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J Stebbins

Publications and source records attributed to J Stebbins.

15 recordsLinked to original sources
PubMed2006

Regulation of Nur77 nuclear export by c-Jun N-terminal kinase and Akt.

Proapoptotic nuclear receptor family member Nur77 translocates from the nucleus to the mitochondria, where it interacts with Bcl-2 to trigger apoptosis. Nur77 translocation is induced by certain apoptotic stimuli, including the synthetic retinoid-related 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalenecarboxylic acid (AHPN)/CD437 class. In this study, we investigated the molecular mechanism by which AHPN/CD437 analog (E)-4-[3-(1-adamantyl)-4-hydroxyphenyl]-3-chlorocinnamic acid (3-Cl-AHPC) induces Nur77 nuclear export. Our results demonstrate that 3-Cl-AHPC effectively activated Jun N-terminal kinase (JNK), which phosphorylates Nur77. Inhibition of JNK activation by a JNK inhibitor suppressed 3-Cl-AHPC-induced Nur77 nuclear export and apoptosis. In addition, several JNK upstream activators, including the phorbol ester TPA, anisomycin and MAPK kinase kinase-1 (MEKK1), phosphorylated Nur77 and induced its nuclear export. However, Nur77 phosphorylation by JNK, although essential, was not sufficient for inducing Nur77 nuclear export. Induction of Nur77 nuclear export by MEKK1 required a prolonged MEKK1 activation and was attenuated by Akt activation. Expression of constitutively active Akt prevented MEKK1-induced Nur77 nuclear export. Conversely, transfection of dominant-negative Akt or treatment with a phosphatidylinositol 3-kinase (PI3-K) inhibitor accelerated MEKK1-induced Nur77 nuclear export. Furthermore, mutation of an Akt phosphorylation residue Ser351 in Nur77 abolished the effect of Akt or the PI3-K inhibitor. Together, our results demonstrate that both activation of JNK and inhibition of Akt play a role in translocation of Nur77 from the nucleus to the cytoplasm.

Adamantane↗
PubMed2006

Repeatability of a model for measuring multi-segment foot kinematics in children.

This study used a previously tested foot model and adapted it for use with children. A number of variations on this adapted model were implemented and tested for repeatability and accuracy on 15 healthy children on three occasions. These included redefinition of the long axes of the tibia and forefoot, assessment of the flexibility of the forefoot and evaluation of the variability of the wand marker on the heel for both static and dynamic trials. It was found that variations on the model produced only minimal changes in repeatability, the only significant change being elimination of the wand marker on the heel in the static trial, which reduced between-day variability of hindfoot motion in the transverse plane. However, some differences were evident in the mean values for all variations. Based on these results, the most accurate and appropriate version of the model is proposed, and average kinematic curves are presented based on the measurements from 14 healthy children.

Adolescent↗
PubMed2000

The silencing protein SIR2 and its homologs are NAD-dependent protein deacetylases.

Homologs of the chromatin-bound yeast silent information regulator 2 (SIR2) protein are found in organisms from all biological kingdoms. SIR2 itself was originally discovered to influence mating-type control in haploid cells by locus-specific transcriptional silencing. Since then, SIR2 and its homologs have been suggested to play additional roles in suppression of recombination, chromosomal stability, metabolic regulation, meiosis, and aging. Considering the far-ranging nature of these functions, a major experimental goal has been to understand the molecular mechanism(s) by which this family of proteins acts. We report here that members of the SIR2 family catalyze an NAD-nicotinamide exchange reaction that requires the presence of acetylated lysines such as those found in the N termini of histones. Significantly, these enzymes also catalyze histone deacetylation in a reaction that absolutely requires NAD, thereby distinguishing them from previously characterized deacetylases. The enzymes are active on histone substrates that have been acetylated by both chromatin assembly-linked and transcription-related acetyltransferases. Contrary to a recent report, we find no evidence that these proteins ADP-ribosylate histones. Discovery of an intrinsic deacetylation activity for the conserved SIR2 family provides a mechanism for modifying histones and other proteins to regulate transcription and diverse biological processes.

Acetylation↗
PubMed1997

A microtiter colorimetric assay for the HIV-1 protease.

We have developed a novel colorimetric assay for the HIV-1 protease that is suitable for high-throughput screening of inhibitors. This assay utilizes two nonenzymatic reaction steps, which are carried out in succession following enzymatic hydrolysis of a synthetic peptide. The first step involves a carbamylation reaction between cyanate and the nascent alpha amino group resulting from enzymatic hydrolysis. The second step involves a carbamidodiacetyl reaction between 2,3-butanedione monoxime (diacetylmonoxime) and the de novo carbamido compound. The entire assay can be performed in a microtiter plate and is amenable to automation. In addition, this peptidolysis assay is readily adaptable to other proteolytic enzymes and their substrates.

Amino Acid Sequence↗
PubMed1997

The 80's loop (residues 78 to 85) is important for the differential activity of retroviral proteases.

