Long-lived plasma cells in the bone marrow produce memory antibodies that provide immune protection persisting for decades after infection or vaccination but can also contribute to autoimmune and ...allergic diseases. However, the composition of the microenvironmental niches that are important for the generation and maintenance of these cells is only poorly understood. Here, we demonstrate that, within the bone marrow, plasma cells interact with the platelet precursors (megakaryocytes), which produce the prominent plasma cell survival factors APRIL (a proliferation-inducing ligand) and IL-6 (interleukin-6). Accordingly, reduced numbers of immature and mature plasma cells are found in the bone marrow of mice deficient for the thrombopoietin receptor (c-mpl) that show impaired megakaryopoiesis. After immunization, accumulation of antigen-specific plasma cells in the bone marrow is disturbed in these mice. Vice versa, injection of thrombopoietin allows the accumulation and persistence of a larger number of plasma cells generated in the course of a specific immune response in wild-type mice. These results demonstrate that megakaryocytes constitute an important component of the niche for long-lived plasma cells in the bone marrow.
Patients with proteinuric kidney diseases often have symptoms of salt and water retention. It has been hypothesized that dysregulated sodium absorption is due to increased proteolytic cleavage of ...epithelial sodium channels (ENaCs) and increased Na,K-ATPase expression. Microarray analysis identified a reduction in kidney corin mRNA expression in rat models of puromycin aminonucleoside-induced nephrotic syndrome and acute anti-Thy1 glomerulonephritis (GN). As atrial natriuretic peptide (ANP) resistance is a mechanism accounting for volume retention, we analyzed the renal expression and function of corin; a type II transmembrane serine protease that converts pro-ANP to active ANP. Immunohistochemical analysis found that corin colocalized with ANP. The nephrotic and glomerulonephritic models exhibited concomitant increased pro-ANP and decreased ANP protein levels in the kidney consistent with low amounts of corin. Importantly, kidneys from corin knockout mice had increased amounts of renal β-ENaC and its activators, phosphodiesterase (PDE) 5 and protein kinase G II, when compared to wild-type mice. A similar expression profile was also found in cell culture suggesting the increase in PDE5 and kinase G II could account for the increase in β-ENaC seen in nephrotic syndrome and GN. Thus, we suggest that corin might be involved in the salt retention seen in glomerular diseases.
Intrarenal Renin Angiotensin System Revisited Pohl, Marcus; Kaminski, Henriette; Castrop, Hayo ...
Journal of biological chemistry/The Journal of biological chemistry,
12/2010, Letnik:
285, Številka:
53
Journal Article
Recenzirano
Odprti dostop
The existence of a local renin angiotensin system (RAS) of the kidney has been established. Angiotensinogen (AGT), renin, angiotensin-converting enzyme (ACE), angiotensin receptors, and high ...concentrations of luminal angiotensin II have been found in the proximal tubule. Although functional data have documented the relevance of a local RAS, the dualism between biosynthesis and endocytotic uptake of its components and their cellular processing has been incompletely understood. To resolve this, we have selectively analyzed their distribution, endocytosis, transcytosis, and biosynthesis in the proximal tubule. The presence of immunoreactive AGT, restricted to the early proximal tubule, was due to its retrieval from the ultrafiltrate and storage in endosomal and lysosomal compartments. Cellular uptake was demonstrated by autoradiography of radiolabeled AGT and depended on intact endocytosis. AGT was identified as a ligand of the multiple ligand-binding repeats of megalin. AGT biosynthesis was restricted to the proximal straight tubule, revealing substantial AGT mRNA expression. Transgenic AGT overexpression under the control of an endogenous promoter was also restricted to the late proximal tubule. Proximal handling of renin largely followed the patterns of AGT, whereas its local biosynthesis was not significant. Transcytotic transport of AGT in a proximal cell line revealed a 5% recovery rate after 1 h. ACE was expressed along late proximal brush-border membrane, whereas ACE2 was present along the entire segment. Surface expression of ACE and ACE2 differed as a function of endocytosis. Our data on the localization and cellular processing of RAS components provide new aspects of the functional concept of a “self-contained” renal RAS.
