Discovery of a Novel Target for the Dysglycemic Chromogranin A Fragment Pancreastatin: Interaction with the Chaperone GRP78 to Influence Metabolism

RATIONALE: The chromogranin A-derived peptide pancreastatin (PST) is a dysglycemic, counter-regulatory peptide for insulin action, especially in liver. Although previous evidence for a PST binding protein has been reported, such a receptor has not been identified or sequenced. METHODS AND RESULTS: W...

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Autores principales: Biswas, Nilima, Friese, Ryan S., Gayen, Jiaur R., Bandyopadhyay, Gautam, Mahata, Sushil K., O'Connor, Daniel T.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: Public Library of Science 2014
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3896336/
https://www.ncbi.nlm.nih.gov/pubmed/24465394
http://dx.doi.org/10.1371/journal.pone.0084132
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author Biswas, Nilima
Friese, Ryan S.
Gayen, Jiaur R.
Bandyopadhyay, Gautam
Mahata, Sushil K.
O'Connor, Daniel T.
author_facet Biswas, Nilima
Friese, Ryan S.
Gayen, Jiaur R.
Bandyopadhyay, Gautam
Mahata, Sushil K.
O'Connor, Daniel T.
author_sort Biswas, Nilima
collection PubMed
description RATIONALE: The chromogranin A-derived peptide pancreastatin (PST) is a dysglycemic, counter-regulatory peptide for insulin action, especially in liver. Although previous evidence for a PST binding protein has been reported, such a receptor has not been identified or sequenced. METHODS AND RESULTS: We used ligand affinity to purify the PST target, with biotinylated human PST (hCHGA(273–301)-amide) as “bait” and mouse liver homogenate as “prey”, and identified GRP78 (a.k.a. “78 kDa Glucose Regulated Protein”, HSPA5, BIP) as a major interacting partner of PST. GRP78 belongs to the family of heat shock proteins (chaperones), involved in several cellular processes including protein folding and glucose metabolism. We analyzed expression of GRP78 in the absence of PST in a mouse knockout model lacking its precursor CHGA: hepatic transcriptome data revealed global over-expression of not only GRP78 but also other heat shock transcripts (of the “adaptive UPR”) in CHGA(−/−) mice compared to wild-type (+/+). By contrast, we found a global decline in expression of hepatic pro-apoptotic transcripts in CHGA(−/−) mice. GRP78's ATPase enzymatic activity was dose-dependently inhibited by PST (IC(50)∼5.2 µM). PST also inhibited the up-regulation of GRP78 expression during UPR activation (by tunicamycin) in hepatocytes. PST inhibited insulin-stimulated glucose uptake in adipocytes, and increased hepatic expression of G6Pase (the final step in gluconeogenesis/glycogenolysis). In hepatocytes not only PST but also other GRP78-ATPase inhibitors (VER-155008 or ADP) increased G6Pase expression. GRP78 over-expression inhibited G6Pase expression in hepatocytes, with partial restoration by GRP78-ATPase inhibitors PST, VER-155008, or ADP. CONCLUSIONS: Our results indicate that an unexpected major hepatic target of PST is the adaptive UPR chaperone GRP78. PST not only binds to GRP78 (in pH-dependent fashion), but also inhibits GRP78's ATPase enzymatic activity, and impairs its biosynthetic response to UPR activation. PST decreases insulin-stimulated cellular glucose uptake, and PST as well as other chaperone ATPase activity inhibitors augment expression of G6Pase; GRP78 over-expression antagonizes this PST action. Analysis of the novel PST/GRP78 interaction may provide a new avenue of investigation into cellular glycemic control as well as dysglycemia.
