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)

Antibodies have been raised against synthetic peptides derived from the predicted primary sequence of the human cocaine- and antidepressant-sensitive norepinephrine (NE) transporter (NET). One antibody (N430), raised and purified against a putative intracellular human norepinephrine transporter (hNET) epitope, detects hNET expression in a stably transfected cell line (LLC-NET) by indirect immunofluorescence only in the presence of detergent, while no immunoreactivity is observed in either the parental cells (LLC-PK1) or in LLC-NET cells incubated with preimmune sera or peptide absorbed antibody. N430 immunoblots of LLC-NET cell extracts reveal two major immunoreactive hNET species in these cells, migrating at 80 and 54 kDa, respectively. Pulse-chase N430 immunoprecipitation studies confirm that the 54-kDa species is a transient, glycosylated intermediate of a longer lived, more highly glycosylated protein with an apparent M(r) of 80,000. In contrast, a 54-kDa species is the primary hNET product in vaccinia virus T7-infected HeLa cells, transiently transfected with hNET cDNA. PNGase F digestion of extracts prepared from LLC-NET- and hNET-transfected HeLa cells convert all immunoreactive species to a 46-kDa form, equivalent to that observed following incubation of whole cells with the glycosylation inhibitor tunicamycin. As transiently transfected HeLa and stable LLC-NET cells exhibit a pharmacologically similar NE transport activity, it appears likely that the additional glycosylation evident in the stable line does not contribute significantly to antagonist sensitivity. On the other hand, NE transport and antagonist ([125I]RTI-55) binding assays on whole LLC-NET cells treated with tunicamycin reveal a pronounced reduction in NE transport activity and hNET membrane density paralleled by an inability of NET proteins to replenish the higher M(r) hNET pool. These findings suggest an obligate role for N-linked glycosylation in hNET biosynthetic maturation, stability, and functional expression. In summary, N430 antibody is a useful tool for the visualization and characterization of hNET gene products and has permitted the first direct evaluation of biosynthetic steps leading to functional catecholamine transporter expression.
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PMID:Human norepinephrine transporter. Biosynthetic studies using a site-directed polyclonal antibody. 816 33

NaSi-1 encodes a Na(+)-sulfate cotransporter expressed on the apical membrane of renal proximal tubular cells, which is responsible for body sulfate homeostasis. Limited information is available on NaSi-1 protein structure and the mechanisms controlling its apical membrane sorting. The aims of this study were to biochemically determine the quaternary structure of the rat NaSi-1 protein and to characterize its expression in renal epithelial cell lines. Hexahistidyl-tagged NaSi-1 (NaSi-1-His) proteins expressed in Xenopus oocytes, appeared as two bands of about 60 and 75 kDa. PNGase F treatment shifted both bands to 57 kDa while endoglycosidase H treatment led to a downward shift of the lower molecular mass band only. Mutagenesis of a putative N-glycosylation site (N591S) produced a single band that was not shifted by endoglycosidase H or PNGase F, confirming a single glycosylation site at residue 591. Blue native-PAGE and cross-linking experiments revealed dimeric complexes, suggesting the native form of NaSi-1 to be a dimer. Transient transfection of EGFP/NaSi-1 in renal epithelial cells (OK, LLC-PK1 and MDCK) demonstrated apical membrane sorting, which was insensitive to tunicamycin. Transfection of the EGFP/NaSi-1 N591S glycosylation mutant also showed apical expression, suggesting N591 is not essential for apical sorting. Treatment with cholesterol depleting compounds did not disrupt apical sorting, but brefeldin A led to misrouting to the basolateral membrane, suggesting that NaSi-1 sorting is through the ER to Golgi pathway. Our data demonstrates that NaSi-1 forms a dimeric protein which is glycosylated at N591, whose sorting to the apical membrane in renal epithelial cells is brefeldin A-sensitive and independent of lipid rafts or glycosylation.
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PMID:Quaternary structure and apical membrane sorting of the mammalian NaSi-1 sulfate transporter in renal cell lines. 1768 82