Journals
2009 EN
Jeffrey M. Yau · Anitha Pasupathy · Paul J. Fitzgerald
+2 more
We recognize, understand, and interact with objects through both vision and touch. Conceivably, these two sensory systems encode object shape in similar ways, which could facilitate cross-modal communication. To test this idea, we studied single neurons in macaque monkey intermediate visual (area V4) and somatosensory (area SII) cortex, using matched shape stimuli. We found similar patterns of shape sensitivity characterized by tuning for curvature direction. These parallel tuning patterns imply analogous shape coding mechanisms in intermediate visual and somatosensory cortex.
National Academy of Sciences
Journals
2009 EN
Matthew J. Potthoff · Takeshi Inagaki · Santhosh Satapati
+8 more
The liver plays a crucial role in mobilizing energy during nutritional deprivation. During the early stages of fasting, hepatic glycogenolysis is a primary energy source. As fasting progresses and glycogen stores are depleted, hepatic gluconeogenesis and ketogenesis become major energy sources. Here, we show that fibroblast growth factor 21 (FGF21), a hormone that is induced in liver by fasting, induces hepatic expression of peroxisome proliferator-activated receptor gamma coactivator protein-1alpha (PGC-1alpha), a key transcriptional regulator of energy homeostasis, and causes corresponding increases in fatty acid oxidation, tricarboxylic acid cycle flux, and gluconeogenesis without increasing glycogenolysis. Mice lacking FGF21 fail to fully induce PGC-1alpha expression in response to a prolonged fast and have impaired gluconeogenesis and ketogenesis. These results reveal an unexpected relationship between FGF21 and PGC-1alpha and demonstrate an important role for FGF21 in coordinately regulating carbohydrate and fatty acid metabolism during the progression from fasting to starvation.
National Academy of Sciences
Journals
2009 EN
Dingding Shi · Marius S. Pop · R. Kulikov
+3 more
p300 and CREB-binding protein (CBP) act as multifunctional regulators of p53 via acetylase and polyubiquitin ligase (E4) activities. Prior work in vitro has shown that the N-terminal 595 aa of p300 encode both generic ubiquitin ligase (E3) and p53-directed E4 functions. Analysis of p300 or CBP-deficient cells revealed that both coactivators were required for endogenous p53 polyubiquitination and the normally rapid turnover of p53 in unstressed cells. Unexpectedly, p300/CBP ubiquitin ligase activities were absent in nuclear extracts and exclusively cytoplasmic. Consistent with the cytoplasmic localization of its E3/E4 activity, CBP deficiency specifically stabilized cytoplasmic, but not nuclear p53. The N-terminal 616 aa of CBP, which includes the conserved Zn(2+)-binding C/H1-TAZ1 domain, was the minimal domain sufficient to destabilize p53 in vivo, and it included within an intrinsic E3 autoubiquitination activity and, in a two-step E4 assay, exhibited robust E4 activity for p53. Cytoplasmic compartmentalization of p300/CBP's ubiquitination function reconciles seemingly opposed functions and explains how a futile cycle is avoided-cytoplasmic p300/CBP E4 activities ubiquitinate and destabilize p53, while physically separate nuclear p300/CBP activities, such as p53 acetylation, activate p53.
National Academy of Sciences
Journals
2009 EN
P. Richard Grimm · Debra L. Irsik · Deann C. Settles
+2 more
Mice lacking the beta1-subunit (gene, Kcnmb1; protein, BK-beta1) of the large Ca-activated K channel (BK) are hypertensive. This phenotype is thought to result from diminished BK currents in vascular smooth muscle where BK-beta1 is an ancillary subunit. However, the beta1-subunit is also expressed in the renal connecting tubule (CNT), a segment of the aldosterone-sensitive distal nephron, where it associates with BK and facilitates K secretion. Because of the correlation between certain forms of hypertension and renal defects, particularly in the distal nephron, it was determined whether the hypertension of Kcnmb1(-/-) has a renal origin. We found that Kcnmb1(-/-) are hypertensive, volume expanded, and have reduced urinary K and Na clearances. These conditions are exacerbated when the animals are fed a high K diet (5% K; HK). Supplementing HK-fed Kcnmb1(-/-) with eplerenone (mineralocorticoid receptor antagonist) corrected the fluid imbalance and more than 70% of the hypertension. Finally, plasma [aldo] was elevated in Kcnmb1(-/-) under basal conditions (control diet, 0.6% K) and increased significantly more than wild type when fed the HK diet. We conclude that the majority of the hypertension of Kcnmb1(-/-) is due to aldosteronism, resulting from renal potassium retention and hyperkalemia.
