Proceedings of the National Academy of Sciences of the United States of America
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Proc. Natl. Acad. Sci. U.S.A. · Mar 1999
Tonicity-responsive enhancer binding protein, a rel-like protein that stimulates transcription in response to hypertonicity.
Hypertonicity (most often present as high salinity) is stressful to the cells of virtually all organisms. Cells survive in a hypertonic environment by increasing the transcription of genes whose products catalyze cellular accumulation of compatible osmolytes. In mammals, the kidney medulla is normally hypertonic because of the urinary concentrating mechanism. ⋯ Tonicity-responsive enhancers (TonE) play a key role in hypertonicity-induced transcriptional stimulation of SMIT, sodium/chloride/betaine cotransporter, and aldose reductase. We report the cDNA cloning of human TonE binding protein (TonEBP), a transcription factor that stimulates transcription through its binding to TonE sequences via a Rel-like DNA binding domain. Western blot and immunohistochemical analyses of cells cultured in hypertonic medium reveal that exposure to hypertonicity elicits slow activation of TonEBP, which is the result of an increase in TonEBP amount and translocation to the nucleus.
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Proc. Natl. Acad. Sci. U.S.A. · Mar 1999
A neomorphic syntaxin mutation blocks volatile-anesthetic action in Caenorhabditis elegans.
The molecular mechanisms underlying general anesthesia are unknown. For volatile general anesthetics (VAs), indirect evidence for both lipid and protein targets has been found. However, no in vivo data have implicated clearly any particular lipid or protein in the control of sensitivity to clinical concentrations of VAs. ⋯ A single gene mutation conferring high-level resistance to VAs is inconsistent with nonspecific membrane-perturbation theories of anesthesia. The genetic and pharmacological data suggest that the resistant syntaxin mutant directly blocks VA binding to or efficacy against presynaptic targets that mediate anesthetic behavioral effects. Syntaxin and syntaxin-binding proteins are candidate anesthetic targets.
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Proc. Natl. Acad. Sci. U.S.A. · Mar 1999
Growth factor-mediated Fyn signaling regulates alpha-amino-3- hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor expression in rodent neocortical neurons.
Src-family protein tyrosine kinases (PTKs) transduce signals to regulate neuronal development and synaptic plasticity. However, the nature of their activators and molecular mechanisms underlying these neural processes are unknown. Here, we show that brain-derived neurotrophic factor (BDNF) and platelet-derived growth factor enhance expression of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptor 1 and 2/3 proteins in rodent neocortical neurons via the Src-family PTK(s). ⋯ Moreover, the neocortex of young Fyn mutants exhibited a significant in vivo reduction in these AMPA receptor proteins but not in their mRNA levels. In vitro kinase assay revealed that BDNF can indeed activate the Fyn kinase: It enhanced tyrosine phosphorylation of Fyn as well as that of enolase supplemented exogenously. All of these results suggest that the Src-family kinase Fyn, activated by the growth factors, plays a crucial role in modulating AMPA receptor expression during brain development.
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Proc. Natl. Acad. Sci. U.S.A. · Jan 1999
Systemic biosynthesis of prostacyclin by cyclooxygenase (COX)-2: the human pharmacology of a selective inhibitor of COX-2.
Prostaglandins (PG) are synthesized by two isoforms of the enzyme PG G/H synthase [cyclooxygenase (COX)]. To examine selectivity of tolerated doses of an inhibitor of the inducible COX-2 in humans, we examined the effects of celecoxib on indices of COX-1-dependent platelet thromboxane (Tx) A2 and on systemic biosynthesis of prostacyclin in vivo. Volunteers received doses of 100, 400, or 800 mg of celecoxib or 800 mg of a nonselective inhibitor, ibuprofen. ⋯ There was no significant difference between the doses of celecoxib on COX-2 inhibition. Celecoxib and ibuprofen suppressed urinary excretion of the prostacyclin metabolite 2,3 dinor 6-keto PGF1alpha. These data suggest that (i) platelet COX-1-dependent aggregation is not inhibited by up to 800 mg of celecoxib; (ii) comparable COX-2 inhibition is attained by celecoxib (100-800 mg) and ibuprofen (800 mg) after acute dosing; and (iii) COX-2 is a major source of systemic prostacyclin biosynthesis in healthy humans.
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Proc. Natl. Acad. Sci. U.S.A. · May 1998
Enhancing leptin response by preventing SH2-containing phosphatase 2 interaction with Ob receptor.
Leptin is an adipocyte-derived cytokine that regulates food intake and body weight via interaction with its Ob receptor (ObR). Serum leptin levels are chronically elevated in obese humans, suggesting that obesity may be associated with leptin resistance and the inability to generate an adequate ObR response. ⋯ Surprisingly, mutation of Tyr986 to Phe, which abrogates SHP-2 phosphorylation and binding to the receptor, dramatically increases gene induction mediated by STAT3. Our findings indicate that SHP-2 is a negative regulator of STAT3-mediated gene induction after activation of ObR and raise the possibility that blocking the interaction of SHP-2 with ObR could overcome leptin resistance by boosting leptin's weight-reducing effects in obese individuals.