The Experts below are selected from a list of 264 Experts worldwide ranked by ideXlab platform
Rajiv Kumar - One of the best experts on this subject based on the ideXlab platform.
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Vasopressin Receptor-Mediated Endocytosis in cells transfected with V1-type vasopressin receptors
Kidney International, 1993Co-Authors: Ward Lutz, Mark A. Sanders, Jeffrey L. Salisbury, Stephen Lolait, Anne Marie O'carroll, Rajiv KumarAbstract:Vasopressin Receptor-Mediated Endocytosis in cells transfected with V 1 -type vasopressin receptors. We examined the process of Receptor-Mediated Endocytosis in A-9 lung fibroblast and chinese hamster ovary (CHO) cells transfected with the recently cloned vasopressin V 1a receptor (51). We used a fluorescent labeled vasopressin analog (rho-damine-mercaptopropionic acid lysine vasopressin) and radiolabeled vasopressin to examine this process in the two transfected cell lines. Both A-9 and CHO cells internalize vasopressin in a manner consistent with Receptor-Mediated Endocytosis. A-9 cells internalize vasopressin more rapidly than CHO cells. The process is inhibited by vasopressin and by specific vasopressin V 1 receptor antagonists but not by specific V 2 receptor antagonists. Hypertonic sucrose inhibits Endocytosis in both cell types suggesting a role of clathrin coated pits in the Endocytosis of receptor in these cells. These cells are excellent models in which to examine the effect of receptor mutations on vasopressin Receptor-Mediated Endocytosis.
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Vasopressin Receptor-Mediated Endocytosis: current view
American Journal of Physiology-Renal Physiology, 1991Co-Authors: Ward Lutz, Jeffrey L. Salisbury, Rajiv KumarAbstract:A number of peptide hormones have been shown to undergo Receptor-Mediated Endocytosis (RME). RME involves the internalization of receptor-ligand complexes followed by delivery to an intracellular compartment, the endosome, from which ligands or receptors can be delivered to lysosomes or other cellular destinations. Vasopressin, a peptide hormone that plays a role in kidney and vascular physiology, has recently been demonstrated to undergo RME in LLC-PK1 and A10 cells, which express V2- and V1-type vasopressin receptors, respectively. Fluorescent vasopressin analogues are internalized by RME from the basolateral surface of polarized LLC-PK1 cells. The precise role of RME in vasopressin action is uncertain, but it is likely that it is involved in the desensitization of target cells by altering the number of cell surface vasopressin receptors. Alterations in the rate of RME may alter the response of the cell to vasopressin. Fluorescent and biotinylated vasopressins are useful tools for the study of this process.
Sandra L. Schmid - One of the best experts on this subject based on the ideXlab platform.
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A nostalgic look back 40 years after the discovery of Receptor-Mediated Endocytosis.
Molecular biology of the cell, 2019Co-Authors: Sandra L. SchmidAbstract:The concept of Receptor-Mediated Endocytosis was proposed 40 years ago in a seminal review by Joseph Goldstein, Michael Brown, and Richard Anderson. Not only their hypothesis but also the lessons learned that guided their discovery have stood the test of time. I recount some of these herein, while also looking back nostalgically at a forgotten era of scientific communication.
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Actin assembly plays a variable, but not obligatory role in Receptor-Mediated Endocytosis in mammalian cells.
Traffic (Copenhagen Denmark), 2000Co-Authors: L. Miya Fujimoto, John E. Heuser, Robyn Roth, Sandra L. SchmidAbstract:Three cell-permeant compounds, cytochalasin D, latrunculin A and jasplakinolide, which perturb intracellular actin dynamics by distinct mechanisms, were used to probe the role of filamentous actin and actin assembly in clathrin-mediated Endocytosis in mammalian cells. These compounds had variable effects on Receptor-Mediated Endocytosis of transferrin that depended on both the cell line and the experimental protocol employed. Endocytosis in A431 cells assayed in suspension was inhibited by latrunculin A and jaspiakinolide, but resistant to cytochalasin D, whereas neither compound inhibited Endocytosis in adherent A431 cells. In contrast, Endocytosis in adherent CHO cells was more sensitive to disruption of the actin cytoskeleton than Endocytosis in CHO cells grown or assayed in suspension. Endocytosis in other cell types, including nonadherent K562 human erythroleukemic cells or adherent Cos-7 cells was unaffected by disruption of the actin cytoskeleton. While it remains possible that actin filaments can play an accessory role in Receptor-Mediated Endocytosis, these discordant results indicate that actin assembly does not play an obligatory role in endocytic coated vesicle formation in cultured mammalian cells.