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spelling pubmed-38963362014-01-24 Discovery of a Novel Target for the Dysglycemic Chromogranin A Fragment Pancreastatin: Interaction with the Chaperone GRP78 to Influence Metabolism Biswas, Nilima Friese, Ryan S. Gayen, Jiaur R. Bandyopadhyay, Gautam Mahata, Sushil K. O'Connor, Daniel T. PLoS One Research Article RATIONALE: The chromogranin A-derived peptide pancreastatin (PST) is a dysglycemic, counter-regulatory peptide for insulin action, especially in liver. Although previous evidence for a PST binding protein has been reported, such a receptor has not been identified or sequenced. METHODS AND RESULTS: We used ligand affinity to purify the PST target, with biotinylated human PST (hCHGA(273–301)-amide) as “bait” and mouse liver homogenate as “prey”, and identified GRP78 (a.k.a. “78 kDa Glucose Regulated Protein”, HSPA5, BIP) as a major interacting partner of PST. GRP78 belongs to the family of heat shock proteins (chaperones), involved in several cellular processes including protein folding and glucose metabolism. We analyzed expression of GRP78 in the absence of PST in a mouse knockout model lacking its precursor CHGA: hepatic transcriptome data revealed global over-expression of not only GRP78 but also other heat shock transcripts (of the “adaptive UPR”) in CHGA(−/−) mice compared to wild-type (+/+). By contrast, we found a global decline in expression of hepatic pro-apoptotic transcripts in CHGA(−/−) mice. GRP78's ATPase enzymatic activity was dose-dependently inhibited by PST (IC(50)∼5.2 µM). PST also inhibited the up-regulation of GRP78 expression during UPR activation (by tunicamycin) in hepatocytes. PST inhibited insulin-stimulated glucose uptake in adipocytes, and increased hepatic expression of G6Pase (the final step in gluconeogenesis/glycogenolysis). In hepatocytes not only PST but also other GRP78-ATPase inhibitors (VER-155008 or ADP) increased G6Pase expression. GRP78 over-expression inhibited G6Pase expression in hepatocytes, with partial restoration by GRP78-ATPase inhibitors PST, VER-155008, or ADP. CONCLUSIONS: Our results indicate that an unexpected major hepatic target of PST is the adaptive UPR chaperone GRP78. PST not only binds to GRP78 (in pH-dependent fashion), but also inhibits GRP78's ATPase enzymatic activity, and impairs its biosynthetic response to UPR activation. PST decreases insulin-stimulated cellular glucose uptake, and PST as well as other chaperone ATPase activity inhibitors augment expression of G6Pase; GRP78 over-expression antagonizes this PST action. Analysis of the novel PST/GRP78 interaction may provide a new avenue of investigation into cellular glycemic control as well as dysglycemia. Public Library of Science 2014-01-20 /pmc/articles/PMC3896336/ /pubmed/24465394 http://dx.doi.org/10.1371/journal.pone.0084132 Text en © 2014 Biswas et al http://creativecommons.org/licenses/by/4.0/ This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are properly credited.
spellingShingle Research Article
Biswas, Nilima
Friese, Ryan S.
Gayen, Jiaur R.
Bandyopadhyay, Gautam
Mahata, Sushil K.
O'Connor, Daniel T.
Discovery of a Novel Target for the Dysglycemic Chromogranin A Fragment Pancreastatin: Interaction with the Chaperone GRP78 to Influence Metabolism
title Discovery of a Novel Target for the Dysglycemic Chromogranin A Fragment Pancreastatin: Interaction with the Chaperone GRP78 to Influence Metabolism
title_full Discovery of a Novel Target for the Dysglycemic Chromogranin A Fragment Pancreastatin: Interaction with the Chaperone GRP78 to Influence Metabolism
title_fullStr Discovery of a Novel Target for the Dysglycemic Chromogranin A Fragment Pancreastatin: Interaction with the Chaperone GRP78 to Influence Metabolism
title_full_unstemmed Discovery of a Novel Target for the Dysglycemic Chromogranin A Fragment Pancreastatin: Interaction with the Chaperone GRP78 to Influence Metabolism
title_short Discovery of a Novel Target for the Dysglycemic Chromogranin A Fragment Pancreastatin: Interaction with the Chaperone GRP78 to Influence Metabolism
title_sort discovery of a novel target for the dysglycemic chromogranin a fragment pancreastatin: interaction with the chaperone grp78 to influence metabolism
topic Research Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3896336/
https://www.ncbi.nlm.nih.gov/pubmed/24465394
http://dx.doi.org/10.1371/journal.pone.0084132
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