Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P11021 (BiP)
 2,049 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Increased levels of the endoplasmic reticulum-resident protein folding chaperone BiP would be expected to either increase protein secretory capacity by improved solubilization of folding precursors or decrease secretory capacity by binding and retaining misfolded proteins. To address this question, the relationship between BiP levels and heterologous secretion in yeast was determined. A yeast strain was constructed in which BiP expression is tunable from 5 to 250% of wild-type levels, and this strain was used to explore the effect of varying BiP level on overall secretion of three heterologous proteins: human granulocyte colony-stimulating factor, Schizosaccharomyces pombe acid phosphatase, and bovine pancreatic trypsin inhibitor. For all three proteins examined, reduction in BiP expression below wild-type level diminished overall secretion, whereas 5-fold BiP overexpression from a constitutive glycolytic promoter did not substantially increase or decrease secretion titers. These results are consistent with a positive role for BiP in promoting membrane translocation and solubilization of folding precursors but are inconsistent with a negative role in proofreading and improper retention of heterologous secreted proteins.
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PMID:Reduction of BiP levels decreases heterologous protein secretion in Saccharomyces cerevisiae. 862 55

In this study, secretory processing of cell-surface displayed Aga2p fusions to bovine pancreatic trypsin inhibitor (BPTI) and the single chain Fv (scFv) antibody fragment D1.3 are examined. BPTI is more efficiently processed than D1.3 both when secreted and surface-displayed, and D1.3 expression imparts a greater amount of secretory stress on the cell as assayed by a reporter of the unfolded protein response (UPR). Surprisingly, simultaneous expression of the two proteins in the same cell somewhat improves BPTI surface display while decreasing D1.3 surface display with minimal effect on UPR activation. Furthermore, co-expression leads to the accumulation of punctate vacuolar aggregates of D1.3 and increased secretion of the D1.3-Aga2p fusion into the supernatant. Overexpression of the folding chaperones protein disulfide isomerase (PDI) and BiP largely mitigates the D1.3 surface expression decrease, suggesting that changes in vacuolar and cell surface targeting may be due, in part, to folding inefficiency. Titration of constitutive UPR expression across a broad range progressively decreases surface display of both proteins as UPR increases. D1.3-Aga2p traffic through the late secretory pathway appears to be strongly affected by overall secretory load as well as folding conditions in the ER.
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PMID:Contrasting secretory processing of simultaneously expressed heterologous proteins in Saccharomyces cerevisiae. 1633 64

Glycoprotein folding is mediated by lectin-like chaperones and protein disulfide isomerases (PDIs) in the endoplasmic reticulum. Calnexin and the PDI homologue ERp57 work together to help fold nascent polypeptides with glycans located toward the N-terminus of a protein, whereas PDI and BiP may engage proteins that lack glycans or have sugars toward the C-terminus. In this study, we show that the PDI homologue PDILT is expressed exclusively in postmeiotic male germ cells, in contrast to the ubiquitous expression of many other PDI family members in the testis. PDILT is induced during puberty and represents the first example of a PDI family member under developmental control. We find that PDILT is not active as an oxido-reductase, but interacts with the model peptide Delta-somatostatin and nonnative bovine pancreatic trypsin inhibitor in vitro, indicative of chaperone activity. In vivo, PDILT forms a tissue-specific chaperone complex with the calnexin homologue calmegin. The identification of a redox-inactive chaperone partnership defines a new system of testis-specific protein folding with implications for male fertility.
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PMID:A developmentally regulated chaperone complex for the endoplasmic reticulum of male haploid germ cells. 1750 49