Albumin endocytosis in OK cells: dependence on actin and microtubules and regulation by protein kinases

Gekle, Michael; Mildenberger, Sigrid; Freudinger, Ruth; Schwerdt, Gerald; Silbernagl, S.

doi:10.1152/ajprenal.1997.272.5.f668

Cited by 60 publications

(96 citation statements)

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“…Both kinases inhibit albumin endocytosis through the modulation of a different step in endocytosis. For example, PKA modulates the early phase whereas PKC modulates the late phase of endocytosis (1,28). In our studies, the maximal effect of Ang II to stimulate endocytosis was observed after 3 h of preincubation, indicating that it takes several hours to elicit the full effect of Ang II on the signal transduction pathways regulating albumin endocytosis.…”

Section: Discussionmentioning

confidence: 53%

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Albumin endocytosis in proximal tubule cells is modulated by angiotensin II through an AT ₂ receptor-mediated protein kinase B activation

Caruso-Neves

Kwon

Guggino

2005

Proc. Natl. Acad. Sci. U.S.A.

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Albumin endocytosis in renal proximal tubule cells is a clathrin-and receptor-mediated mechanism that, in several pathophysiological conditions, is involved in initiating or promoting tubule-interstitial disease. Although much work has been done on this pathway, the regulation of albumin endocytosis in proximal tubule cells is not well understood. Here, we study the modulation by angiotensin II (Ang II) of albumin endocytosis in LLC-PK1, a model of proximal tubule cells. We observed that Ang II increases albumin endocytosis by Ϸ100% at 10 ؊9 M. This effect is completely reversed by 10 ؊9 M PD123319, a specific AT2 receptor antagonist, but not by losartan, a specific AT1 receptor antagonist, at concentrations up to 10 ؊7 M. The Ang II effect on albumin endocytosis is also reversed by: phosphoinositide 3-kinase inhibitors LY294002 (2.5 ؋ 10 ؊6 M) or wortmannin (10 ؊7 M), the protein kinase B inhibitor (2 ؋ 10 ؊5 M), and staurosporine (2 ؋ 10 ؊6 M), an inhibitor of 3 -phosphoinositide-dependent kinase 1. Ang II induced the selective phosphorylation of protein kinase B (PKB) at the Thr-308 residue without a change in Ser-473 phosphorylation, a combination that leads to an increase in PKB activity. These effects were completely abolished by 3 ؋ 10 ؊6 M staurosporine or 10 ؊8 M PD123319. Our experiments also showed that PKB is present in the membrane fraction in overnight-starved LLC-PK1 cells. Taken together, these data show that Ang II increases albumin endocytosis through an AT2 receptor mediated by activation of PKB in the plasma membrane, which depends on the basal activity of the phosphatidylinositol 3-kinase.kidney ͉ reabsorption ͉ regulation

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Section: Discussionmentioning

confidence: 53%

“…Other proteins belonging to AGC kinases family, such as protein kinase A (PKA) and protein kinase C (PKC), modulate albumin endocytosis in OK cells (1,28). Both kinases inhibit albumin endocytosis through the modulation of a different step in endocytosis.…”

Section: Discussionmentioning

confidence: 99%

Albumin endocytosis in proximal tubule cells is modulated by angiotensin II through an AT ₂ receptor-mediated protein kinase B activation

Caruso-Neves

Kwon

Guggino

2005

Proc. Natl. Acad. Sci. U.S.A.

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“…Several stable cell lines derived from proximal tubules are available to study the process of protein reabsorption in tissue culture. These include the opossum kidney cell line (OK), which retains characteristics of proximal tubular epithelial cells, particularly a high rate of uptake of albumin by endocytosis (20), and has been used to study the mechanisms and regulation of protein endocytosis (21)(22)(23).…”

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confidence: 99%

Inhibitors of 3-Hydroxy-3-Methylglutaryl–CoA Reductase Reduce Receptor-Mediated Endocytosis in Opossum Kidney Cells

Sidaway¹,

Davidson

McTaggart

et al. 2004

Journal of the American Society of Nephrology

140

105

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Abstract. Renal proximal tubule cells are responsible for the reabsorption of proteins that are present in the tubular lumen. This occurs by receptor-mediated endocytosis, a process that has a requirement for some GTP-binding proteins. Statins are inhibitors of 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase used for the therapeutic reduction of cholesterol-containing plasma lipoproteins. However, they can also reduce intracellular levels of isoprenoid pyrophosphates that are derived from the product of the enzyme, mevalonate, and are required for the prenylation and normal function of GTP-binding proteins. The hypothesis that inhibition of HMG-CoA reductase in renal proximal tubule cells could reduce receptor mediated-endocytosis was therefore tested. Five different statins inhibited the uptake of FITC-labeled albumin by the proximal tubule-derived opossum kidney cell line in a dose-dependent manner and in the absence of cytotoxicity. The reduction in albumin uptake was related to the degree of inhibition of HMG-CoA reductase. Simvastatin (e.g., statin) inhibited receptor-mediated endocytosis of both FITC-albumin and FITC-␤ 2 -microglobulin to similar extents but without altering the binding of albumin to the cell surface. The effect on albumin endocytosis was prevented by mevalonate and by the isoprenoid geranylgeranyl pyrophosphate but not by cholesterol. Finally, evidence that the inhibitory effect of statins on endocytosis of proteins may be caused by reduced prenylation and thereby decreased function of one or more GTP-binding proteins is provided. These data establish the possibility in principle that inhibition of HMG-CoA reductase by statins in proximal tubule cells may reduce tubular protein reabsorption.Statins are inhibitors of the enzyme 3-hydroxy-3-methylglutaryl CoA (HMG-CoA) reductase, which catalyzes the conversion of HMG-CoA to mevalonate, the major rate-limiting step of the sterol pathway (1). The statins are widely used for the therapeutic reduction of cholesterol-containing atherogenic lipoproteins (2-4). This is brought about as a result of depletion of intracellular mevalonate leading to reduction of the regulatory sterol pool, which in turn causes upregulation of HMGCoA reductase and other enzymes of the sterol pathway, most importantly the LDL receptors principally in the liver (5-7). However, a range of additional effects of statins on cells that are independent of cholesterol homeostasis has been described; these include, proliferation (8), signal transduction (9), and apoptosis (10). Many of these cholesterol-independent effects of statins have been shown to result from depletion of mevalonate and its nonsterol metabolites, particularly the isoprenoid pyrophosphates, such as farnesol pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP), that are required for the posttranslation modification of a variety of cell proteins, including the superfamily of small GTP-binding proteins (11)(12)(13). Endocytosis is one cell function that requires multiple GTP-binding proteins (14,15) a...