The existence of a local renin angiotensin system (RAS) of the kidney has been established. Angiotensinogen (AGT), renin, angiotensin-converting enzyme (ACE), angiotensin receptors, and high ...concentrations of luminal angiotensin II have been found in the proximal tubule. Although functional data have documented the relevance of a local RAS, the dualism between biosynthesis and endocytotic uptake of its components and their cellular processing has been incompletely understood. To resolve this, we have selectively analyzed their distribution, endocytosis, transcytosis, and biosynthesis in the proximal tubule. The presence of immunoreactive AGT, restricted to the early proximal tubule, was due to its retrieval from the ultrafiltrate and storage in endosomal and lysosomal compartments. Cellular uptake was demonstrated by autoradiography of radiolabeled AGT and depended on intact endocytosis. AGT was identified as a ligand of the multiple ligand-binding repeats of megalin. AGT biosynthesis was restricted to the proximal straight tubule, revealing substantial AGT mRNA expression. Transgenic AGT overexpression under the control of an endogenous promoter was also restricted to the late proximal tubule. Proximal handling of renin largely followed the patterns of AGT, whereas its local biosynthesis was not significant. Transcytotic transport of AGT in a proximal cell line revealed a 5% recovery rate after 1 h. ACE was expressed along late proximal brush-border membrane, whereas ACE2 was present along the entire segment. Surface expression of ACE and ACE2 differed as a function of endocytosis. Our data on the localization and cellular processing of RAS components provide new aspects of the functional concept of a "self-contained" renal RAS.
Abstract only
Transport activity of the thick ascending limb (TAL) Na(+)K(+)2Cl(−) cotransporter (NKCC2) critically depends on its association with lipid raft membrane microdomains (LR). Aim of the ...present study was to characterize the protein composition of NKCC2‐containing LR. To this end we isolated detergent‐resistant LR from rat renal outer medullary tissue samples using a discontinuous sucrose gradient and ultracentrifugation (floating assay). NKCC2‐containing LR were purified from total LR by immunoprecipitation. Protein content of the precipitates was analyzed by western blot and mass spectrometry (MS). Floating assay confirmed accumulation of NKCC2 in LR‐enriched fractions. Analysis of the immunoprecipitate demonstrated the presence of NKCC2 and, among others, the lipid raft proteins flotillin‐1 and annexin A2. In conclusion, we have successfully established a protocol for the isolation of NKCC2‐containing LR from kidney samples. Further analysis of the protein content of these LR may provide insight into the regulation of NKCC2 function.
Support: DFG FOR667
Abstract only
Annexin A2 has been shown to act as a receptor for plasminogen (Plg) and its tissue type activator (tPA) in endothelial cells (EC). Aim of the present study was to elucidate the renal ...distribution of the components of this complex under control conditions and in a Thy1 nephritis model of proteinuric renal disease. Thy1 nephritis was induced by intravenous injection of OX7 anti‐Thy1 antibody (1mg/kg body weight). Distribution of Plg, tPA and ANXA2 was studied by immunofluorescence in controls and after 5 or 15 days of OX7 injection. Immunoreactive structures were further characterized by double‐labeling immunofluorescence using antibodies against rat endothelial cell antigen for EC, Na(+),K(+),2Cl(−) cotransporter for thick ascending limbs (TAL), aquaporin‐1 for thin descending limbs (tDL) and aquaporin‐2 for collecting ducts (CD). As expected, all three proteins were identified in EC of controls and Thy1 animals. In addition we found overlapping signal for tPA, Plg and ANXA2 in the basolateral and apical membrane of tDL, TAL and CD both, in treated and untreated animals. Furthermore, abundance of tPA and Plg in the apical membrane of TAL and CD was increased in proteinuric animals. In conclusion, our results provide evidence for the presence of a proteolytic complex in the apical membrane of renal epithelia where it may play a protective role in the setting of proteinuric disease.
