Showing papers by "Sharad Kumar published in 2011"
TL;DR: It is shown that knockout of Nedd4-2 in mice leads to increased ENaC expression and activity in embryonic lung, which is the likely reason for premature fetal lung fluid clearance and a failure to inflate lungs and perinatal lethality.
Abstract: The epithelial sodium channel (ENaC) is essential for sodium homoeostasis in many epithelia. ENaC activity is required for lung fluid clearance in newborn animals and for maintenance of blood volume and blood pressure in adults. In vitro studies show that the ubiquitin ligase Nedd4-2 ubiquitinates ENaC to regulate its cell surface expression. Here we show that knockout of Nedd4-2 in mice leads to increased ENaC expression and activity in embryonic lung. This increased ENaC activity is the likely reason for premature fetal lung fluid clearance in Nedd4-2(-/-) animals, resulting in a failure to inflate lungs and perinatal lethality. A small percentage of Nedd4-2(-/-) animals survive up to 22 days, and these animals also show increased ENaC expression and develop lethal sterile inflammation of the lung. Thus, we provide critical in vivo evidence that Nedd4-2 is essential for correct regulation of ENaC expression, fetal and postnatal lung function and animal survival.
91 citations
TL;DR: It is shown that Dark forms a single ring when initiator procaspases are bound, and caspase recruitment domains (CARDs) form a crown on the central hub of the Dark apoptosome, which suggests that conformational changes will be required to form active Dark-Dronc complexes.
77 citations
TL;DR: It is reported that in Ndfip1(-/-) mice fed a low- iron diet, DMT1 expression and activity in duodenal enterocytes are significant higher than in the wild-type animals, which correlates with an increase in serum iron levels and transferrin saturation.
36 citations
TL;DR: dNdfip expression dramatically enhances dNedd4 and Su(dx)-mediated wing phenotypes and further disrupts Notch signaling, and a model whereby dNDFip promotes localization of Notch to the limiting membrane of late endosomes allowing for activation, similar to the model previously shown with ectopic Deltex expression is supported.
Abstract: In the Drosophila wing, the Nedd4 ubiquitin ligases (E3s), dNedd4 and Su(dx), are important negative regulators of Notch signaling; they ubiquitinate Notch, promoting its endocytosis and turnover. Here, we show that Drosophila Nedd4 family interacting protein (dNdfip) interacts with the Drosophila Nedd4-like E3s. dNdfip expression dramatically enhances dNedd4 and Su(dx)-mediated wing phenotypes and further disrupts Notch signaling. dNdfip colocalizes with Notch in wing imaginal discs and with the late endosomal marker Rab7 in cultured cells. In addition, dNdfip expression in the wing leads to ectopic Notch signaling. Supporting this, expression of dNdfip suppressed Notch+/− wing phenotype and knockdown of dNdfip enhanced the Notch+/− wing phenotype. The increase in Notch activity by dNdfip is ligand independent as dNdfip expression also suppressed deltex RNAi and Serrate+/− wing phenotypes. The opposing effects of dNdfip expression on Notch signaling and its late endosomal localization support a model whereby dNdfip promotes localization of Notch to the limiting membrane of late endosomes allowing for activation, similar to the model previously shown with ectopic Deltex expression. When dNedd4 or Su(dx) are also present, dNdfip promotes their activity in Notch ubiquitination and internalization to the lysosomal lumen for degradation.
25 citations
TL;DR: It is reported that GRK2 up-regulates the basal activity of the channel as a consequence of its RH domain binding the α-subunits of Gq/11 and that expression of constitutively active Gαq/ 11 mutants significantly inhibits activity of ENaC.
14 citations
4 citations