scholarly journals Spliced XBP1 Rescues Renal Interstitial Inflammation Due to Loss of Sec63 in Collecting Ducts

2019 ◽  
Vol 30 (3) ◽  
pp. 443-459 ◽  
Author(s):  
Yasunobu Ishikawa ◽  
Sorin Fedeles ◽  
Arnaud Marlier ◽  
Chao Zhang ◽  
Anna-Rachel Gallagher ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Genetic Model ◽  
Collecting Duct ◽  
Kidney Injury ◽  
Endoplasmic Reticulum Membrane ◽  
Double Knockout ◽  
Embryonic Mouse ◽  
Interstitial Inflammation ◽  
Collecting Ducts

BackgroundSEC63 encodes a resident protein in the endoplasmic reticulum membrane that, when mutated, causes human autosomal dominant polycystic liver disease. Selective inactivation of Sec63 in all distal nephron segments in embryonic mouse kidney results in polycystin-1–mediated polycystic kidney disease (PKD). It also activates the Ire1α-Xbp1 branch of the unfolded protein response, producing Xbp1s, the active transcription factor promoting expression of specific genes to alleviate endoplasmic reticulum stress. Simultaneous inactivation of Xbp1 and Sec63 worsens PKD in this model.MethodsWe explored the renal effects of postnatal inactivation of Sec63 alone or with concomitant inactivation of Xbp1 or Ire1α, specifically in the collecting ducts of neonatal mice.ResultsThe later onset of inactivation of Sec63 restricted to the collecting duct does not result in overt activation of the Ire1α-Xbp1 pathway or cause polycystin-1–dependent PKD. Inactivating Sec63 along with either Xbp1 or Ire1α in this model causes interstitial inflammation and associated fibrosis with decline in kidney function over several months. Re-expression of XBP1s in vivo completely rescues the chronic kidney injury observed after inactivation of Sec63 with either Xbp1 or Ire1α.ConclusionsIn the absence of Sec63, basal levels of Xbp1s activity in collecting ducts is both necessary and sufficient to maintain proteostasis (protein homeostasis) and protect against inflammation, myofibroblast activation, and kidney functional decline. The Sec63-Xbp1 double knockout mouse offers a novel genetic model of chronic tubulointerstitial kidney injury, using collecting duct proteostasis defects as a platform for discovery of signals that may underlie CKD of disparate etiologies.

scholarly journals Ceramide chain length–dependent protein sorting into selective endoplasmic reticulum exit sites

2020 ◽  
Vol 6 (50) ◽  
pp. eaba8237
Author(s):  
Sofia Rodriguez-Gallardo ◽  
Kazuo Kurokawa ◽  
Susana Sabido-Bozo ◽  
Alejandro Cortes-Gomez ◽  
Atsuko Ikeda ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Chain Length ◽  
Secretory Pathway ◽  
Protein Sorting ◽  
Endoplasmic Reticulum Membrane ◽  
Lipid Chain ◽  
Secretory Transport ◽  
Dependent Protein ◽  
Cellular Compartmentalization

Protein sorting in the secretory pathway is crucial to maintain cellular compartmentalization and homeostasis. In addition to coat-mediated sorting, the role of lipids in driving protein sorting during secretory transport is a longstanding fundamental question that still remains unanswered. Here, we conduct 3D simultaneous multicolor high-resolution live imaging to demonstrate in vivo that newly synthesized glycosylphosphatidylinositol-anchored proteins having a very long chain ceramide lipid moiety are clustered and sorted into specialized endoplasmic reticulum exit sites that are distinct from those used by transmembrane proteins. Furthermore, we show that the chain length of ceramide in the endoplasmic reticulum membrane is critical for this sorting selectivity. Our study provides the first direct in vivo evidence for lipid chain length–based protein cargo sorting into selective export sites of the secretory pathway.

scholarly journals Biosynthesis and processing of ribophorins in the endoplasmic reticulum.