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“…This hypothesis is supported by data from the proximal tubules of ClC-5 knock-out mice and patients with Dent's disease where megalin is down-regulated and the v-H ϩ -ATPase is mistrafficked to the basolateral domain (18,19). It is also clear that albumin uptake involves actin cytoskeleton acting as an anchoring point for the endocytic complex (20 -22), because disruption of the cytoskeleton abolishes albumin uptake (21,23). The presence of albumin causes actin clusters to form at the apical membrane that colocalize with the sites of albumin uptake (21).…”

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confidence: 84%

Regulation of Albumin Endocytosis by PSD95/Dlg/ZO-1 (PDZ) Scaffolds

Hryciw

Ekberg

Ferguson

et al. 2006

Journal of Biological Chemistry

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The constitutive reuptake of albumin from the glomerular filtrate by receptor-mediated endocytosis is a key function of the renal proximal tubules. Both the Cl ؊ channel ClC-5 and the Na ؉ -H ؉ exchanger isoform 3 are critical components of the macromolecular endocytic complex that is required for albumin uptake, and therefore the cell-surface levels of these proteins may limit albumin endocytosis. This study was undertaken to investigate the potential roles of the epithelial PDZ scaffolds, Na ؉ -H ؉ exchange regulatory factors, NHERF1 and NHERF2, in albumin uptake by opossum kidney (OK) cells. We found that ClC-5 co-immunoprecipitates with NHERF2 but not NHERF1 from OK cell lysate. Experiments using fusion proteins demonstrated that this was a direct interaction between an internal binding site in the C terminus of ClC-5 and the PDZ2 module of NHERF2. In OK cells, NHERF2 is restricted to the intravillar region while NHERF1 is located in the microvilli. Silencing NHERF2 reduced both cell-surface levels of ClC-5 and albumin uptake. Conversely, silencing NHERF1 increased cell-surface levels of ClC-5 and albumin uptake, presumably by increasing the mobility of NHE3 in the membrane and its availability to the albumin uptake complex. Surface biotinylation experiments revealed that both NHERF1 and NHERF2 were associated with the plasma membrane and that NHERF2 was recruited to the membrane in the presence of albumin. The importance of the interaction between NHERF2 and the cytoskeleton was demonstrated by a significant reduction in albumin uptake in cells overexpressing an ezrin binding-deficient mutant of NHERF2. Thus NHERF1 and NHERF2 differentially regulate albumin uptake by mechanisms that ultimately alter the cell-surface levels of ClC-5.

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Albumin endocytosis in OK cells: dependence on actin and microtubules and regulation by protein kinases

Cited by 60 publications

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Albumin endocytosis in proximal tubule cells is modulated by angiotensin II through an AT ₂ receptor-mediated protein kinase B activation

Albumin endocytosis in proximal tubule cells is modulated by angiotensin II through an AT ₂ receptor-mediated protein kinase B activation

Inhibitors of 3-Hydroxy-3-Methylglutaryl–CoA Reductase Reduce Receptor-Mediated Endocytosis in Opossum Kidney Cells

Regulation of Albumin Endocytosis by PSD95/Dlg/ZO-1 (PDZ) Scaffolds

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Albumin endocytosis in OK cells: dependence on actin and microtubules and regulation by protein kinases

Cited by 60 publications

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Albumin endocytosis in proximal tubule cells is modulated by angiotensin II through an AT 2 receptor-mediated protein kinase B activation

Albumin endocytosis in proximal tubule cells is modulated by angiotensin II through an AT 2 receptor-mediated protein kinase B activation

Inhibitors of 3-Hydroxy-3-Methylglutaryl–CoA Reductase Reduce Receptor-Mediated Endocytosis in Opossum Kidney Cells

Regulation of Albumin Endocytosis by PSD95/Dlg/ZO-1 (PDZ) Scaffolds

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Albumin endocytosis in proximal tubule cells is modulated by angiotensin II through an AT ₂ receptor-mediated protein kinase B activation

Albumin endocytosis in proximal tubule cells is modulated by angiotensin II through an AT ₂ receptor-mediated protein kinase B activation