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Biomedical subjects

E Sternberg

Publications and source records attributed to E Sternberg.

14 recordsLinked to original sources
PubMed1990

A specific inhibitor of the ubiquitin activating enzyme: synthesis and characterization of adenosyl-phospho-ubiquitinol, a nonhydrolyzable ubiquitin adenylate analogue.

A nonhydrolyzable analogue of ubiquitin adenylate has been synthesized for use as a specific inhibitor of the ubiquitination of proteins. Ubiquitin adenylate is a tightly bound intermediate formed by the ubiquitin activating enzyme. The inhibitor adenosyl-phospho-ubiquitinol (APU) is the phosphodiester of adenosine and the C-terminal alcohol derived from ubiquitin. APU is isosteric with the normal reaction intermediate, the mixed anhydride of ubiquitin and AMP, but results from the replacement of the carbonyl oxygen of Gly76 with a methylene group. This stable analogue would be expected to bind to both ubiquitin and adenosine subsites and result in a tightly bound competitive inhibitor of ubiquitin activation. APU inhibits the ATP-PPi exchange reaction catalyzed by the purified ubiquitin activating enzyme in a manner competitive with ATP (Ki = 50 nM) and noncompetitive with ubiquitin (Ki = 35 nM). AMP has no effect on the inhibition, confirming that the inhibitor binds to the free form of the enzyme and not the thiol ester form. This inhibition constant is 10-fold lower than the dissociation constants for each substrate and 30-1000-fold lower than the respective Km values for ubiquitin and ATP. APU also effectively inhibits conjugation of ubiquitin to endogenous proteins catalyzed by reticulocyte fraction II with an apparent Ki of 0.75 microM. This weaker inhibition is consistent with the fact that activation of ubiquitin is not rate limiting in the conjugation reactions catalyzed by fraction II. APU is similarly effective as an inhibitor of the ubiquitin-dependent proteolysis of beta-lactoglobulin.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Monophosphate↗
PubMed1989

Ubiquitin function studied by disulfide engineering.

Disulfide engineering was used to probe the role of conformational mobility in ubiquitin-mediated proteolysis. Six genes that encode cysteine-containing mutants of ubiquitin were constructed, expressed in Escherichia coli and the proteins purified. Single cysteine-containing mutants and a 4/14 disulfide were active in degradation of a substrate protein in vitro, while the 4/66 disulfide, which cross-links the NH2- and COOH-terminal strands of the protein, was only 20-30% active. The solution structure of the 4/66 mutant was solved: the disulfide is left-handed with no perturbations in the backbone from that of wild type ubiquitin. The results suggest that conformational mobility is required for the activity of ubiquitin in signaling proteolysis.

Computer Simulation↗
PubMed1988

Instability of leukocyte aggregation: lack of evidence for leukoembolization during various states of inflammation.

This study centers on the question of whether the phenomenon of leukocyte aggregation, which is typical to inflammatory conditions, is pathogenic per se. We examined patients and laboratory animals in whom the presence of aggregated leukocytes in the peripheral blood was documented by direct visualization and where, despite the presence of aggregated leukocytes, neither the patients nor the laboratory animals showed clinical or pathological evidence for leukoembolization. Our in vitro findings about the reversibility of the phenomenon of leukocyte aggregation help to explain the above-mentioned observations as well as the well-known daily clinical experience that, despite complement activation and other aggregatory stimuli, there is no clinical or pathological evidence for leukoembolization.

Aged↗
PubMed1987

Induction of metallothionein is correlated with resistance to auranofin, a gold compound, in Chinese hamster ovary cells.

Metallothioneins (MTs) are low molecular weight, thiol-rich, metal-binding proteins. Auranofin (AF) is a gold compound active in the treatment of rheumatoid arthritis. The effects of AF on regulation of MT gene expression in Chinese hamster ovary cells were studied. AF-resistant cells accumulated substantial amounts of MT mRNA and protein, whereas no induction was observed in AF-sensitive cells. Cells capable of inducing MT in the presence of AF were much less sensitive to AF-mediated cytotoxicity. Induction of MT by low concentrations of Cd protected cells from subsequently administered doses of AF. The level of protection correlated with the level of induced MT. These findings indicate that MT plays a central role in the mechanisms underlying cellular resistance to gold compounds.

Animals↗
PubMed1986

Regulation of myogenic differentiation by type beta transforming growth factor.

Type beta transforming growth factor (TGF beta) has been shown to be both a positive and negative regulator of cellular proliferation and differentiation. The effects of TGF beta also are cell-type specific and appear to be modulated by other growth factors. In the present study, we examined the potential of TGF beta for control of myogenic differentiation. In mouse C-2 myoblasts, TGF beta inhibited fusion and prevented expression of the muscle-specific gene products, creatine kinase and acetylcholine receptor. Differentiation of the nonfusing muscle cell line, BC2Hl, was also inhibited by TGF beta in a dose-dependent manner (ID50 approximately 0.5 ng/ml). TGF beta was not mitogenic for either muscle cell line, indicating that its inhibitory effects do not require cell proliferation. Inhibition of differentiation required the continual presence of TGF beta in the culture media. Removal of TGF beta led to rapid appearance of muscle proteins, which indicates that intracellular signals generated by TGF beta are highly transient and require continuous occupancy of the TGF beta receptor. Northern blot hybridization analysis using a muscle creatine kinase cDNA probe indicated that TGF beta inhibited differentiation at the level of muscle-specific mRNA accumulation. These results provide the first demonstration that TGF beta is a potent regulator of myogenic differentiation and suggest that TGF beta may play an important role in the control of tissue-specific gene expression during development.

Animals↗
PubMed1978

[Typical forms of schizophrenia in old age].

Aside from typical forms of late schizophrenia which generally conform to the definition given by M. Bleuler, there also are psychoses appearing in old age which differ significantly from the atypical symptoms and consequently present certain diagnostic difficulties. This report contains descriptions of late manifestations in schizophrenic psychoses, which develop with a continuous or assault-like course with a prevalence of parnoial disorders. Paranoid delusions, in such cases, are characterized by aging traits (concrete and short-term delusions, exaggeration of the degree of superficial persecution and prejudice, and a limited number of people involved in the delusions). The development of such forms of late schizophrenia takes a slowly progressing course. The results of these studies, especially the psychopathological symptomatology, the genetic-constitutional background and the development and outcome of these psychoses are analyzed in detail. The data permit to consider such forms of psychose as atypical variants of late schizophrenia.

Adult↗
PubMed1977

[Acute psychoses of advanced age].

The group of acute psychoses in later life comprises: 1. acute psychotic pictures at the commencement or during the course of organic breakdown; 2. strictly speaking exogenous (symptomatic) psychoses 3. acute psychotic conditions during the processes in particular of endogenous psychoses; and 4. psychoreactive and situationally conditioned psychoses. In all these nosologically heterogeneous forms certain characteristics regarding their appearance and course can be perceived which are related to age a rudimentary type of syndromic pictures, their particular "senile" colouration, a preponderance of short and recurrent psychotic periods, a not infrequent change to dementia, and the occurrence of illnesses typical of old people (amnestic states of disorientation, complete optical illusions, etc.). The outlook for acute psychoses in later life is gloomy (almost 50% fatality); the recognition of basic illnesses causes particular difficulties. Some special clinical forms are being more intensively analysed.

Acute Disease↗