1984 ◽  
Vol 99 (3) ◽  
pp. 1076-1082 ◽  
Author(s):  
M G Rosenfeld ◽  
E E Marcantonio ◽  
J Hakimi ◽  
V M Ort ◽  
P H Atkinson ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Posttranslational Modifications ◽  
Rat Hepatocytes ◽  
Direct Analysis ◽  
In Vitro Translation ◽  
Endoplasmic Reticulum Membrane ◽  
Pituitary Cells ◽  
Amino Terminal

Ribophorins are two transmembrane glycoproteins characteristic of the rough endoplasmic reticulum, which are thought to be involved in the binding of ribosomes. Their biosynthesis was studied in vivo using lines of cultured rat hepatocytes (clone 9) and pituitary cells (GH 3.1) and in cell-free synthesis experiments. In vitro translation of mRNA extracted from free and bound polysomes of clone 9 cells demonstrated that ribophorins are made exclusively on bound polysomes. The primary translation products of ribophorin messengers obtained from cultured hepatocytes or from regenerating livers co-migrated with the respective mature proteins, but had slightly higher apparent molecular weights (2,000) than the unglycosylated forms immunoprecipitated from cells treated with tunicamycin. This indicates that ribophorins, in contrast to all other endoplasmic reticulum membrane proteins previously studied, contain transient amino-terminal insertion signals which are removed co-translationally. Kinetic and pulse-chase experiments with [35S]methionine and [3H]mannose demonstrated that ribophorins are not subjected to electrophoretically detectable posttranslational modifications, such as proteolytic cleavage or trimming and terminal glycosylation of oligosaccharide side chain(s). Direct analysis of the oligosaccharides of ribophorin l showed that they do not contain the terminal sugars characteristic of complex oligosaccharides and that they range in composition from Man8GlcNAc to Man5GlcNAc. These findings, as well as the observation that the mature proteins are sensitive to endoglycosidase H and insensitive to endoglycosidase D, are consistent with the notion that the biosynthetic pathway of the ribophorins does not require a stage of passage through the Golgi apparatus.

Deoxycorticosterone-stimulated bicarbonate secretion in rabbit cortical collecting ducts: effects of luminal chloride removal and in vivo acid loading

1985 ◽  
Vol 249 (2) ◽  
pp. F205-F212 ◽  
Author(s):  
J. Garcia-Austt ◽  
D. W. Good ◽  
M. B. Burg ◽  
M. A. Knepper
Keyword(s):  
Collecting Duct ◽  
High Rate ◽  
Bicarbonate Secretion ◽  
Cortical Collecting Duct ◽  
Acid Base ◽  
Urinary Ph ◽  
Collecting Ducts ◽  
Acid Loading

To assess the role of cortical collecting duct bicarbonate secretion in the regulation of net acid excretion, we have sought to identify what factors influence the secretion rate. Net and unidirectional bicarbonate fluxes were measured in isolated perfused cortical collecting ducts from deoxycorticosterone-treated rabbits. The collecting ducts secreted bicarbonate at 11-24 pmol X mm-1 X min-1, confirming the high rate seen in earlier studies. Oral acid loading (50 mM NH4Cl drinking water) completely inhibited the net bicarbonate secretion. The bath-to-lumen flux was markedly reduced with acid loading, but the lumen-to-bath flux changed very little. In tubules from rabbits treated with deoxycorticosterone (but not NH4Cl), luminal chloride replacement with either sulfate or gluconate completely and reversibly inhibited the net bicarbonate secretion. The bath-to-lumen flux was greatly inhibited, but there was little change in the lumen-to-bath flux. We conclude: 1) High rates of bicarbonate secretion can be induced in rabbit cortical collecting ducts by chronic treatment of the animals with deoxycorticosterone. 2) When deoxycorticosterone-treated rabbits were made acidotic by oral administration of NH4Cl, the bicarbonate secretion was prevented, indicating that the systemic acid-base state of the animal may be an important factor regulating bicarbonate secretion. 3) Replacement of chloride in the lumen with sulfate inhibits bicarbonate secretion in the cortical collecting duct, an effect which may explain in part the decrease in urinary pH in response to sulfate infusions in mineralocorticoid-stimulated animals.

scholarly journals Gentamicin-Induced Acute Kidney Injury in an Animal Model Involves Programmed Necrosis of the Collecting Duct

2020 ◽  
Vol 31 (9) ◽  
pp. 2097-2115 ◽  
Author(s):  
Huihui Huang ◽  
William W. Jin ◽  
Ming Huang ◽  
Heyu Ji ◽  
Diane E. Capen ◽  
...  
Keyword(s):  
Cultured Cells ◽  
Collecting Duct ◽  
Kidney Injury ◽  
Aminoglycoside Antibiotic ◽  
Kinase Domain ◽  
Programmed Necrosis ◽  
Proximal Tubule Cells ◽  
Cell Death Pathways ◽  
Collecting Ducts ◽  
Tubule Cells