support: DFG FOR 667
In the present study we aimed to elucidate the effects of chronic vasopressin (AVP) administration on renal medullary oxygen levels in AVP‐deficient Brattleboro rats (DI rats). To this end, adult DI ...rats were treated for 3 days with the V2 AVP receptor agonist desmopressin (dDAVP, 5ng/h; 3d) or its vehicle via osmotic minipump. Pimonidazole immunostaining was employed to study oxygen distribution throughout the kidney. In addition, outer medullary gene expression was determined by microarray analysis. dDAVP treatment resulted in a significant drop in urine output (−94 +/− 24% compared to controls, p < .05). Pimonidazole staining was detected in medullary rays of the cortex and in the outer as well as in the inner medulla of dDAVP‐treated rats whereas signal in control animals was weak or absent. Gene expression analysis revealed an upregulation of several known target genes for hypoxia‐inducible factors which included hexokinase 2, phosphofructokinase, heme oxygenase 1, insulin like growth factor (IGF) 1 and IGF binding proteins 1 and 3. Our results suggest that an activation of the renal urine concentration mechanism by dDAVP causes renal medullary hypoxia and an upregulation of hypoxia‐inducible target gene expression.
This study was supported by the German Research Foundation (FOR 667)
Aim of the present study was to elucidate the renal expression pattern of Annexin A2 (ANXA2) during steady state and during activation of the urine concentration mechanism. To this end, adult ...Brattleboro rats (DI rats) were treated for 3d with the selective V2 vasopressin receptor agonist desmopressin (dDAVP, 5ng/h) or vehicle via osmotic minipump. Renal ANXA2 distribution was studied by double‐labelling immunofluorescence using two different antibodies against ANXA2 and antibodies against rat endothelial cell antigen for endothelial cells, Tamm‐Horsfall protein for thick ascending limbs (TAL) and aquaporin‐2 for collecting ducts (CD). In untreated DI rats strong ANXA2 immunoreactivity was detected in cells of the Bowman capsule and in endothelial cells. Cells of the CD showed intermediate staining throughout the cytosol. In addition we observed a weak but consistent ANXA2 signal in the apical membrane of TAL profiles. Treatment of DI rats with dDAVP caused a marked shift of ANXA2 protein from the cytosol of CD cells to the apical and the basolateral membrane. In summary, we have shown that ANXA2 is expressed in cells of the Bowman capsule, the renal endothelium, the TAL and in the collecting duct where it may be involved in vasopressin signalling.
This study was supported by the German Research Foundation (FOR 667).
Patients with proteinuric kidney diseases often experience symptoms of salt and water retention. It has been hypothesized that the dysregulated Na
+
absorption is due to increased proteolytic ...cleavage of epithelial sodium channel (ENaC) and increased Na,K-ATPase expression. Microarray analysis identified a reduced corin mRNA expression in kidneys from rat models of puromycin aminonucleoside-induced nephrotic syndrome (PAN) and acute anti-Thy1 glomerulonephritis (GN). Corin has been shown to convert pro-atrial natriuretic peptide (ANP) to ANP. Because ANP resistance has been assumed to be a mechanism accounting for volume retention, experiments were undertaken to analyze the renal expression and function of corin. Immunohistochemistry revealed that corin co-localized with ANP. In PAN and GN, kidneys exhibited concomitant increased pro-ANP and decreased ANP protein expression levels consistent with low corin levels. Importantly, kidneys from corin −/− mice showed increased levels of renal β-ENaC, phosphodiesterase 5 (PDE5) and protein kinase G II (PKGII) when compared to wild-type mice. Similar expression profile was observed in cell culture experiments suggesting that the increase in PDE5 and PKGII could account for the increase in β-ENaC as observed in PAN and GN.
To conclude, our data provide novel insights into the mechanisms of volume retention in renal disease with corin as an important new mediator that acts through PKGII induction and ENaC activation.
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