National Academy of Sciences
Journals
2009 EN
Steven J. Clapcote · Steven Duffy · Gang Xie
+14 more
In a mouse mutagenesis screen, we isolated a mutant, Myshkin (Myk), with autosomal dominant complex partial and secondarily generalized seizures, a greatly reduced threshold for hippocampal seizures in vitro, posttetanic hyperexcitability of the CA3-CA1 hippocampal pathway, and neuronal degeneration in the hippocampus. Positional cloning and functional analysis revealed that Myk/+ mice carry a mutation (I810N) which renders the normally expressed Na(+),K(+)-ATPase alpha3 isoform inactive. Total Na(+),K(+)-ATPase activity was reduced by 42% in Myk/+ brain. The epilepsy in Myk/+ mice and in vitro hyperexcitability could be prevented by delivery of additional copies of wild-type Na(+),K(+)-ATPase alpha3 by transgenesis, which also rescued Na(+),K(+)-ATPase activity. Our findings reveal the functional significance of the Na(+),K(+)-ATPase alpha3 isoform in the control of epileptiform activity and seizure behavior.
National Academy of Sciences
Journals
2009 EN
Andreas AndroutsellisTheotokis · Maria Adele Rueger · Deric M. Park
+8 more
In Parkinson's disease, multiple cell types in many brain regions are afflicted. As a consequence, a therapeutic strategy that activates a general neuroprotective response may be valuable. We have previously shown that Notch ligands support neural precursor cells in vitro and in vivo. Here we show that neural precursors express the angiopoietin receptor Tie2 and that injections of angiopoietin2 activate precursors in the adult brain. Signaling downstream of Tie2 and the Notch receptor regulate blood vessel formation. In the adult brain, angiopoietin2 and the Notch ligand Dll4 activate neural precursors with opposing effects on the density of blood vessels. A model of Parkinson's disease was used to show that angiopoietin2 and Dll4 rescue injured dopamine neurons with motor behavioral improvement. A combination of growth factors with little impact on the vasculature retains the ability to stimulate neural precursors and protect dopamine neurons. The cellular and pharmacological basis of the neuroprotective effects achieved by these single treatments merits further analysis.
National Academy of Sciences
Journals
2009 EN
Yonghao Yu · Rana Anjum · Kazuishi Kubota
+3 more
Most kinases are capable of recognizing and phosphorylating peptides containing short, linear sequence motifs. To measure the activation state of many kinases from the same cell lysate, we created a multiplexed, mass-spectrometry-based in vitro kinase assay. Ninety chemically synthesized peptides derived from well-characterized peptide substrates and in vivo phosphorylation sites with either known or previously unidentified upstream kinases were reacted individually in a plate format with crude cell lysates and ATP. Phosphorylation rates were directly measured based on the addition of 90 same-sequence, site-specific phosphopeptides enriched in stable isotopes to act as ideal quantitative internal standards for analysis by liquid chromatography coupled to tandem mass spectrometry. This approach concurrently measured up to 90 site-specific peptide phosphorylation rates, reporting a diagnostic fingerprint for activated kinase pathways. We applied this unique kinome-activity profiling strategy in a variety of cellular settings, including mitogen stimulation, cell cycle, pharmacological inhibition of pathways, and to a panel of breast cancer cell lines. Finally, we identified the source of activity for a peptide (derived from a PI3K regulatory subunit) from our library. This peptide substrate demonstrated mitotic and tyrosine-specific phosphorylation, which was confirmed to be a novel Src family kinase site in vivo.