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impairment of dynamin s gap domain stimulates receptor mediated Endocytosis
Nature, 1999Co-Authors: Sanja Sever, Amy B Muhlberg, Sandra L. SchmidAbstract:Dynamin is a GTP-hydrolysing protein that is an essential participant in clathrin-mediated Endocytosis by cells. It self-assembles into ‘collars’ in vitro which also form in vivo at the necks of invaginated coated pits. This self-assembly stimulates dynamin's GTPase activity and it has been proposed that dynamin hydrolyses GTP in order to generate the force needed to sever vesicles from the plasma membrane. A mechanism is now described in which self-assembly of dynamin is coordinated by a domain of dynamin with a GTPase-activating function. Unexpectedly, when dynamin mutants defective in self-assembly-stimulated GTPase activity are overexpressed, Receptor-Mediated Endocytosis is accelerated. The results indicate that dynamin, like other members of the GTPase superfamily, functions as a molecular regulator in Receptor-Mediated Endocytosis, rather than as a force-generating GTPase.
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The Actin Cytoskeleton Is Required for Receptor-Mediated Endocytosis in Mammalian Cells
The Journal of biological chemistry, 1997Co-Authors: Christophe Lamaze, L. Miya Fujimoto, Helen L. Yin, Sandra L. SchmidAbstract:Actin filament organization is essential for Endocytosis in yeast. In contrast, the actin-depolymerizing agent cytochalasin D has yielded ambiguous results as to a role for actin in Receptor-Mediated Endocytosis in mammalian cells. We have therefore re-examined this issue using highly specific reagents known to sequester actin monomers. Two of these reagents, thymosin β4 and DNase I, potently inhibited the sequestration of transferrin receptors into coated pits as measured in a cell-free system using perforated A431 cells. At low concentrations, thymosin β4 but not DNase I was stimulatory. Importantly, the effects of both reagents were specifically neutralized by the addition of actin monomers. A role for the actin cytoskeleton was also detected in intact cells where latrunculin A, a drug that sequesters actin monomers, inhibited Receptor-Mediated Endocytosis. Biochemical and morphological analyses suggest that these reagents inhibit later events in coated vesicle budding. These results provide new evidence that the actin cytoskeleton is required for Receptor-Mediated Endocytosis in mammalian cells.
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Regulation of Receptor-Mediated Endocytosis by Rho and Rac
Nature, 1996Co-Authors: Christophe Lamaze, Tsung-hsein Chuang, Laura J. Terlecky, Gary M. Bokoch, Sandra L. SchmidAbstract:PINOCYTOSIS and membrane ruffling are among the earliest and most dramatic cellular responses to stimulation by growth factors or other mitogens1. The small Ras-related G proteins Rho and Rac have a regulatory role in membrane ruffling1–3 and activated Rho has been shown to stimulate pinocytosis when microinjected into Xenopus oocytes4. In contrast to these well established effects of Rho and Rac on plasma membrane morphology and bulk pinocytosis, there has been no evidence for their involvement in the regulation of Receptor-Mediated Endocytosis in clathrin-coated pits. Here we show that activated Rho and Rac inhibit transferrin-Receptor-Mediated Endocytosis when expressed in intact cells. Furthermore, we have reconstituted these effects in a cell-free system and established that Rho and Rac can regulate clathrin-coated vesicle formation.
Ward Lutz - One of the best experts on this subject based on the ideXlab platform.
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Vasopressin Receptor-Mediated Endocytosis in cells transfected with V1-type vasopressin receptors
Kidney International, 1993Co-Authors: Ward Lutz, Mark A. Sanders, Jeffrey L. Salisbury, Stephen Lolait, Anne Marie O'carroll, Rajiv KumarAbstract:Vasopressin Receptor-Mediated Endocytosis in cells transfected with V 1 -type vasopressin receptors. We examined the process of Receptor-Mediated Endocytosis in A-9 lung fibroblast and chinese hamster ovary (CHO) cells transfected with the recently cloned vasopressin V 1a receptor (51). We used a fluorescent labeled vasopressin analog (rho-damine-mercaptopropionic acid lysine vasopressin) and radiolabeled vasopressin to examine this process in the two transfected cell lines. Both A-9 and CHO cells internalize vasopressin in a manner consistent with Receptor-Mediated Endocytosis. A-9 cells internalize vasopressin more rapidly than CHO cells. The process is inhibited by vasopressin and by specific vasopressin V 1 receptor antagonists but not by specific V 2 receptor antagonists. Hypertonic sucrose inhibits Endocytosis in both cell types suggesting a role of clathrin coated pits in the Endocytosis of receptor in these cells. These cells are excellent models in which to examine the effect of receptor mutations on vasopressin Receptor-Mediated Endocytosis.
