Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.6.3.44 (P-glycoprotein)
 13,344 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Lith1 region on Chromosome (Chr) 2 contains a gene that markedly affects the prevalence of cholesterol gallstones in inbred mice. We report the high-resolution genetic and radiation hybrid maps of the chromosomal region surrounding Lith1, using three resources: a DNA panel from 188 progeny from two reciprocal backcrosses between C57BL/6 and Mus spretus inbred strains; 423 progeny of an N4 generation from backcrossing the susceptible C57L/J alleles at Lith1 into the resistant AKR/J strain; and the newly developed hamster-mouse T31 radiation hybrid panel. We mapped 17 microsatellite markers in the D2Mit182 to D2Mit14 region and two candidate genes for Lith1, the canalicular bile salt export pump (Bsep) also known as sister of P-glycoprotein (Spgp) and the low-density-lipoprotein-receptor-related gene megalin (Gp330). Both genetic maps were in agreement and ordered the microsatellite markers into a 10.4 +/- 1.5 cM region. The high-resolution physical map revealed ordering of microsatellite markers and relative distances between markers in almost complete agreement with the genetic maps. Mapping of Bsep revealed its location on Chr 2, homologous to the human chromosomal position (Nature Genet 20, 233-238, 1998). The radiation hybrid results also provided the highest resolution of the area containing the two candidate genes, which both mapped in the Lith1 region with close linkage, being separated by a distance of only 15 cR(3000). The total radiation hybrid map length of the region between D2Mit182 and D2Mit14 was 326 cR(3000), suggesting that 31 cR(3000) is equivalent to 1 cM in this region of Chr 2.
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PMID:High-resolution maps of the murine Chromosome 2 region containing the cholesterol gallstone locus, Lith1. 1055 25

Cadmium (Cd(2+)) is a nonessential divalent metal ion that causes toxicity in multiple organs in humans. In order for toxicity to occur Cd(2+) must first enter cells by utilizing transport pathways for essential metals. This review focuses on studies in which Cd(2+) transport was directly demonstrated by electrophysiological, radiotracer or Cd(2+)-sensitive fluorescent dye techniques. The chemistry of Cd(2+) and metal ions in general is addressed in the context of properties relevant for transport through membrane proteins, such as hydration energy. Apart from transport by the ZIP transporters SLC39A8 and SLC39A14, which is not topic of the review, uptake of free Cd(2+) has been demonstrated for the Fe(2+)/H(+) cotransporter divalent metal transporter 1. Moreover, the multiligand endocytic receptors megalin and cubilin take up cadmium-metallothionein complexes via receptor-mediated endocytosis. The role of ATP binding cassette transporters in Cd(2+) efflux from cells is also discussed. Both the multidrug resistance-associated protein 1 and cystic fibrosis transmembrane conductance regulator are likely to transport cadmium-glutathione complexes out of cells, whereas transport of free Cd(2+) by the multidrug resistance P-glycoprotein remains controversial. Finally, arguments for and against Cd(2+) transport by Ca(2+) channels are presented. Most N- and L-type Ca(2+) channels are closed at resting membrane potential (with the exception of CaV1.3 channels) and therefore unlikely to allow significant Cd(2+) influx under physiological conditions. CaV3.1 and CaV3.2 T-type calcium channels are permeated by divalent metal ions, such as Fe(2+) and Mn(2+) because of considerable "window" currents close to resting membrane potential and could be responsible for tonic Cd(2+) entry. TRPM7 and the mitochondrial Ca(2+) uniporter are other likely candidates for Cd(2+) transporters, whereas the role of Orai proteins, the store-operated calcium channels carrying Ca(2+) release-activated Ca(2+) current, in Cd(2+) influx remains to be investigated.
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PMID:Catch me if you can! Novel aspects of cadmium transport in mammalian cells. 2020 75

Apical transport is key in renal function, and the activity of efflux transporters and receptor-mediated endocytosis is pivotal in this process. The conditionally immortalized proximal tubule epithelial cell line (ciPTEC) endogenously expresses these systems. Here, we used ciPTEC to investigate the activity of three major efflux transporters, viz., breast cancer resistance protein (BCRP), multidrug resistance protein 4 (MRP4), and P-glycoprotein (P-gp), as well as protein uptake through receptor-mediated endocytosis, using a fluorescence-based setup for transport assays. To this end, cells were exposed to Hoechst33342, chloromethylfluorescein-diacetate (CMFDA), and calcein-AM in the presence or absence of model inhibitors for BCRP (KO143), P-gp (PSC833), or MRPs (MK571). Overexpression cell lines MDCKII-BCRP and MDCKII-P-gp were used as positive controls, and membrane vesicles overexpressing one transporter were used to determine substrate and inhibitor specificities. Receptor-mediated endocytosis was investigated by determining the intracellular accumulation of fluorescently labeled receptor-associated protein (RAP-GST). In ciPTEC, BCRP and P-gp showed similar expressions and activities, whereas MRP4 was more abundantly expressed. Hoechst33342, GS-MF, and calcein are retained in the presence of KO143, MK571, and PSC833, showing clearly redundancy between the transporters. Noteworthy is the fact that both KO143 and MK571 can block BCRP, P-gp, and MRPs, whereas PSC833 appears to be a potent inhibitor for BCRP and P-gp but not the MRPs. Furthermore, ciPTEC accumulates RAP-GST in intracellular vesicles in a dose- and time-dependent manner, which was reduced in megalin-deficient cells. In conclusion, fluorescent-probe-based assays are fast and reproducible in determining apical transport mechanisms, in vitro. We demonstrate that typical substrates and inhibitors are not specific for the designated transporters, reflecting the complex interactions that can take place in vivo. The set of tools we describe are also compatible with innovative kidney culture models and allows studying transport mechanisms that are central to drug absorption, disposition, and detoxification.
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PMID:Fluorescence-Based Transport Assays Revisited in a Human Renal Proximal Tubule Cell Line. 2687 Dec 98

The main physiological functions of renal proximal tubule cells in vivo are reabsorption of essential nutrients from the glomerular filtrate and secretion of waste products and xenobiotics into urine. Currently, there are several established cell lines of human origin available as in vitro models of proximal tubule. However, these cells appeared to be limited in their biological relevance, because essential characteristics of the original tissue are lost once the cells are cultured. As a consequence of these limitations, primary human proximal tubule cells constitute a suitable and a biologically more relevant in vitro model to study this specific segment of the nephron and therefore, these cells can play an important role in renal regenerative medicine applications. Here, we describe a protocol to isolate proximal tubule cells from human nephrectomies. We explain the steps performed for an in-depth characterization of the cells, including the study of markers from others segments of the nephron, with the goal to determine the purity of the culture and the stability of proteins, enzymes, and transporters along time. The human proximal tubule cells isolated and used throughout this study showed many proximal tubule characteristics, including monolayer organization, cell polarization with the expression of tight junctions and primary cilia, expression of proximal tubule-specific proteins, such as megalin and sodium/glucose cotransporter 2, among others. The cells also expressed enzymatic activity for dipeptidyl peptidase IV, as well as for gamma glutamyl transferase 1, and expressed transporter activity for organic anion transporter 1, P-glycoprotein, multidrug resistance proteins, and breast cancer resistance protein. In conclusion, characterization of our cells confirmed presence of putative proximal tubule markers and the functional expression of multiple endogenous organic ion transporters mimicking renal reabsorption and excretion. These findings can constitute a valuable tool in the development of bioartificial kidney devices.
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PMID:A simple method for the isolation and detailed characterization of primary human proximal tubule cells for renal replacement therapy. 3138 50