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The soluble intracellular domain of megalin does not affect renal proximal tubular function in vivo

ABSTRACT: The endocytic receptor megalin constitutes the main pathway for clearance of plasma proteins from the glomerular filtrate in the proximal tubules. However, little is know about the mechanisms that control receptor activity. A widely discussed hypothesis states that the intracellular domain (ICD) of megalin, released upon ligand binding, acts as a transcription regulator to suppress receptor expression - a mechanism proposed to safeguard the proximal tubules from protein overload. Here, we have put this hypothesis to the test by generating a mouse model co-expressing the soluble ICD and the full-length receptor. Despite pronounced expression in the proximal tubules, the ICD failed to exert any effects on renal proximal tubular function such as megalin expression, protein retrieval, or renal gene transcription. Thus, our data argue that the ICD does not play a role in regulation of megalin activity in vivo in the proximal tubules. We used microarrays to compare gene expression profile in adult kidney from a new mouse model expressing the intracellular domain of megalin with wildtype.

ORGANISM(S): Mus musculus

PROVIDER: GSE19778 | GEO | 2011/01/01

SECONDARY ACCESSION(S): PRJNA121863

REPOSITORIES: GEO

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The soluble intracellular domain of megalin does not affect renal proximal tubular function in vivo

Project description:The endocytic receptor megalin constitutes the main pathway for clearance of plasma proteins from the glomerular filtrate in the proximal tubules. However, little is know about the mechanisms that control receptor activity. A widely discussed hypothesis states that the intracellular domain (ICD) of megalin, released upon ligand binding, acts as a transcription regulator to suppress receptor expression - a mechanism proposed to safeguard the proximal tubules from protein overload. Here, we have put this hypothesis to the test by generating a mouse model co-expressing the soluble ICD and the full-length receptor. Despite pronounced expression in the proximal tubules, the ICD failed to exert any effects on renal proximal tubular function such as megalin expression, protein retrieval, or renal gene transcription. Thus, our data argue that the ICD does not play a role in regulation of megalin activity in vivo in the proximal tubules. We used microarrays to compare gene expression profile in adult kidney from a new mouse model expressing the intracellular domain of megalin with wildtype. 10 week old mice were collected for RNA extraction and hybridization on Affymetrix microarrays. Three individuals for each genotype were analyzed comparing heterozygous animals for the intracellular domain of megalin with littermates controls.

2011-01-01 | E-GEOD-19778 | biostudies-arrayexpress

TMAO Suppresses Megalin Expression and Albumin Uptake in Human Proximal Tubular Cells Via PI3K and ERK Signaling

Project description:Trimethylamine-N-oxide (TMAO) is a uremic toxin, which has been associated with chronic kidney disease (CKD). Renal tubular epithelial cells play a central role in the pathophysiology of CKD. Megalin is an albumin-binding surface receptor on tubular epithelial cells, which is indispensable for urine protein reabsorption. To date, no studies have investigated the effect of TMAO on megalin expression and the functional properties of human tubular epithelial cells. The aim of this study was first to identify the functional effect of TMAO on human renal proximal tubular cells and second, to unravel the effects of TMAO on megalin-cubilin receptor expression. We found through global gene expression analysis that TMAO was associated with kidney disease. The microarray analysis also showed that megalin expression was suppressed by TMAO, which was also validated at the gene and protein level. High glucose and TMAO was shown to downregulate megalin expression and albumin uptake similarly. We also found that TMAO suppressed megalin expression via PI3K and ERK signaling. Furthermore, we showed that candesartan, dapagliflozin and enalaprilat counter-acted the suppressive effect of TMAO on megalin expression. Our results may further help us un-ravel the role of TMAO in CKD development and to identify new therapeutic targets to counteract TMAOs effects.

2022-08-10 | GSE210692 | GEO

Cubilin-, Megalin- and Dab2-dependent transcription revealed by CRISPR/Cas9 knockout in kidney proximal tubule cells

Project description:The multiligand receptor megalin and its endocytic adaptor protein Dab2 play essential roles in maintaining the integrity of the apical endocytic pathway of proximal tubule cells, and have complex and poorly understood roles in the development of chronic kidney disease. Here we used RNASeq in CRISPR/Cas9 knockout technology in a well-differentiated cell culture model to identify PT-specific transcriptional changes that are directly consequent to the loss of megalin (Lrp2), cubilin (Cubn), or Dab2 (Dab2) expression.

2021-12-29 | GSE176090 | GEO

Transcription profiling of gonads from E14.5 megalin+/+ and megalin-/- embryos

Project description:Presently, genes regulated by steroid hormones during induced regression of the CSL (cranial suspensory ligament) are unknown. To identify such genes and to evaluate their expression levels in megalin-deficient mice, we performed global gene expression profiling on gonads from E14.5 megalin+/+ and megalin-/- embryos.

