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Articles by S Brown
Total Records ( 16 ) for S Brown
  X Fan , Y Ding , S Brown , L Zhou , M Shaw , M. C Vella , H Cheng , E. C McNay , R. S Sherwin and R. J. McCrimmon
  In nondiabetic rodents, AMP-activated protein kinase (AMPK) plays a role in the glucose-sensing mechanism used by the ventromedial hypothalamus (VMH), a key brain region involved in the detection of hypoglycemia. However, AMPK is regulated by both hyper- and hypoglycemia, so whether AMPK plays a similar role in type 1 diabetes (T1DM) is unknown. To address this issue, we used four groups of chronically catheterized male diabetic BB rats, a rodent model of autoimmune T1DM with established insulin—requiring diabetes (40 ± 4 pmol/l basal c-peptide). Two groups were subjected to 3 days of recurrent hypoglycemia (RH), while the other two groups were kept hyperglycemic [chronic hyperglycemia (CH)]. All groups subsequently underwent hyperinsulinemic hypoglycemic clamp studies on day 4 in conjunction with VMH microinjection with either saline (control) or AICAR (5-aminoimidazole-4-carboxamide) to activate AMPK. Compared with controls, local VMH application of AICAR during hypoglycemia amplified both glucagon [means ± SE, area under the curve over time (AUC/t) 144 ± 43 vs. 50 ± 11 ng·l–1·min–1; P < 0.05] and epinephrine [4.27 ± 0.96 vs. 1.06 ± 0.26 nmol·l–1·min–1; P < 0.05] responses in RH-BB rats, and amplified the glucagon [151 ± 22 vs. 85 ± 22 ng·l–1·min–1; P < 0.05] response in CH-BB rats. We conclude that VMH AMPK also plays a role in glucose-sensing during hypoglycemia in a rodent model of T1DM. Moreover, our data suggest that it may be possible to partially restore the hypoglycemia-specific glucagon secretory defect characteristic of T1DM through manipulation of VMH AMPK.
  K. M Stepien , S Brown , A Taylor and L. Morgan
 

Silver toxicity is a rare condition. The most notable feature is a grey-blue discoloration of the skin, argyria, although harmful effects on the liver and kidney may be seen in severe cases. Neurological symptoms are an unusual consequence of silver toxicity. So far no effective treatment has been described for this metal overdose. We report the case of a 75-year-old man who had a history of self-medication with colloidal silver and presented with myoclonic seizures.

  M Garcia Fernandez , H Kissel , S Brown , T Gorenc , A. J Schile , S Rafii , S Larisch and H. Steller
 

Inhibitor of Apoptosis Proteins (IAPs) are frequently overexpressed in tumors and have become promising targets for developing anti-cancer drugs. IAPs can be inhibited by natural antagonists, but a physiological requirement of mammalian IAP antagonists remains to be established. Here we show that deletion of the mouse Sept4 gene, which encodes the IAP antagonist ARTS, promotes tumor development. Sept4-null mice have increased numbers of hematopoietic stem and progenitor cells, elevated XIAP protein, increased resistance to cell death, and accelerated tumor development in an Eµ-Myc background. These phenotypes are partially suppressed by inactivation of XIAP. Our results suggest that apoptosis plays an important role as a frontline defense against cancer by restricting the number of normal stem cells.

  U Chuluunbaatar , R Roller , M. E Feldman , S Brown , K. M Shokat and I. Mohr
 

All viruses require cellular ribosomes to translate their mRNAs. Viruses producing methyl-7 (m7) GTP-capped mRNAs, like Herpes Simplex Virus-1 (HSV-1), stimulate cap-dependent translation by activating mTORC1 to inhibit the translational repressor 4E-binding protein 1 (4E-BP1). Here, we establish that the HSV-1 kinase Us3 masquerades as Akt to activate mTORC1. Remarkably, Us3 displays no sequence homology with the cellular kinase Akt, yet directly phosphorylates tuberous sclerosis complex 2 (TSC2) on the same sites as Akt. TSC2 depletion rescued Us3-deficient virus replication, establishing that Us3 enhances replication by phosphorylating TSC2 to constitutively activate mTORC1, effectively bypassing S6K-mediated feedback inhibition. Moreover, Us3 stimulated Akt substrate phosphorylation in infected cells, including FOXO1 and GSK3. Thus, HSV-1 encodes an Akt surrogate with overlapping substrate specificity to activate mTORC1, stimulating translation and virus replication. This establishes Us3 as a unique viral kinase with promising drug development potential.

  G Markson , C Kiel , R Hyde , S Brown , P Charalabous , A Bremm , J Semple , J Woodsmith , S Duley , K Salehi Ashtiani , M Vidal , D Komander , L Serrano , P Lehner and C. M. Sanderson
 

In eukaryotic cells the stability and function of many proteins are regulated by the addition of ubiquitin or ubiquitin-like peptides. This process is dependent upon the sequential action of an E1-activating enzyme, an E2-conjugating enzyme, and an E3 ligase. Different combinations of these proteins confer substrate specificity and the form of protein modification. However, combinatorial preferences within ubiquitination networks remain unclear. In this study, yeast two-hybrid (Y2H) screens were combined with true homology modeling methods to generate a high-density map of human E2/E3-RING interactions. These data include 535 experimentally defined novel E2/E3-RING interactions and >1300 E2/E3-RING pairs with more favorable predicted free-energy values than the canonical UBE2L3–CBL complex. The significance of Y2H predictions was assessed by both mutagenesis and functional assays. Significantly, 74/80 (>92%) of Y2H predicted complexes were disrupted by point mutations that inhibit verified E2/E3-RING interactions, and a ~93% correlation was observed between Y2H data and the functional activity of E2/E3-RING complexes in vitro. Analysis of the high-density human E2/E3-RING network reveals complex combinatorial interactions and a strong potential for functional redundancy, especially within E2 families that have undergone evolutionary expansion. Finally, a one-step extended human E2/E3-RING network, containing 2644 proteins and 5087 edges, was assembled to provide a resource for future functional investigations.

  C. H Halbert , S Kumanyika , M Bowman , S. L Bellamy , V Briggs , S Brown , B Bryant , E Delmoor , J. C Johnson , J Purnell , R Rogers and B. Weathers
 

When using community-based participatory methods to develop health promotion programs for specific communities, it is important to determine if participation differs based on sociodemographics and the extent to which program participants are demographically representative of the target community, especially when non-random recruitment methods are used. We evaluated rates of participating in a health promotion program among African American residents in an urban community and determined if program participants were representative of community residents in terms of sociodemographic factors. While participation in the program was modest, participation did not differ based on psychological factors or body mass index. However, individuals who were unemployed were significantly more likely to participate in the program compared with those who were employed. Our sample included a greater proportion of individuals who only had a high school education compared with community residents but was similar to community residents in terms of gender, marital status and employment.

 
 
 
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