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)

We compared the membrane proteins of autolysosomes isolated from leupeptin-administered rat liver with those of lysosomes. In addition to many polypeptides common to the two membranes, the autolysosomal membranes were found to be more enriched in endoplasmic reticulum lumenal proteins (protein-disulfide isomerase, calreticulin, ER60, BiP) and endosome/Golgi markers (cation-independent mannose 6-phosphate receptor, transferrin receptor, Golgi 58-kDa protein) than lysosomal membranes. The autolysosomal membrane proteins include three polypeptides (44, 35, and 32 kDa) whose amino-terminal sequences have not yet been reported. Combining immunoblotting and reverse transcriptase-polymerase chain reaction analyses, we identified the 44-kDa peptide as the intact subunit of betaine homocysteine methyltransferase and the 35- and 32-kDa peptides as two proteolytic fragments. Pronase digestion of autolysosomes revealed that the 44-kDa and 32-kDa peptides are present in the lumen, whereas the 35-kDa peptide is not. In primary hepatocyte cultures, the starvation-induced accumulation of the 32-kDa peptide occurs in the presence of E64d, showing that the 32-kDa peptide is formed from the sequestered 44-kDa peptide during autophagy. The accumulation is induced by rapamycin but completely inhibited by wortmannin, 3-methyladenine, and bafilomycin. Thus, detection of the 32-kDa peptide by immunoblotting can be used as a streamlined assay for monitoring autophagy.
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PMID:Autolysosomal membrane-associated betaine homocysteine methyltransferase. Limited degradation fragment of a sequestered cytosolic enzyme monitoring autophagy. 1032 31

Calnexin is a type I integral endoplasmic reticulum (ER) membrane chaperone involved in folding of newly synthesized (glycol)proteins. In this study, we used beta-galactosidase reporter gene knock-in and reverse transcriptase polymerase chain reaction (RT-PCR) to investigate activation of the calnexin gene during embryonic development. We showed that the calnexin gene was activated in neuronal tissue at the early stages of embryonic development but remained low in the heart, intestine, and smooth muscle. At early stages of embryonic development, large quantities of calnexin messenger RNA (mRNA) were also found in neuronal tissue and liver. There was no detectable calnexin mRNA in the heart, lung, and intestine. The absence of calnexin had no significant effect on ER stress response (unfolded protein response, UPR) at the tissue level as tested by IRE1-dependent splicing of Xbp1 mRNA. In contrast, non-stimulated calnexin-deficient cells showed increased activation of IRE1, as measured by RT-PCR and luciferase reporter gene analysis of splicing of Xbp1 mRNA and activation of the BiP promoter. This indicates that cnx (-/-) cells have increased constitutively active UPR. Importantly, cnx (-/-) cells have significantly increased proteasomal activity, which may play a role in the adaptive mechanisms addressing the acute ER stress observed in the absence of calnexin.
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PMID:Endoplasmic reticulum stress in the absence of calnexin. 1852 84