Generation of an LFA-1 antagonist by the transfer of the ICAM-1 immunoregulatory epitope to a small molecule.

The protein-protein interaction between leukocyte functional antigen-1 (LFA-1) and intercellular adhesion molecule-1 (ICAM-1) is critical to lymphocyte and immune system function. Here, we report on the transfer of the contiguous, nonlinear epitope of ICAM-1, responsible for its association with LFA-1, to a small-molecule framework. These LFA-1 antagonists bound LFA-1, blocked binding of ICAM-1, and inhibited a mixed lymphocyte reaction (MLR) with potency significantly greater than that of cyclosporine A. Furthermore, in comparison to an antibody to LFA-1, they exhibited significant anti-inflammatory effects in vivo. These results demonstrate the utility of small-molecule mimics of nonlinear protein epitopes and the protein epitopes themselves as leads in the identification of novel pharmaceutical agents.

Transfer of a protein binding epitope to a minimal designed peptide.

Results from protein mutagenesis and x-ray crystallographic studies of the multidomain protein Vascular Cell Adhesion Molecule (VCAM) were used to design cyclic octapeptides that retain the critical structural and binding elements of the epitope of VCAM in the interaction with the integrin alpha 4 beta 1 (VLA-4). Changes in the activities of peptide analogues correlated with the relative activities of protein mutants of VCAM, and predicted the properties of two new mutants that bound alpha 4 beta 1 with improved affinity vs wild type protein. The nmr structures of two peptides revealed a high degree of similarity to the structure of the VCAM binding epitope. These results demonstrate that a compact binding epitope identified via protein structure-function studies may be transferred to a synthetically accessible small peptide with the key structure-activity relationships intact.

Alpha-subunit of farnesyltransferase is phosphorylated in vivo: effect of protein phosphatase-1 on enzymatic activity.

Farnesyltransferase is a heterodimer consisting of a 49 kDa alpha-subunit and a 46 kDa beta-subunit. In this report, we demonstrate that the endogenous heterodimeric farnesyltransferase protein is phosphorylated at the alpha-subunit in vivo and phosphorylation plays a role in the regulation of farnesyltransferase activity. In vivo 32P-labeling of PC-12 cells followed by immunoprecipitation with specific anti rat alpha-subunit IgG showed a labeled alpha-subunit protein band at an expected molecular mass of 49 kDa. Treatment of PC-12 cells with protein phosphatase inhibitor, Calyculin A, resulted in a decrease in FTase activity, and phophoserine/phosphothreonine-specific protein phosphatase-1 treatment of PC-12 and GM37 cell extracts resulted in 100% and 375% increase in farnesyltransferase activity, respectively, compared to untreated extracts.

Evaluation of EMIT Cyclosporine Assay for use with whole blood.

We evaluated the EMIT Cyclosporine Assay, designed for specific quantification of cyclosporine (CsA) in whole blood. The assay was run on the Roche Cobas Mira or Cobas Mira S analyzer. Analytical recovery from both normal donor whole blood and transplant patients' samples was within 17% of the standards. Measurement of diluted out-of-range samples also yielded excellent recovery (101-105%). Within-run, between-run, and total CVs were < or = 8.1%, 10.9%, and 12.1%, respectively. The detection limit was < 32 micrograms/L. The assay was linear from 0 to 500 micrograms/L. No significant cross-reactivity was observed for CsA metabolites AM1, AM19, and AM4N. Slight cross-reactivity occurred with metabolite AM9; 670 micrograms/L AM9 increased the measured CsA concentration by 49 micrograms/L. High concentrations of bilirubin, uric acid, triglycerides, and cholesterol, as well as 54 commonly coadministered drugs did not interfere with CsA quantification. Similarly, neither extreme values of hematocrit nor choice of anticoagulant affected CsA recovery. Sample extract stability was > 4 h, and assay calibration was stable for at least 2 weeks. Patients' samples analyzed by the EMIT assay showed strong correlation with both HPLC and 125I-RIA (r > 0.97). We conclude that the EMIT Cyclosporine Assay provides a convenient, accurate, and precise method for specific quantification of CsA in whole blood.

Synergistic induction of polypeptides by tumor necrosis factor and interferon-gamma in cells sensitive or resistant to tumor necrosis factor: assessment by computer based analysis of two-dimensional gels using the PDQUEST system.

Tumor necrosis factor (TNF) synergistically enhanced the antiproliferative activity of interferon-gamma (IFN-gamma) in both TNF-sensitive and TNF-resistant variants of the cervical carcinoma line, ME-180. TNF alone had no apparent effect on the levels of synthesis of individual proteins in either of these variant cell lines as assessed by computerized two-dimensional gel analysis of cell lysates using the PDQUEST system. However, IFN-gamma enhanced the levels of 18 polypeptides and suppressed the levels of 10 polypeptides in both cell lines. When used in combination in both cell lines, TNF and IFN-gamma induced the synthesis of 10 polypeptides that were not induced by either agent alone. These synergistically induced polypeptides may be crucial to the mechanism of the synergistic antiproliferative action of TNF and IFN-gamma in ME-180 cells.

Overlapping polypeptide induction in human fibroblasts in response to treatment with interferon-alpha, interferon-gamma, interleukin 1 alpha, interleukin 1 beta, and tumor necrosis factor.

Cytokine-induced polypeptides were identified in whole cell lysates of human fibroblasts by computer-based analysis of two-dimensional gels with the use of the PDQuest System. Treatment with interferon-alpha (IFN-alpha) and interferon-gamma (IFN-gamma) enhanced the synthesis of 12 and 28 polypeptides, respectively. Exposure to interleukin 1 alpha (IL-1 alpha) or interleukin 1 beta (IL-1 beta) resulted in the increased synthesis of seven identical polypeptides. Treatment with tumor necrosis factor (TNF) at 100 U/ml led to enhanced expression of seven polypeptides, whereas exposure to TNF at 1000 U/ml increased the levels of these seven plus two additional polypeptides. The antiviral and antiproliferative effects of these cytokines in strain 153 fibroblasts were also assessed. Both IFN-alpha and IFN-gamma exhibited antiviral activity, whereas both IL-1 and TNF stimulated fibroblast growth. IFN-gamma was alone in inhibiting proliferation. Thus, although these cytokines exhibit low degrees of structural homology, they share some common functions, and a number of polypeptides were induced in common by two or more of these agents. The greatest similarities in polypeptide induction occur between IFN-alpha and IFN-gamma and between the IL-1s and TNF. However, polypeptides were also induced in common by IFN-alpha and TNF, IFN-gamma and IL-1, and IFN-gamma and TNF. These similarities in polypeptide induction may reflect the overlapping functions of these cytokines and may be indicative of common biochemical pathways in their mechanisms of action.