Monoclonal antibodies against human collagenase and stromelysin

Replication-associated activities of purified human papillomavirus type 11 E1 helicase

Replication of human papillomavirus type11 (HPV11) requires both the E1 and the E2 proteins. E1 is structurally and functionally similar to SV40 large T-antigen and is a DNA helicase/NTPase that binds to the origin of replication and initiates viral DNA replication. The biochemical characterization of HPV E1 is incompletely documented in the literature in part because of difficulties in expressing and purifying the protein. Herein, we report a method for the overexpression of full-length, untagged E1 (73.5 kDa) in baculovirus-infected Trichoplusia ni insect cells and the purification to homogeneity using a two-step procedure. The purified protein is a nonspecific NTPase that hydrolyzes ATP, dATP, UTP, or GTP equally well. Point mutations were made in the putative NTPase domain to verify that the activities observed were encoded by E1. Purified mutant D523N had negligible ATPase and helicase activities but retained DNA-binding activity. Sedimentation equilibrium ultracentrifugation and glycerol gradient centrifugation demonstrated that the wild-type protein is primarily a hexamer in its purified form. Secondary structure determination by circular dichroism revealed a large percentage of alpha-helical structure consistent with secondary structure predictions. These data define a fundamental set of biochemical and kinetic parameters for HPV E1 which are a critical prerequisite to future mechanistic studies of the enzyme.

Use of a PPAR gamma-specific monoclonal antibody to demonstrate thiazolidinediones induce PPAR gamma receptor expression in vitro

Troglitazone and rosiglitazone (BRL49653), members of the thiazolidinedione (TZD) class of antidiabetic drugs, are peroxisome proliferator-activated receptor gamma (PPARgamma) ligands that induce adipocyte differentiation and increase the expression of PPARgamma protein. Here, we report the characterization of a PPARgamma specific monoclonal antibody (MAb), PgammaA53.25, and its use to monitor PPARgamma expression in the noncommitted pluripotent murine mesenchymal stem cell line, C3H10T1/2, treated with TZDs. MAb PgammaA53.25 was raised against a region in the N-terminal domain of human PPARgamma shared by splice variants PPARgamma1 and PPARgamma2. It recognizes immunizing antigen in enzyme-linked immunoadsorbent assay (ELISA), and does not cross-react with the N-terminal domains of PPARalpha or PPARdelta. In Western blotting, PgammaA53.25 reacts with the immunizing antigen as well as distinct protein bands corresponding to the molecular weight of full length PPARgamma from C3H10T1/2 cells and rat tissue lysates. In fluorescent microscopy, PgammaA53.25 immunostains nuclei of C3H10T1/2 cells treated with PPARgamma ligands. The fluorescence intensity of the treated cells is TZD dose-dependent, and correlates with lipid accumulation consistent with adipogenesis. Based on these results, we propose that MAb PgammaA53.25 will be a useful tool for elucidating the role of PPARgamma in fatty acid metabolism and adipocyte differentiation.

Monitoring of PPAR alpha protein expression in human tissue by the use of PPAR alpha-specific MAbs

We report the production and characterization of two PPAR alpha subtype-specific monoclonal antibodies raised against the N-terminal domain of PPAR alpha. P alpha b 11.80A is a Western-reactive antibody, whereas P alpha b 32.51 is useful for immunohistochemistry. Both antibodies exhibited high affinity against the immunogen based on BIAcore analysis, recognized full-length PPAR alpha protein in PPAR alpha-transfected CV-1 cells, and displayed no cross-reactivity against the N-terminal domains of PPAR gamma or PPAR delta proteins as demonstrated by various immunoassays. The application of these antibodies to a panel of normal human tissues revealed that PPAR alpha protein expression is highest in skeletal muscle, liver, and kidney, consistent with previously reported mRNA expression data. These antibodies provide us with valuable tools to further explore the function of PPAR alpha.

Neutralizing IGF-1 monoclonal antibody with cross-species reactivity

We report the generation of a murine IGF-1 monoclonal antibody designated 35I17, which exhibits unique cross-species reactivity. The antibody recognizes recombinant human and rat IGF-1 in ELISA, Western blots, and in an 125I-recombinant human IGF-1 Scintillation Proximity Assay. In addition, 35I17 blocks cell proliferation induced by recombinant human and rat IGF-1, and inhibits cell proliferation induced by sera from human, rat, calf, dog, goat, or mouse. The antibody inhibits rat IGF-1 binding to IGF-1 receptors, and prevents IGF-1-stimulated receptor and IRS-1 phosphorylation in LISN C4 cells, an IGF-1 receptor-transfected cell line. The cross-species and neutralizing properties of 35I17 may be useful in in vitro and in vivo animal studies for elucidating the role of IGF-1 in cancer, rheumatoid arthritis, and other diseases.

Activation of the nuclear receptor LXR by oxysterols defines a new hormone response pathway

Accumulation of cholesterol causes both repression of genes controlling cholesterol biosynthesis and cellular uptake and induction of cholesterol 7alpha-hydroxylase, which leads to the removal of cholesterol by increased metabolism to bile acids. Here, we report that LXRalpha and LXRbeta, two orphan members of the nuclear receptor superfamily, are activated by 24(S), 25-epoxycholesterol and 24(S)-hydroxycholesterol at physiologic concentrations. In addition, we have identified an LXR response element in the promoter region of the rat cholesterol 7alpha-hydroxylase gene. Our data provide evidence for a new hormonal signaling pathway that activates transcription in response to oxysterols and suggest that LXRs play a critical role in the regulation of cholesterol homeostasis.