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Vasopressin Receptor-Mediated Endocytosis: current view
American Journal of Physiology-Renal Physiology, 1991Co-Authors: Ward Lutz, Jeffrey L. Salisbury, Rajiv KumarAbstract:A number of peptide hormones have been shown to undergo Receptor-Mediated Endocytosis (RME). RME involves the internalization of receptor-ligand complexes followed by delivery to an intracellular compartment, the endosome, from which ligands or receptors can be delivered to lysosomes or other cellular destinations. Vasopressin, a peptide hormone that plays a role in kidney and vascular physiology, has recently been demonstrated to undergo RME in LLC-PK1 and A10 cells, which express V2- and V1-type vasopressin receptors, respectively. Fluorescent vasopressin analogues are internalized by RME from the basolateral surface of polarized LLC-PK1 cells. The precise role of RME in vasopressin action is uncertain, but it is likely that it is involved in the desensitization of target cells by altering the number of cell surface vasopressin receptors. Alterations in the rate of RME may alter the response of the cell to vasopressin. Fluorescent and biotinylated vasopressins are useful tools for the study of this process.
Mikihisa Takano - One of the best experts on this subject based on the ideXlab platform.
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Cisplatin-induced inhibition of Receptor-Mediated Endocytosis of protein in the kidney
Kidney international, 2002Co-Authors: Mikihisa Takano, Naoki Nakanishi, Yasumi Kitahara, Yuki Sasaki, Teruo Murakami, Junya NagaiAbstract:Cisplatin-induced inhibition of Receptor-Mediated Endocytosis of protein in the kidney. Background Administration of cisplatin, cis-diamminedichloroplatinum (II) (CDDP), causes a severe impairment of renal function, including increases in urinary excretion of proteins. We recently found that CDDP inhibits vacuolar H + -ATPase, which plays an important role in Receptor-Mediated Endocytosis in the renal proximal tubules. Therefore, CDDP-induced proteinuria may be due to an inhibition of the Receptor-Mediated Endocytosis in the renal proximal tubules following a decrease in vacuolar H + -ATPase activity by the drug. Methods Effects of CDDP on Receptor-Mediated Endocytosis of albumin in opossum kidney (OK) epithelial cells, and on urinary excretion of albumin and vitamin D binding protein, which are reabsorbed in the renal proximal tubules by Endocytosis, in rats were examined. Results CDDP inhibited uptake of fluorescein-isothiocyanate (FITC)-albumin, a Receptor-Mediated Endocytosis marker, by OK cells in a time- and concentration-dependent fashion. In contrast, CDDP treatment did not affect the uptake of FITC-inulin, a fluid-phase Endocytosis marker. CDDP caused a decrease in the affinity and in the maximal velocity of FITC-albumin uptake. The adenosine 5′-triphosphate (ATP) content in OK cells was not changed by CDDP at concentrations that inhibited FITC-albumin uptake. The endosomal pH in OK cells was increased by CDDP treatment. Administration of CDDP to rats increased the urinary excretion of albumin and vitamin D binding protein. Conclusions These results suggest that CDDP decreases the Receptor-Mediated Endocytosis of protein following the inhibition of vacuolar H + -ATPase in the renal proximal tubules, and the inhibition of Receptor-Mediated Endocytosis would be the mechanisms underlying the proteinuria induced by CDDP.
