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| Predicate | Object |
|---|---|
| rdf:type | |
| lifeskim:mentions | |
| pubmed:issue |
47
|
| pubmed:dateCreated |
1998-1-8
|
| pubmed:abstractText |
Variable amounts of soluble forms of a variety of glycosyl-phosphatidylinositol (GPI)-anchored proteins occur extracellularly, but the molecular mechanisms governing their release are not entirely clear. When the GPI-anchored folate receptor (FR) type beta was expressed transiently in human 293 fibroblasts, there was a roughly equal distribution of [3H]folic acid binding protein between the cell surface and the medium after 24 h over a wide range of expression levels of FR-beta. The difference in apparent molecular masses between the soluble FR-beta and the PI-PLC-treated membrane protein indicated that the former was not released from the membrane by the action of phospholipase. Brefeldin A inhibited the release of soluble FR-beta from both the transfected 293 cells and stable recombinant CHO (CHO-FR-beta) cells while pre-existing levels of cell surface FR were unaltered suggesting the absence of a precursor-product relationship between the membrane-associated FR-beta and the soluble protein in the medium. [35S]Cysteine pulse-chase analysis was consistent with this finding. Interchanging of carboxyl-terminal peptides between FR-beta and FR-alpha revealed that the nature of the processed signal for GPI modification was responsible for the quantitative membrane anchoring of FR-alpha and the production of soluble FR-beta. When total cell lysates were analyzed by Western blot, a diffuse band of apparent 41 kDa and three additional sharp bands of apparent 35, 33, and 29.3 kDa were seen. The 41 kDa band was identified as the PI-PLC sensitive cell surface receptor. Several mutant constructs of FR-beta, in which the carboxyl-terminal signal for GPI modification was either disrupted or deleted only gave the three lower bands. The three sharp bands from the wild-type and the mutant forms of FR-beta were identified as nonglycosylated (29.3 kDa) or glycosylated polypeptides in which the carboxyl-terminal peptide was at least partially proteolyzed without GPI modification. All of the mutations in the GPI signal resulted in the recovery of [3H]folic acid binding protein in the media which, similar to the wild-type FR recovered from the media, were converted to the 29.3 kDa band by N-glycanase. The results from this study indicate that a carboxyl-terminal peptide in FR-beta is efficiently proteolyzed intracellularly by a pathway that is independent of GPI signal recognition resulting in proper protein folding and secretion. Such carboxyl-terminal sequences could represent a simple adaptation for proteins whose physiologic functions reside both at the cell surface and in extracellular fluids, allowing their selective and tissue-specific release.
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| pubmed:grant | |
| pubmed:language |
eng
|
| pubmed:journal | |
| pubmed:citationSubset |
IM
|
| pubmed:chemical |
http://linkedlifedata.com/resource/pubmed/chemical/Carrier Proteins,
http://linkedlifedata.com/resource/pubmed/chemical/Folate Receptors, GPI-Anchored,
http://linkedlifedata.com/resource/pubmed/chemical/Folic Acid,
http://linkedlifedata.com/resource/pubmed/chemical/Glycosylphosphatidylinositols,
http://linkedlifedata.com/resource/pubmed/chemical/Oligodeoxyribonucleotides,
http://linkedlifedata.com/resource/pubmed/chemical/Phosphatidylinositol...,
http://linkedlifedata.com/resource/pubmed/chemical/Phosphoinositide Phospholipase C,
http://linkedlifedata.com/resource/pubmed/chemical/Receptors, Cell Surface,
http://linkedlifedata.com/resource/pubmed/chemical/Recombinant Fusion Proteins,
http://linkedlifedata.com/resource/pubmed/chemical/Recombinant Proteins,
http://linkedlifedata.com/resource/pubmed/chemical/Type C Phospholipases
|
| pubmed:status |
MEDLINE
|
| pubmed:month |
Nov
|
| pubmed:issn |
0006-2960
|
| pubmed:author | |
| pubmed:issnType |
Print
|
| pubmed:day |
25
|
| pubmed:volume |
36
|
| pubmed:owner |
NLM
|
| pubmed:authorsComplete |
Y
|
| pubmed:pagination |
14583-92
|
| pubmed:dateRevised |
2010-11-18
|
| pubmed:meshHeading |
pubmed-meshheading:9398177-Amino Acid Sequence,
pubmed-meshheading:9398177-Base Sequence,
pubmed-meshheading:9398177-Carrier Proteins,
pubmed-meshheading:9398177-Cell Line,
pubmed-meshheading:9398177-Cell Membrane,
pubmed-meshheading:9398177-Folate Receptors, GPI-Anchored,
pubmed-meshheading:9398177-Folic Acid,
pubmed-meshheading:9398177-Glycosylphosphatidylinositols,
pubmed-meshheading:9398177-Humans,
pubmed-meshheading:9398177-Molecular Sequence Data,
pubmed-meshheading:9398177-Mutagenesis, Site-Directed,
pubmed-meshheading:9398177-Oligodeoxyribonucleotides,
pubmed-meshheading:9398177-Phosphatidylinositol Diacylglycerol-Lyase,
pubmed-meshheading:9398177-Phosphoinositide Phospholipase C,
pubmed-meshheading:9398177-Receptors, Cell Surface,
pubmed-meshheading:9398177-Recombinant Fusion Proteins,
pubmed-meshheading:9398177-Recombinant Proteins,
pubmed-meshheading:9398177-Sequence Deletion,
pubmed-meshheading:9398177-Signal Transduction,
pubmed-meshheading:9398177-Transfection,
pubmed-meshheading:9398177-Type C Phospholipases
|
| pubmed:year |
1997
|
| pubmed:articleTitle |
Proteolysis of the carboxyl-terminal GPI signal independent of GPI modification as a mechanism for selective protein secretion.
|
| pubmed:affiliation |
Department of Biochemistry & Molecular Biology, Medical College of Ohio, Toledo 43699-0008, USA.
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| pubmed:publicationType |
Journal Article,
Research Support, U.S. Gov't, P.H.S.,
Research Support, Non-U.S. Gov't
|