National Academy of Sciences
Journals
2009 EN
Andrew R. Burke · Xuanfeng Ding · Ravi Singh
+15 more
Multiwalled carbon nanotubes (MWCNTs) exhibit physical properties that render them ideal candidates for application as noninvasive mediators of photothermal cancer ablation. Here, we demonstrate that use of MWCNTs to generate heat in response to near-infrared radiation (NIR) results in thermal destruction of kidney cancer in vitro and in vivo. We document the thermal effects of the therapy through magnetic resonance temperature-mapping and heat shock protein-reactive immunohistochemistry. Our results demonstrate that use of MWCNTs enables ablation of tumors with low laser powers (3 W/cm(2)) and very short treatment times (a single 30-sec treatment) with minimal local toxicity and no evident systemic toxicity. These treatment parameters resulted in complete ablation of tumors and a >3.5-month durable remission in 80% of mice treated with 100 microg of MWCNT. Use of MWCNTs with NIR may be effective in anticancer therapy.
National Academy of Sciences
Journals
2009 EN
Laura Herrero · Hagit Shapiro · Ali Nayer
+2 more
Lipodystrophy and obesity are opposites in terms of a deficiency versus excess of adipose tissue mass, yet these conditions are accompanied by similar metabolic consequences, including insulin resistance, dyslipidemia, hepatic steatosis, and increased risk for diabetes and atherosclerosis. Hepatic and myocellular steatosis likely contribute to metabolic dysregulation in both states. Inflammation and macrophage infiltration into adipose tissue also appear to participate in the pathogenesis of obesity-induced insulin resistance, but their contributions to lipodystrophy-induced insulin resistance have not been evaluated. We used aP2-nSREBP-1c transgenic (Tg) mice, an established model of lipodystrophy, to ask this question. Circulating cytokine elevations suggested systemic inflammation but even more dramatic was the number of infiltrating macrophages in all white and brown adipose tissue depots of the Tg mice; in contrast, there was no evidence of inflammatory infiltrates or responses in any other tissue including liver. Despite there being overt evidence of adipose tissue inflammation, antiinflammatory strategies including salicylate treatment and genetic suppression of myeloid NF-kappaB signaling that correct insulin resistance in obesity were ineffective in the lipodystrophic mice. We further showed that adipose tissue macrophages (ATMs) in lipodystrophy and obesity are very different in terms of activation state, gene expression patterns, and response to lipopolysaccharide. Although ATMs are even more abundant in lipodystrophy than in obesity, they have distinct phenotypes and likely roles in tissue remodeling, but do not appear to be involved in the pathogenesis of insulin resistance.
National Academy of Sciences
Journals
2009 EN
Marty L. Montpetit · Patrick J. Stocker · Tara A. Schwetz
+11 more
Millions afflicted with Chagas disease and other disorders of aberrant glycosylation suffer symptoms consistent with altered electrical signaling such as arrhythmias, decreased neuronal conduction velocity, and hyporeflexia. Cardiac, neuronal, and muscle electrical signaling is controlled and modulated by changes in voltage-gated ion channel activity that occur through physiological and pathological processes such as development, epilepsy, and cardiomyopathy. Glycans attached to ion channels alter channel activity through isoform-specific mechanisms. Here we show that regulated and aberrant glycosylation modulate cardiac ion channel activity and electrical signaling through a cell-specific mechanism. Data show that nearly half of 239 glycosylation-associated genes (glycogenes) were significantly differentially expressed among neonatal and adult atrial and ventricular myocytes. The N-glycan structures produced among cardiomyocyte types were markedly variable. Thus, the cardiac glycome, defined as the complete set of glycan structures produced in the heart, is remodeled. One glycogene, ST8sia2, a polysialyltransferase, is expressed only in the neonatal atrium. Cardiomyocyte electrical signaling was compared in control and ST8sia2((-/-)) neonatal atrial and ventricular myocytes. Action potential waveforms and gating of less sialylated voltage-gated Na+ channels were altered consistently in ST8sia2((-/-)) atrial myocytes. ST8sia2 expression had no effect on ventricular myocyte excitability. Thus, the regulated (between atrium and ventricle) and aberrant (knockout in the neonatal atrium) expression of a single glycogene was sufficient to modulate cardiomyocyte excitability. A mechanism is described by which cardiac function is controlled and modulated through physiological and pathological processes that involve regulated and aberrant glycosylation.
National Academy of Sciences