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Expression of Chloride Channel, ClC-5, and Its Role in Receptor-Mediated Endocytosis of Albumin in OK Cells
Biochemical and biophysical research communications, 2001Co-Authors: Yuki Sasaki, Yasumi Kitahara, Teruo Murakami, Junya Nagai, Natsuko Takai, Mikihisa TakanoAbstract:Abstract By using Western blot and RT-PCR analyses, the expression of ClC-5, a member of the ClC family of voltage-gated chloride channels, and its mRNA was detected in OK cells. The effect of chloride channel inhibitors on Receptor-Mediated Endocytosis of albumin was examined in OK cells and compared to that of vacuolar H + -ATPase inhibitors. Accumulation of fluorescein-isothiocyanate (FITC)–albumin, a Receptor-Mediated Endocytosis marker, was inhibited by 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), a chloride channel inhibitor, in a concentration-dependent fashion. In contrast, uptake of FITC–inulin, a fluid-phase Endocytosis marker, was not affected by NPPB. Other chloride channel inhibitors, 4,4′-diisothiocyanatostilbene-2-2′-disulfonic acid and diphenylamine-2-carboxylic acid, also inhibited FITC–albumin uptake. NPPB, as well as a vacuolar H + -ATPase inhibitor bafilomycin A 1 , caused a decrease in the affinity and in the maximal velocity of FITC–albumin uptake. These results suggest that chloride channel, most likely ClC-5, plays an important role in the Receptor-Mediated Endocytosis of albumin in OK cells.
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Receptor-Mediated Endocytosis in Renal Tubules and its Dysfunction Induced by Drugs
Drug Metabolism and Pharmacokinetics, 2001Co-Authors: Mikihisa TakanoAbstract:In the kidney, various compounds in the plasma are filtrated through glomeruli. Though the glomerular filtration of many plasma proteins is restricted because of their large molecular weights, still significant amount of proteins is filtered. The proteins filtered are reabsorbed in the proximal tubular cells almost completely. The mechanism involved in protein reabsorption is Receptor-Mediated Endocytosis. Not only proteins but also drugs such as aminoglycoside antibiotics are taken up by Receptor-Mediated Endocytosis in renal proximal tubules. Megalin is a large (ca. 600 kDa) endocytic receptor, which is abundantly expressed in renal proximal tubules, and recognizes various compounds such as lipoprotein lipase, aprotinin, transcobalamin-vitamin B12, apolipoprotein J/clusterin, RAP (receptor-associated protein), 25-(OH) vitamin D3-vitamin D binding protein complex as substrates. Albumin, a major plasma protein, was initially reported as a substrate for megalin, but recently the involvement of another protein, cubilin, in albumin Endocytosis was indicated. Namely, albumin binds to cubilin, and albumin-cubilin complex binds to megalin for Endocytosis; the hypothesis which should be tested further. Megalin is also suggested to be the receptor for Endocytosis of aminoglycosides. We have studied the possible role of megalin in in vivo renal accumulation of aminoglycosides. The positive relationship between megalin expression and amikacin accumulation in renal cortex, either under normal or disease condition, strongly suggests that megalin acts as an endocytic receptor for aminoglycosides. There are two important functional proteins for endosomal acidification, which is important for overall endocytic process; these are vacuolar H+-ATPase (V-H+-ATPase) and chloride channel, ClC-5. Cisplatin, an anticancer drug, often induces nephrotoxicity, which is accompanied by albumin(protein) uria. In order to clarify the mechanisms underlying albuminuria by cisplatin, we examined the effect of cisplatin treatment on V-H+-ATPase activity in the kidney. Proton transporting activity as well as ATP hydrolysis activity of V-H+-ATPase was markedly inhibited by cisplatin treatment. Similarly, receptormediated Endocytosis of albumin was inhibited by cisplatin in OK cells and in vivo in rats. Reabsorption of a megalin substrate, vitamin D binding protein, was also inhibited and excreted into the urine. These findings suggest that albumin (protein) uria induced by cisplatin would be due to inhibition of V-H+-ATPase. Receptor-Mediated Endocytosis in the kidney is physiologically and pathophisiologically important process. Also, understanding the Receptor-Mediated Endocytosis would help to consider drug delivery systems, especially those for proteins and genes with large molecular weights.
Sang Chul Park - One of the best experts on this subject based on the ideXlab platform.
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Functional recovery of senescent cells through restoration of Receptor-Mediated Endocytosis.
