARγ dependent or independent manner by utilizing molecular approaches to inhibit or overexpress PPARγ activity.

PRINCIPAL FINDINGS: Treatment with CGZ or TGZ for 24 hours decreased proliferation in three ovarian cancer cell lines, Ovcar3, CaOv3, and Skov3, whereas Rosi and Pio had no …