BackgroundGentamicin is a potent aminoglycoside antibiotic that targets gram-negative bacteria, but nephrotoxicity limits its clinical application. The cause of gentamicin-induced AKI has been attributed mainly to apoptosis of the proximal tubule cells. However, blocking apoptosis only partially attenuates gentamicin-induced AKI in animals.MethodsMice treated with gentamicin for 7 days developed AKI, and programmed cell death pathways were examined using pharmacologic inhibitors and in RIPK3-deficient mice. Effects in porcine and murine kidney cell lines were also examined.ResultsGentamicin caused a low level of apoptosis in the proximal tubules and significant ultrastructural alterations consistent with necroptosis, occurring predominantly in the collecting ducts (CDs), including cell and organelle swelling and rupture of the cell membrane. Upregulation of the key necroptotic signaling molecules, mixed lineage kinase domain-like pseudokinase (MLKL) and receptor-interacting serine/threonine-protein kinase 3 (RIPK3), was detected in gentamicin-treated mice and in cultured renal tubule cells. In addition, gentamicin induced apical accumulation of total and phosphorylated MLKL (pMLKL) in CDs in mouse kidney. Inhibiting a necroptotic protein, RIPK1, with necrostatin-1 (Nec-1), attenuated gentamicin-induced necrosis and upregulation of MLKL and RIPK3 in mice and cultured cells. Nec-1 also alleviated kidney inflammation and fibrosis, and significantly improved gentamicin-induced renal dysfunction in mice. Furthermore, deletion of RIPK3 in the Ripk3−/− mice significantly attenuated gentamicin-induced AKI.ConclusionsA previously unrecognized role of programmed necrosis in collecting ducts in gentamicin-induced kidney injury presents a potential new therapeutic strategy to alleviate gentamicin-induced AKI through inhibiting necroptosis.

A method for exposing the rat renal medulla in vivo: micropuncture of the collecting duct

1965 ◽  
Vol 209 (3) ◽  
pp. 663-668 ◽  
Author(s):  
Fuminori Sakai ◽  
Rex L. Jamison ◽  
Robert W. Berliner
Keyword(s):  
Collecting Duct ◽  
Left Kidney ◽  
Electrical Potential ◽  
Renal Medulla ◽  
Distal Portion ◽  
Urinary Flow ◽  
Osmotic Gradient ◽  
Collecting Ducts ◽  
Microelectrode Techniques

A new method involving partial nephrectomy is described by which the distal portion of the rat renal medulla is made accessible to an investigation by the micropuncture technique. Urinary flow was greater and osmolality less in the partially nephrectomized left kidney than the unoperated right kidney but the urine remained hypertonic. Micropuncture of the collecting duct revealed a rising osmotic gradient toward the papillary tip. Electrical potential differences across the collecting ducts were measured by microelectrode techniques. The lumen was electrically negative with respect to the interstitial fluid (mean - 11 mv). It is clear that medullary hypertonicity persists in the partially nephrectomized left kidney and the collecting ducts retain their ability to reabsorb water and maintain a transtubular potential difference. In these aspects of tubular activity, the exposed rat renal medulla appears to be similar to that of the hamster, but has the advantage of a greater exposure of its length to investigation by micropuncture.

Tubular prostaglandin E2 production and its role in urinary hypotonicity after release of ureteral occlusion in the rat

1987 ◽  
Vol 73 (4) ◽  
pp. 395-399 ◽  
Author(s):  
Shozo Torikai
Keyword(s):  
Prostaglandin E2 ◽  
Collecting Duct ◽  
Urine Osmolality ◽  
Urine Concentration ◽  
Pge2 Production ◽  
Endogenous Prostaglandin ◽  
Collecting Ducts ◽  
Ureteral Occlusion

1. In order to explore the involvement of endogenous prostaglandin E2 (PGE2) in the urine concentration defect after ureteral occlusion, PGE2 production by isolated collecting ducts in vitro and effects of indomethacin on urine osmolality in vivo were examined. 2. Twenty-four hours ureter obstruction caused increased PGE2 production by the medullary collecting ducts, which was maintained at a high level on the day after release of obstruction (0.8 ± 0.2 pg/mm normal, 8.1 ± 0.9 pg/mm 24 h obstruction, and 6.6 ± 1.0 pg/mm post-obstruction, mean ± sem). An enhanced PGE2 production was also observed for papillary collecting duct on the day after release of 24 h ureteral occlusion (3.9 ± 0.5 pg/mm normal and 7.7 ± 1.2 pg/mm post-obstruction). 3. Administration of indomethacin to the unilateral post-obstructive rats slightly raised the urine osmolality of the post-obstructed kidney (from 339 ± 17 to 390 ± 22 mosmol/kg H2O), while it had a greater effect on the contralateral intact kidney (from 1569 ± 138 to 2567 ± 198 mosmol/kg H2O). 4. Our data may indicate that the urine concentration defect after 24 h ureteral occlusion is ascribable mainly to a mechanism other than increased endogenous PGE2.