Mechanisms of ageing and development, 2002Co-Authors: Sang Chul ParkAbstract:The functional deterioration of an organism with age causes the major problem of maintaining the quality of life at old age. Degenerative changes in the organism may to some extent reflect alterations that can be observed in cells during in vitro replicative senescence. At the cellular level, the Receptor-Mediated Endocytosis in the membrane might be emphasized as a responsible mechanism for functional decay, since the Endocytosis is in charge of many important biological phenomena: nutrient uptake, growth factor sensitivity, immune response, protection from environment and pathogen uptake, etc. We found that two major endocytotic pathways, i.e. clathrin-mediated and caveolae-dependent Endocytosis, are down regulated in senescent cells. For the down regulation of the clathrin dependent Receptor-Mediated Endocytosis, the reduction of amphiphysin-1 was found responsible, which was confirmed by Western blot analysis, dominant negative mutant transfection and restoration of gene activity by microinjection. With respect to the hypo-responsiveness of senescent cells to growth factors, the upregulation of caveolins has been suggested to be a causal factor. The overexpression of caveolins caused senescent-like changes in epidermal growth factor (EGF) response of the young cells, while down regulation of caveolins by use of antisense-oligonucleotides restored the EGF response in old cells, suggesting that caveolin system would be one of the major mechanisms responsible for decreased responses to growth factors in the senescent cells. Based on these results, it can be suggested that the functional deterioration of the senescent cells may be explained in terms of the down regulation of receptor mediated Endocytosis, at least in part, and that the restoration of Endocytosis apparatus either with amphiphysin supplementation or with reduction of caveolins might lead to functional recovery of the senescent cells.
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Down‐regulation of Receptor‐mediated Endocytosis Is Reponsible for Senescence‐associated Hyporesponsiveness
Annals of the New York Academy of Sciences, 2002Co-Authors: Sang Chul Park, Jeong-soo Park, Woong-yang Park, Kyoung-a Cho, Jeong Soo Ahn, Ik Soon JangAbstract:Human diploid fibroblasts (HDF) do not divide indefinitely and eventually lead to an arrest of cell division by a process termed cellular or replicative senescence. Irreversible growth arrest of senescent cells is strongly related to the attenuated response to growth factors. Recently, we reported that up-regulation of caveolin in the senescent cells is responsible for the attenuated response to growth factors. Senescent cells did not phosphorylate Erk-1/2 after EGF stimulation, whereas young cells did. In those senescent cells, we found an increased level of caveolin proteins and strong interactions between caveolin-1 and EGFR. When we overexpressed caveolin-1 in young HDF, the activation of Erk-1/2 on EGF stimulation was significantly suppressed. These results suggest that the hyporesponsiveness of senescent fibroblasts to EGF stimulation might be due to the overexpression of caveolin. In addition, the clathrin-dependent Endocytosis system plays the more active and dominant role over the caveolae system. Therefore, we monitored the efficiency of clathrin-dependent Receptor-Mediated Endocytosis in the senescent cells in order to elucidate the exact mode of the attenuated response to growth factors in the senescent cells. Using a transferrin-uptake assay and Western blot analysis of Endocytosis-related proteins, we found a significant decrease of amphiphysin-1 in human diploid fibroblasts of multipassages. By adjusting the level of amphiphysin, we could modulate the efficiency of Receptor-Mediated Endocytosis either in young or old cells toward growth factors: that is, a dominant negative mutant of amphiphysin-1 blocked the Endocytosis in the young cells, while microinjection of the gene resumed its activity in the old cells. Taken together, we conclude that the loss of endocytotic activity of senescent cells is directly related to the down-regulation of amphiphysin-1 and/or up-regulation of caveolins. This opens a new field of functional recovery of the senescent cells simply through adjusting the Receptor-Mediated Endocytosis capacity.
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Down-regulation of amphiphysin-1 is responsible for reduced Receptor-Mediated Endocytosis in the senescent cells.
FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 2001Co-Authors: Jeong-soo Park, Woong-yang Park, Kyoung-a Cho, Deok-in Kim, Byung-hak Jhun, Seung-ryul Kim, Sang Chul ParkAbstract:See CORRECTIONSPECIFIC AIMSHuman diploid fibroblasts undergo multiple functional alterations during their senescence process. Most of all, senescent cells do not respond properly to external stimuli and do not uptake materials as efficiently as presenescent cells. To elucidate the reason for such attenuated response of senescent cells, we attempted to monitor the functional capacity and molecular mechanism for the clathrin-dependent, Receptor-Mediated Endocytosis in the senescent cells, and tried to find principal molecules responsible for the decreased endocytotic activity in senescent cells that might be a target of intervention for the age-related dysfunctions.PRINCIPAL FINDINGS1. Clathrin-dependent Receptor-Mediated Endocytosis is blocked in senescent human diploid fibroblastsTo investigate the functional changes in the Receptor-Mediated Endocytosis during cellular senescence, we treated the early and late-passaged fibroblasts with tetramethylrhodamine-conjugated transferrin. Presenescent fibroblasts ...
