Biomedical subjects

M Gurney

Publications and source records attributed to M Gurney.

12 recordsLinked to original sources

PubMed2001

The Notch intracellular domain is ubiquitinated and negatively regulated by the mammalian Sel-10 homolog.

The Caenorhabditis elegans sel-10 protein is structurally similar to E3 ubiquitin ligases and is a negative regulator of Notch (lin-12) and presenilin signaling. In this report, we characterize the mammalian Sel-10 homolog (mSel-10) and analyze its effects on Notch signaling. We find that mSel-10 localizes to the cell nucleus, and that it physically interacts with the Notch 1 intracellular domain (IC) and reduces Notch 1 IC-mediated activation of the HES 1 promoter. Notch 1 IC is ubiquitinated by mSel-10, and ubiquitination requires the presence of the most carboxyl-terminal region of the Notch IC, including the PEST domain. In the presence of the proteasome inhibitor MG132, the amount of Notch 1 IC and its level of ubiquitination are increased. Interestingly, this accumulation of Notch 1 IC in the presence of MG132 is accompanied by decreased activation of the HES 1 promoter, suggesting that ubiquitinated Notch 1 IC is a less potent transactivator. Finally, we show that mSel-10 itself is ubiquitinated and degraded by the proteasome. In conclusion, these data reveal the importance of ubiquitination and proteasome-mediated degradation for the activity and turnover of Notch ICs, and demonstrate that mSel-10 plays a key role in this process.

Amino Acid Sequence↗

PubMed2001

SEL-10 is an inhibitor of notch signaling that targets notch for ubiquitin-mediated protein degradation.

Notch receptors and their ligands play important roles in both normal animal development and pathogenesis. We show here that the F-box/WD40 repeat protein SEL-10 negatively regulates Notch receptor activity by targeting the intracellular domain of Notch receptors for ubiquitin-mediated protein degradation. Blocking of endogenous SEL-10 activity was done by expression of a dominant-negative form containing only the WD40 repeats. In the case of Notch1, this block leads to an increase in Notch signaling stimulated by either an activated form of the Notch1 receptor or Jagged1-induced signaling through Notch1. Expression of dominant-negative SEL-10 leads to stabilization of the intracellular domain of Notch1. The Notch4 intracellular domain bound to SEL-10, but its activity was not increased as a result of dominant-negative SEL-10 expression. SEL-10 bound Notch4 via the WD40 repeats and bound preferentially to a phosphorylated form of Notch4 in cells. We mapped the region of Notch4 essential for SEL-10 binding to the C-terminal region downstream of the ankyrin repeats. When this C-terminal fragment of Notch4 was expressed in cells, it was highly labile but could be stabilized by the expression of dominant-negative SEL-10. Ubiquitination of Notch1 and Notch4 intracellular domains in vitro was dependent on SEL-10. Although SEL-10 interacts with the intracellular domains of both Notch1 and Notch4, these proteins respond differently to interference with SEL-10 function. Thus, SEL-10 functions to promote the ubiquitination of Notch proteins; however, the fates of these proteins may differ.

Animals↗

PubMed1998

Metabolic dysfunction in familial, but not sporadic, amyotrophic lateral sclerosis.

Autosomal dominant familial amyotrophic lateral sclerosis (FALS) is associated with mutations in the gene encoding Cu/Zn superoxide dismutase (SOD1). Previous studies have implicated the involvement of metabolic dysfunction in ALS pathogenesis. To further investigate the biochemical features of FALS and sporadic ALS (SALS), we examined SOD activity and mitochondrial oxidative phosphorylation enzyme activities in motor cortex (Brodmann area 4), parietal cortex (Brodmann area 40), and cerebellum from control subjects, FALS patients with and without known SOD mutations, SALS patients, and disease controls (Pick's disease, progressive supranuclear palsy, diffuse Lewy body disease). Cytosolic SOD activity, predominantly Cu/Zn SOD, was decreased approximately 50% in all regions in FALS patients with SOD mutations but was not significantly altered in other patient groups. Marked increases in complex I and II-III activities were seen in FALS patients with SOD mutations but not in SALS patients. We also measured electron transport chain enzyme activities in a transgenic mouse model of FALS. Complex I activity was significantly increased in the forebrain of 60-day-old G93A transgenic mice overexpressing human mutant SOD1, relative to levels in transgenic wild-type animals, supporting the hypothesis that the motor neuron disorder associated with SOD1 mutations involves a defect in mitochondrial energy metabolism.

Adult↗

PubMed1997

Progressive motor neuron impairment in an animal model of familial amyotrophic lateral sclerosis.

Mutations of Cu,Zn superoxide dismutase cause an autosomal dominant form of familial amyotrophic lateral sclerosis. An animal model of the disease has been produced by expressing mutant human SOD1 in transgenic mice (G93A). In order to quantify the dysfunction of the motor unit in transgenic mice, electromyographic recordings were performed during the course of the disease. The first alterations in neuromuscular function appeared between P63 and P90. The deficits became even more striking after P100; compound muscle action potentials in the hindlimb decreased by 80% of initial value. Spontaneous fibrillation potentials were measured in more than 50% of transgenic mice. The number of motor units in the gastrocnemius muscle was progressively reduced over time, down to 18% of the control value at P130. Moreover, distal motor latencies increased after P120. These data suggest that the initial dysfunctions of motor unit are related to a severe motor axonal degeneration, which is followed at later periods by myelin alteration.

Amyotrophic Lateral Sclerosis↗

PubMed1988

The global prevalence of obesity--an initial overview of available data.

Methods of measuring obesity are briefly reviewed. The more precise methods of measuring the body-fat mass are too complex and expensive for use in regular public health practice or individual screening. Anthropometry can, however, provide useful information. Two anthropometric indicators of obesity or overweight are recommended for classifying obesity. For adults, the body-mass index is reasonably easy to obtain and correlates well with mortality and morbidity risk. For children, "overweight" is indicated by a weight-for-height above the median NCHS value plus two standard deviations. Data compiled by the WHO Nutrition Unit, using these two indicators, are presented for a number of countries worldwide in Table 1 & Fig. 1.

Adult↗

PubMed1985

Comparison of single-dose tetracycline hydrochloride to conventional therapy of urinary tract infections.

Sixty-two women with signs and symptoms compatible with lower urinary tract infections were randomized to receive single-dose tetracycline (2 g), multi-dose tetracycline (500 mg four times per day for 10 days), or single-dose amoxicillin (3 g). Urine cultures were obtained upon entry into the study and on days 4, 14, and 28 after therapy. Single-dose tetracycline cured 12 of 16 (75%) of women with documented urinary tract infections, compared with 15 of 16 (94%) in the multi-dose tetracycline group and 7 of 13 (54%) receiving single-dose amoxicillin. Mild nausea in 3 of 20 patients (15%) was the only complication in the single-dose tetracycline group. Two grams of single-dose tetracycline is as effective as other reported regimens regardless of the susceptibility of the initial pathogen and has minimal toxicity.

Adolescent↗

PubMed1981