scholarly journals 629: Endoplasmic reticulum membrane complex is required for CFTR biogenesis and activation in vivo

2021 ◽  
Vol 20 ◽  
pp. S299
Author(s):  
Y. Huang ◽  
X. Tang ◽  
T. Weaver ◽  
J. Whitsett ◽  
A. Naren
Keyword(s):  
Endoplasmic Reticulum ◽  
Endoplasmic Reticulum Membrane ◽  
Membrane Complex

scholarly journals Loss of primary cilia increases polycystin-2 and TRPV4 and the appearance of a nonselective cation channel in the mouse cortical collecting duct

2019 ◽  
Vol 317 (3) ◽  
pp. F632-F637 ◽  
Author(s):  
Takamitsu Saigusa ◽  
Qiang Yue ◽  
Marlene A. Bunni ◽  
P. Darwin Bell ◽  
Douglas C. Eaton
Keyword(s):  
Collecting Duct ◽  
Cation Channel ◽  
Conditional Knockout ◽  
Nonselective Cation Channel ◽  
Channel Activity ◽  
Open Probability ◽  
Duct Cells ◽  
Collecting Ducts ◽  
Collecting Duct Cells

Flow-related bending of cilia results in Ca2+ influx through a polycystin-1 (Pkd1) and polycystin-2 (Pkd2) complex, both of which are members of the transient receptor potential (TRP) family (TRPP1 and TRPP2, respectively). Deletion of this complex as well as cilia result in polycystic kidney disease. The Ca2+ influx pathway has been previously characterized in immortalized collecting duct cells without cilia and found to be a 23-pS channel that was a multimere of TRPP2 and TRPV4. The purpose of the present study was to determine if this TRPP2 and TRPV4 multimere exists in vivo. Apical channel activity was measured using the patch-clamp technique from isolated split-open cortical collecting ducts from adult conditional knockout mice with ( Ift88flox/flox) or without ( Ift88−/−) cilia. Single tubules were isolated for measurements of mRNA for Pkd1, Pkd2, Trpv4, and epithelial Na+ channel subunits. The predominant channel activity from Ift88flox/flox mice was from epithelial Na+ channel [5-pS Na+-selective channels with long mean open times (475.7 ± 83.26 ms) and open probability > 0.2]. With the loss of cilia, the predominant conductance was a 23-pS nonselective cation channel (reversal potential near 0) with a short mean open time (72 ± 17 ms), open probability < 0.08, and a characteristic flickery opening. Loss of cilia increased mRNA levels for Pkd2 and Trpv4 from single isolated cortical collecting ducts. In conclusion, 23-pS channels exist in vivo, and activity of this channel is elevated with loss of cilia, consistent with previous finding of an elevated-unregulated Ca2+-permeable pathway at the apical membrane of collecting duct cells that lack cilia.

Sec62p, A Component of the Endoplasmic Reticulum Protein Translocation Machinery, Contains Multiple Binding Sites for the Sec-Complex

2000 ◽  
Vol 11 (11) ◽  
pp. 3859-3871 ◽  
Author(s):  
Sandra Wittke ◽  
Martin Dünnwald ◽  
Nils Johnsson
Keyword(s):  
Endoplasmic Reticulum ◽  
Protein Translocation ◽  
Signal Sequence ◽  
Endoplasmic Reticulum Membrane ◽  
Sequence Recognition ◽  
Multiple Binding Sites ◽  
Oligomeric Protein ◽  
Multiple Binding ◽  
Endoplasmic Reticulum Protein

SEC62 encodes an essential component of the Sec-complex that is responsible for posttranslational protein translocation across the membrane of the endoplasmic reticulum in Saccharomyces cerevisiae. The specific role of Sec62p in translocation was not known and difficult to identify because it is part of an oligomeric protein complex in the endoplasmic reticulum membrane. An in vivo competition assay allowed us to characterize and dissect physical and functional interactions between Sec62p and components of the Sec-complex. We could show that Sec62p binds via its cytosolic N- and C-terminal domains to the Sec-complex. The N-terminal domain, which harbors the major interaction site, binds directly to the last 14 residues of Sec63p. The C-terminal binding site of Sec62p is less important for complex stability, but adjoins the region in Sec62p that might be involved in signal sequence recognition.

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