Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.5.1.52 (PNGase F)
 1,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have analysed the contribution of several parameters, e.g. drug accumulation, MDR1 P-glycoprotein (P-gp), multidrug resistance-associated protein (MRP) and topoisomerase (topo) II, to drug resistance in a large set of drug-resistant variants of the human non-small-cell lung cancer cell line SW-1573 derived by selection with low concentrations of doxorubicin or vincristine. Selection with either drug nearly always resulted in MDR clones. The resistance of these clones could be explained by reduced drug accumulation and was associated with a decrease rather than an increase in the low MDR1 mRNA level. To test whether a decrease in MDR1 mRNA indirectly affected resistance in these cells, we introduced a MDR1-specific hammerhead ribozyme into wild-type SW-1573 cells. Although this led to a substantial reduction in MDR1 mRNA, it did not result in resistance. In all resistant clones we found an altered form of the multidrug resistance-associated protein (MRP), migrating slightly slower during SDS-polyacrylamide gel electrophoresis than MRP in parental cells. This altered MRP was also present in non-P-gp MDR somatic cell hybrids of the SW-1573 cells, demonstrating a clear linkage with the MDR phenotype. Treatment of crude cellular membrane fractions with N-glycanase, endoglycosidase H or neuraminidase showed that the altered migration of MRP on SDS-PAGE is due to a post-translational modification. There was no detectable difference in sialic acid content. In most but not all doxorubicin-selected clones, this MDR phenotype was accompanied by a reduction in topo II alpha mRNA level. No reduction was found in the clones selected with vincristine. We conclude from these results that selection of the SW-1573 cell line for low levels of doxorubicin or vincristine resistance, predominantly results in MDR with reduced drug accumulation associated with the presence of an altered MRP protein. This mechanism can be accompanied by other resistance mechanisms, such as reduced topo II alpha mRNA in case of doxorubicin selection.
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PMID:Altered MRP is associated with multidrug resistance and reduced drug accumulation in human SW-1573 cells. 764 Feb 9

The uterine sarcoma human cell line MES-SA/Dx5 overexpresses the MDR1 gene product, P-glycoprotein (Pgp). Pgp is a heavily glycosylated, ATP-dependent drug efflux pump expressed in many human cancers. There are more than 150 known isoforms of Pgp, which complicates the characterization of Pgp glycans because each isoform could present a different glycome. The contribution of these oligosaccharides to the structure and function of Pgp remains unclear. We identified distinct Pgp glycans recognized by the lectins in the digoxigenin (DIG) glycan differentiation kit from Roche Allied Science, all of which were N-glycans. Pgp was isolated using both slab and preparative gel elution. The monoclonal antibody C219 was used to identify the presence of Pgp and Pgp treated with PNGase F on our blots. Pgp isolated from MES-SA/Dx5 cells contains at least two different complex N-glycans--one high mannose tree, detected by GNA, and one branched hybrid oligosaccharide-capped with terminal sialic acids, detected by SNA and MAA. DSA, specific for biantennary oligosaccharides possessing beta(1-4)-N-acetyl-D-glucosamine residues, also recognized the blotted Pgp and is probably detecting the core Galbeta(1-4)-GlcNAc(x) component found in other Pgps.
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PMID:Distinct N-glycan glycosylation of P-glycoprotein isolated from the human uterine sarcoma cell line MES-SA/Dx5. 1769 67