2005-06-30 | E-MEXP-352 | biostudies-arrayexpress

Severe kidney dysfunction in sialidosis mice reveals an essential role for neuraminidase 1 in reabsorption

Project description:Sialidosis is an ultrarare multisystemic lysosomal disease caused by mutations in the neuraminidase 1 (NEU1) gene. The severe Type II form of the disease, manifests with a prenatal/infantile or juvenile onset, bone abnormalities, severe neuropathology and visceromegaly. A subset of these patients presents with nephrosialidosis, characterized by abrupt onset of fulminant glomerular nephropathy. We studied the pathophysiological mechanism of the disease in two NEU1-deficient mouse models, a constitutive Neu1 knockout Neu1ΔEx3 and a conditional phagocyte-specific knockout Neu1Cx3cr1ΔEx3. Mice of both strains exhibited terminal urinary retention and severe kidney damage with elevated urinary albumin levels, loss of nephrons, renal fibrosis, presence of storage vacuoles and dysmorphic mitochondria in the intraglomerular and tubular cells. Glycoprotein sialylation in glomeruli, proximal and distal tubules was drastically increased including that of an endocytic reabsorption receptor megalin. The pool of megalin bearing O-linked glycans with terminal galactose residues, essential for protein targeting and activity, was reduced to below detection levels. Megalin levels were severely reduced, and the protein was directed to lysosomes instead of the apical membrane. Together, our results demonstrated that desialylation by NEU1 plays a crucial role in processing and cellular trafficking of megalin and that NEU1 deficiency in sialidosis impairs megalinmediated protein reabsorption.

2024-01-26 | PXD044833 | Pride

Gene expression profiles in isolated proximal tubules and whole kidneys of rats after cisplatin-administration

Project description:To clarify the effects of cisplatin (cis-diamminedichloroplatinum II, CDDP) on the gene expression profiles in renal proximal tubules, microarray analyses were carried out using total RNA samples isolated from microdissected proximal tubules and whole kidneys. The molecular events underlying acute kidney injury (AKI) in the proximal tubules of rats with cisplatin-induced nephrotoxicity were successfully clarified with 17,000 transcripts. Renal proximal tubules were isolated under microscopy, and transcriptome data were collected with Rat Genome Survey MicroarrayÂ® (Applied Biosystems)

2013-12-24 | E-GEOD-37133 | biostudies-arrayexpress

Mus musculus

Project description:The soluble intracellular domain of megalin does not affect renal proximal tubular function in vivo

| PRJNA121863 | ENA

Peroxisomes are dispensable for normal renal function.

Project description:Peroxisomes are highly abundant in proximal tubules where peroxisomal enzymes have been proposed to play an important role in a variety of metabolic and antioxidant functions. This hypothesis was supported by human genetic studies that identified mutations leading to peroxisomal biogenesis deficiency, resulting in severe multi-organ damage (Zellweger’s spectrum disorders (ZSD)), including renal impairment. However, the role of proximal tubule peroxisomes in renal (patho)physiology remains uninvestigated. We addressed this question in mice with conditional ablation of peroxisomal biogenesis in the renal tubule. Our results demonstrate that renal tubular peroxisomes are dispensable for normal renal function and suggest that renal damage in ZSD patients is of extrarenal origin.

2022-03-02 | GSE179202 | GEO

Transcriptional profiling of the zebrafish proximal tubule

Project description:The proximal tubules of the kidney carry out the bulk of solute reabsorption from the glomerular filtrate. They are also highly susceptible to damage as a result of diabetes or other syndromes that affect the kidney. The zebrafish embryonic/larval form of kidney, the pronephros, represents a simplified form of the mammalian organ, yet is easier to access and manipulate. We have recently described the importance of Hnf1b as master regulator in pronephros differentiation. Here, we establish a high-resolution expression profile of isolated, GFP-labelled proximal tubules from 3-day-old zebrafish. To enrich the profile in genes of functional relevance during pronephros differentiation, proximal tubules from Hnf1b-depleted larvae were analysed in parallel and differential expression analysis was performed.

2019-06-05 | GSE95808 | GEO

AFFYMETRIX ANALYSIS OF E9.5 RFC MOUSE KO EMBRYOS REVEALS ALTERED EXPR’N OF GENES IN THE CUBILIN-MEGALIN COMPLEX

Project description:The reduced folate carrier (RFC1) is an integral membrane protein and facilitative anion exchanger that mediates delivery of 5-methyltetrahydrofolate into mammalian cells. Adequate maternal-fetal transport of folate is necessary for normal embryogenesis. Targeted inactivation of the murine RFC1 gene results in post-implantation embryo lethality, but daily folic acid supplementation of pregnant dams prolongs survival of homozygous embryos until mid-gestation. At E10.5 RFC1-/- embryos are developmentally delayed relative to wildtype littermates, have multiple malformations, including neural tube defects, and die due to failure of chorioallantoic fusion. The mesoderm is sparse and disorganized, and there is a marked absence of erythrocytes in yolk sac blood islands. Affymetrix microarray analysis and quantitative RT-PCR validation of the relative gene expression profiles in E9.5 RFC1-/- vs. RFC1+/+ embryos indicates a dramatic downregulation of multiple genes involved in erythropoiesis, and upregulation of several genes that form the cubilin-megalin multiligand endocytic receptor complex. Megalin protein expression disappears from the visceral yolk sac of RFC1-/- embryos, and cubilin protein is widely misexpressed. Inactivation of RFC1 impacts the expression of several ligands and interacting proteins in the cubilin-amnionless-megalin complex that are involved in the maternal-fetal transport of folate, vitamin B12, and other nutrients, lipids and morphogens required for normal embryogenesis. Comparison of RFC KO, wildtype normal embryos vs. RFC KO, nullizygous affected embryos Keywords: reduced folate carrier knockout, folate receptor, cubilin, megalin, embryos, gene expression, neural tube defect, chorioallantoic fusion

2008-03-17 | GSE10659 | GEO

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