The abundance of structural data available for retroviral proteases affords a unique opportunity to investigate structure activity relationships. Our approach attempts to genetically engineer an HIV (human immunodeficiency virus)-1 protease that is functionally equivalent to the HIV-2 and the SIV (simian immunodeficiency virus) enzymes and conversely to engineer an HIV-2 protease that is functionally equivalent to the HIV-1 enzyme. For this purpose, the HIV-2 and SIV proteases were cloned and characterized in an Escherichia coli (E. coli) assay system along with 33 engineered HIV-1 and HIV-2 enzymes. The results of these experiments show that a relatively large S1 or S1' subsite volume, which is likely determined by the conformation of the 80's loop (residues 78 to 85), is necessary to fully accommodate the HIV-1 protease specificity site AETF*YCDG (the asterisk indicates the location scissile bond) during productive binding.

Amino Acid Sequence↗
PubMed1996

A heterologous substrate assay for the HIV-1 protease engineered in Escherichia coli.

A heterologous substrate assay for the human immunodeficiency virus type 1 (HIV-1) protease has been engineered in Escherichia coli. This assay detects the activity of the HIV-1 protease within intact bacterial cells and does not require biochemical purification of either the enzyme or the substrate. For this assay, nine HIV-1 protease specificity sites were genetically engineered into a heterologous protein (galactokinase) and the relative processing of these substrates by the wild-type and a substituted HIV-1 protease was determined. The results from these experiments revealed that the activity of the HIV-1 protease in the engineered heterologous substrate assay is consistent with previously reported in vitro assays and in vivo observations as well as a proposed catalytic specificity model.

Escherichia coli↗
PubMed1990

Anti-5 alpha-reductase autoantibodies in the serum of patients with prostatic cancer.

Human sera were tested for their ability to inhibit 5 alpha-reductase binding of a potent inhibitor of the enzyme. Thirty one of 227 serum samples from patients diagnosed or suspected of prostatic cancer had a significant inhibitory activity, whereas 128 serum samples from other patients were inactive. The majority of the inhibitory activity was in the IgG fraction purified by chromatography on a protein A-Sepharose affinity column and an anti-human IgG-agarose column. IgG fractions from non-inhibitory sera were inactive. Inhibitory IgG also inhibited the enzymatic activity of microsomal 5 alpha-reductase from liver, ventral prostate and preputial gland of rat, and liver, prostate, and facial skin of human. The inhibitory IgG had no effect on NADH-menadione reductase or 17 beta-hydroxysteroid dehydrogenase. These results suggest that 5 alpha-reductase autoantibodies are present in the blood of some prostatic cancer patients.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1989

Psychosocial issues of nutritional support. A multidisciplinary interpretation.

In many cases, initiation of specialized nutritional support is a final attempt at medically managing illness for which other treatments have failed. Patients may have suffered for months or even years with their underlying diseases and are usually aware that poor response to nutritional support and concurrent therapies may lead to surgical intervention or more complex treatment. In some cases, there may be few alternatives left to pursue. For such patients, this paints a very stressful picture. If we as caregivers are empathetic to each patient's situation, we are better able to offer the support that these patients need. Health care professionals must keep patients informed of treatment plans and encourage participation in the planning process--during hospitalization, through the discharge phase, and after hospitalization. We need to pay close attention to those needs, whether nutritional support is short-term during hospitalization, prolonged, or permanent. The health care environment is demanding greater proficiency in cost containment and quality assurance in the delivery of care. Complex patient cases are becoming more difficult to manage as time constraints and resources become more restrictive. The ingenuity and imagination of health care providers trying to find ways to continue providing high-quality and safe care to patients are being tested daily. These worthwhile goals can be met only through cooperation, communication, and support among all levels and disciplines involved with the delivery of care. Feelings of helplessness, dependence, and loss of control can be diminished if health care providers maintain optimistic, confident attitudes, offer positive reinforcement for patients successes, and try to restore hope during this stressful period in patients' lives.

Adult↗
PubMedDate not supplied

New opportunities for high-resolution solid-state NMR spectroscopy of oxide materials at 21.1- and 18.8-T fields.

We present here high-resolution solid state NMR spectra of several oxide and silicate materials that illustrate the improvements obtainable with very high external fields (18.8 and 21.1 T), with probes capable of tuning to a wide frequency range that allow observations of nuclides from high to low magnetogyric ratio. We discuss 27Al MAS spectra for the zeolite scolecite (CaAl2Si3O10 x 3H2O), 17O MAS data for analcime (NaAlSi2O6 x H2O), calcium monoaluminate (CaAI2O4), and titanite (CaTiSiO5), 39K spin-echo spectra for leucite (KAlSi2O6), microline (KAlSiO8), muscovite (KAl2(AlSi3O10)(OH2) and a potassium aluminosolicate glass, and preliminary 73Ge spin-echo MAS spectra for crystalline and glassy germanium dioxide (GeO2).

Magnetic Resonance Spectroscopy↗