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A well-developed endolysosomal system reflects protein reabsorption in segment 1 and 2 of rat proximal tubules

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A well-developed endolysosomal system reflects protein reabsorption in segment 1 and 2 of rat proximal tubules. / Christensen, Erik I; Kristoffersen, Inger B; Grann, Birgitte; Thomsen, Jesper S; Andreasen, Arne; Nielsen, Rikke.

I: Kidney International, Bind 99, Nr. 4, 04.2021, s. 841-853.

Publikation: Bidrag til tidsskrift/Konferencebidrag i tidsskrift /Bidrag til avisTidsskriftartikelForskningpeer review

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@article{65e38aab26d145c090a7299da3fcf648,
title = "A well-developed endolysosomal system reflects protein reabsorption in segment 1 and 2 of rat proximal tubules",
abstract = "Proteinuria is a well-established marker and predictor of kidney disease. The receptors megalin and cubilin reabsorb filtered proteins and thereby proteinuria is avoided. It is unknown if all segments of the proximal tubule are involved in clearing the filtrate or if there exists a reserve capacity in case of increased glomerular protein filtration. To determine this, we performed serial sectioning of rat kidney and used stereology to quantify the endolysosomal system of the three segments of cortical and juxtamedullary nephrons by electron microscopy. Immunohistochemistry was applied to analyze the adaptor protein Dab2, which assists in megalin mediated endocytosis, megalin, and endocytic uptake of two endogenous megalin ligands; retinol binding protein and β2-microglobulin at exact tubular positions. Proteinuric rats (puromycin-treated) and mice (podocin knock-out) were analyzed to clarify the response of the tubule to increased protein filtration. We found that the endolysosomal system was most prominent in segment 1 and 2, whereas segment 3 was less developed. The depth of ligand uptake varied among nephrons, but it descended into segment 2 although uptake was lower than in segment 1 and it was never observed in segment 3. This was supported by prominent expression of Dab2 in segment 1 and 2. When protein filtration increased, segment 3 was included in the reabsorption process in proteinuric animals. Thus, segment 1 and 2 are responsible for clearing the filtrate for protein during normal physiological conditions, but the tubule exhibits plasticity and is able to include segment 3 under proteinuric stress.",
author = "Christensen, {Erik I} and Kristoffersen, {Inger B} and Birgitte Grann and Thomsen, {Jesper S} and Arne Andreasen and Rikke Nielsen",
note = "Copyright {\textcopyright} 2020. Published by Elsevier Inc.",
year = "2021",
month = apr,
doi = "10.1016/j.kint.2020.11.015",
language = "English",
volume = "99",
pages = "841--853",
journal = "Kidney International. Supplement",
issn = "0098-6577",
publisher = "Wiley-Blackwell Publishing, Inc.",
number = "4",

}

RIS

TY - JOUR

T1 - A well-developed endolysosomal system reflects protein reabsorption in segment 1 and 2 of rat proximal tubules

AU - Christensen, Erik I

AU - Kristoffersen, Inger B

AU - Grann, Birgitte

AU - Thomsen, Jesper S

AU - Andreasen, Arne

AU - Nielsen, Rikke

N1 - Copyright © 2020. Published by Elsevier Inc.

PY - 2021/4

Y1 - 2021/4

N2 - Proteinuria is a well-established marker and predictor of kidney disease. The receptors megalin and cubilin reabsorb filtered proteins and thereby proteinuria is avoided. It is unknown if all segments of the proximal tubule are involved in clearing the filtrate or if there exists a reserve capacity in case of increased glomerular protein filtration. To determine this, we performed serial sectioning of rat kidney and used stereology to quantify the endolysosomal system of the three segments of cortical and juxtamedullary nephrons by electron microscopy. Immunohistochemistry was applied to analyze the adaptor protein Dab2, which assists in megalin mediated endocytosis, megalin, and endocytic uptake of two endogenous megalin ligands; retinol binding protein and β2-microglobulin at exact tubular positions. Proteinuric rats (puromycin-treated) and mice (podocin knock-out) were analyzed to clarify the response of the tubule to increased protein filtration. We found that the endolysosomal system was most prominent in segment 1 and 2, whereas segment 3 was less developed. The depth of ligand uptake varied among nephrons, but it descended into segment 2 although uptake was lower than in segment 1 and it was never observed in segment 3. This was supported by prominent expression of Dab2 in segment 1 and 2. When protein filtration increased, segment 3 was included in the reabsorption process in proteinuric animals. Thus, segment 1 and 2 are responsible for clearing the filtrate for protein during normal physiological conditions, but the tubule exhibits plasticity and is able to include segment 3 under proteinuric stress.

AB - Proteinuria is a well-established marker and predictor of kidney disease. The receptors megalin and cubilin reabsorb filtered proteins and thereby proteinuria is avoided. It is unknown if all segments of the proximal tubule are involved in clearing the filtrate or if there exists a reserve capacity in case of increased glomerular protein filtration. To determine this, we performed serial sectioning of rat kidney and used stereology to quantify the endolysosomal system of the three segments of cortical and juxtamedullary nephrons by electron microscopy. Immunohistochemistry was applied to analyze the adaptor protein Dab2, which assists in megalin mediated endocytosis, megalin, and endocytic uptake of two endogenous megalin ligands; retinol binding protein and β2-microglobulin at exact tubular positions. Proteinuric rats (puromycin-treated) and mice (podocin knock-out) were analyzed to clarify the response of the tubule to increased protein filtration. We found that the endolysosomal system was most prominent in segment 1 and 2, whereas segment 3 was less developed. The depth of ligand uptake varied among nephrons, but it descended into segment 2 although uptake was lower than in segment 1 and it was never observed in segment 3. This was supported by prominent expression of Dab2 in segment 1 and 2. When protein filtration increased, segment 3 was included in the reabsorption process in proteinuric animals. Thus, segment 1 and 2 are responsible for clearing the filtrate for protein during normal physiological conditions, but the tubule exhibits plasticity and is able to include segment 3 under proteinuric stress.

U2 - 10.1016/j.kint.2020.11.015

DO - 10.1016/j.kint.2020.11.015

M3 - Journal article

C2 - 33340516

VL - 99

SP - 841

EP - 853

JO - Kidney International. Supplement

JF - Kidney International. Supplement

SN - 0098-6577

IS - 4

ER -