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Medicine Lodge, United States

Barash I.,50 First Avenue | Barash I.,New York Harbor Veterans Affairs Medical Center | Ponda M.P.,50 First Avenue | Ponda M.P.,Rockefeller University | And 4 more authors.
Clinical Journal of the American Society of Nephrology | Year: 2010

Background and objectives: Autosomal dominant polycystic kidney disease (ADPKD) leads to kidney failure in half of those affected. Increased levels of adenosine 3′:5′-cyclic monophosphate (cAMP) play a critical role in disease progression in animal models. Water loading, by suppressing arginine vasopressin (AVP)-stimulated cAMP production, is a proposed therapy for ADPKD. Design, setting, participants, & measurements: The effects of acute and sustained water loading on levels of urine osmolality (Uosm) and cAMP in 13 subjects with ADPKD and 10 healthy controls were studied. Uosm and cAMP concentrations were measured before and after water loading. Results: Urine [cAMP] indexed to Uosm significantly decreased with acute water loading in both groups (58% in controls and 35% in ADPKD). Chronic water loading resulted in a nonsignificant 13% decrease in 24-hour urine cAMP excretion in ADPKD participants, despite an increase in 24-hour urine volume by 64% to 3.14 ± 0.32 L and decrease in mean Uosm by 46%, to below that of plasma (270 ± 21 mOsm/L). Conclusions: Increased water intake of 3 L per day decreased Uosm in most ADPKD subjects. While urine [cAMP] accurately reflects changes in Uosm during acute water loading in ADPKD subjects, chronic water loading did not lower 24-hour urine cAMP excretion, although subjects with higher baseline [cAMP] (>2 nmol/mg Cr) responded best. Decreases in urine [cAMP] and osmolality are consistent with decreased AVP activity. These results support the need for a larger study to evaluate the effect of chronic water loading on ADPKD progression. Copyright © 2010 by the American Society of Nephrology. Source

Cai X.,Skirball Institute for Biomolecular Medicine | Srivastava S.,Skirball Institute for Biomolecular Medicine | Surindran S.,Skirball Institute for Biomolecular Medicine | Li Z.,Skirball Institute for Biomolecular Medicine | And 2 more authors.
Molecular Biology of the Cell | Year: 2014

The kidney, together with bone and intestine, plays a crucial role in maintaining whole-body calcium (Ca2+) homoeostasis, which is primarily mediated by altering the reabsorption of Ca2+ filtered by the glomerulus. The transient receptor potential-vanilloid-5 (TRPV5) channel protein forms a six- transmembrane Ca2+-permeable channel that regulates urinary Ca2+ excretion by mediating active Ca2+ reabsorption in the distal convoluted tubule of the kidney. Here we show that the histidine kinase, nucleoside diphosphate kinase B (NDPK-B), activates TRPV5 channel activity and Ca2+ flux, and this activation requires histidine 711 in the carboxy-terminal tail of TRPV5. In addition, the histidine phosphatase, protein histidine phosphatase 1, inhibits NDPK-B-activated TRPV5 in inside/out patch experiments. This is physiologically relevant to Ca2+ reabsorption in vivo, as short hairpin RNA knockdown of NDPK-B leads to decreased TRPV5 channel activity, and urinary Ca2+ excretion is increased in NDPK-B-/- mice fed a high-Ca2+ diet. Thus these findings identify a novel mechanism by which TRPV5 and Ca2+ reabsorption is regulated by the kidney and support the idea that histidine phosphorylation plays other, yet-uncovered roles in mammalian biology. © 2014 Hutchins. Source

Kuhn M.A.,New York University | Nayak S.,New York University | Camarena V.,Skirball Institute for Biomolecular Medicine | Gardner J.,New York University | And 4 more authors.
Otology and Neurotology | Year: 2012

Hypothesis: Reactivation of herpes simplex virus type 1 (HSV-1) in geniculate ganglion neurons (GGNs) is an etiologic mechanism of Bell's palsy (BP) and delayed facial palsy (DFP) after otologic surgery. Background: Several clinical studies, including temporal bone studies, antibody, titers, and intraoperative studies, suggest that reactivation of HSV-1 from latently infected GGNs may lead to both BP and DFP. However, it is difficult to study these processes in humans or live animals. Methods: Primary cultures of GGNs were latently infected with Patton strain HSV-1 expressing a green fluorescent protein-late lytic gene chimera. Four days later, these cultures were treated with trichostatin A (TSA), a known chemical reactivator of HSV-1 in other neurons. Cultures were monitored daily by fluorescent microscopy. Titers of media from lytic, latent, and latent/TSA treated GGN cultures were obtained using plaque assays on Vero cells. RNA was harvested from latently infected GGN cultures and examined for the presence of viral transcripts using reverse transcription-polymerase chain reaction. Results: Latently infected GGN cultures displayed latency-associated transcripts only, whereas lytically infected and reactivated latent cultures produced other viral transcripts, as well. The GGN cultures displayed a reactivation rate of 65% after treatment with TSA. Media from latently infected cultures contained no detectable infectious HSV-1, whereas infectious virus was observed in both lytically and latently infected/TSA-treated culture media. Conclusion: We have shown that cultured GGNs can be latently infected with HSV-1, and HSV-1 in these latently infected neurons can be reactivated using TSA, yielding infectious virus. These results have implications for the cause of both BP and DFP. © 2011, Otology & Neurotology, Inc. Source

Steinhauer J.,York College | Liu H.H.,Skirball Institute for Biomolecular Medicine | Miller E.,York College | Treisman J.E.,Skirball Institute for Biomolecular Medicine
Journal of Cell Science | Year: 2013

Epidermal growth factor receptor (EGFR) ligands undergo a complex series of processing events during their maturation to active signaling proteins. Like its mammalian homologs, the predominant Drosophila EGFR ligand Spitz is produced as a transmembrane pro-protein. In the secretory pathway, Spitz is cleaved within its transmembrane domain to release the extracellular signaling domain. This domain is modified with an N-terminal palmitate group that tethers it to the plasma membrane. We found that the pro-protein can reach the cell surface in the absence of proteolysis, but that it fails to activate the EGFR. To address why the transmembrane pro-protein is inactive, whereas membrane association through the palmitate group promotes activity, we generated a panel of chimeric constructs containing the Spitz extracellular region fused to exogenous transmembrane proteins. Although the orientation of the EGF domain and its distance from the plasma membrane varies in these chimeras, they are all active in vivo. Thus, tethering Spitz to the membrane via a transmembrane domain at either terminus does not prevent activity. Conversely, removing the N-terminal palmitate group from the C-terminally tethered pro-protein does not render it active. Furthermore, we show that the Spitz transmembrane pro-protein can activate the EGFR in a tissue culture assay, indicating that its failure to signal in vivo is not due to structural features. In polarized imaginal disc cells, unprocessed Spitz pro-protein localizes to apical puncta, whereas the active chimeric Spitz constructs are basolaterally localized. Taken together, our data support the model that localized trafficking of the pro-protein restricts its ability to activate the receptor in polarized tissues. © 2013. Published by The Company of Biologists Ltd. Source

Qin Z.,Skirball Institute for Biomolecular Medicine | Hubbard E.J.A.,Skirball Institute for Biomolecular Medicine
Nature Communications | Year: 2015

Stem cells maintain tissues and organs over the lifespan of individuals. How aging influences this process is unclear. Here we investigate the effects of aging on C. elegans germline stem/progenitor cells and show that the progenitor pool is depleted over time in a manner dependent on inhibition of DAF-16/FOXO by insulin/IGF-1 signalling (IIS). Our data indicate that DAF-16/FOXO activity in certain somatic gonad cells is required for germline progenitor maintenance, and that this role is separable from the effect of DAF-16/FOXO on organismal aging. In addition, blocking germ cell flux, similar to reducing IIS, maintains germline progenitors. This effect is partially dependent on gonadal DAF-16/FOXO activity. Our results imply that (1) longevity pathways can regulate aging stem cells through anatomically separable mechanisms, (2) stem cell maintenance is not necessarily prioritized and (3) stem cell regulation can occur at the level of an entire organ system such as the reproductive system. © 2015 Macmillan Publishers Limited. All rights reserved. Source

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