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Allu PKR, Kiranmayi M, Mukherjee SD, Chirasani VR, Garg R, Vishnuprabu D, Ravi S, Subramanian L, Sahu BS, Iyer DR, Maghajothi S, Sharma S, Ravi MS, Khullar M, Munirajan AK, Gayen JR, Senapati S, Mullasari AS, Mohan V, Radha V, Naga Prasad SV, Mahapatra NR. Functional Gly297Ser Variant of the Physiological Dysglycemic Peptide Pancreastatin Is a Novel Risk Factor for Cardiometabolic Disorders. Diabetes 2022; 71:538-553. [PMID: 34862200 DOI: 10.2337/db21-0289] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/10/2021] [Accepted: 11/24/2021] [Indexed: 11/13/2022]
Abstract
Pancreastatin (PST), a chromogranin A-derived potent physiological dysglycemic peptide, regulates glucose/insulin homeostasis. We have identified a nonsynonymous functional PST variant (p.Gly297Ser; rs9658664) that occurs in a large section of human populations. Association analysis of this single nucleotide polymorphism with cardiovascular/metabolic disease states in Indian populations (n = 4,300 subjects) displays elevated plasma glucose, glycosylated hemoglobin, diastolic blood pressure, and catecholamines in Gly/Ser subjects as compared with wild-type individuals (Gly/Gly). Consistently, the 297Ser allele confers an increased risk (∼1.3-1.6-fold) for type 2 diabetes/hypertension/coronary artery disease/metabolic syndrome. In corroboration, the variant peptide (PST-297S) displays gain-of-potency in several cellular events relevant for cardiometabolic disorders (e.g., increased expression of gluconeogenic genes, increased catecholamine secretion, and greater inhibition of insulin-stimulated glucose uptake) than the wild-type peptide. Computational docking analysis and molecular dynamics simulations show higher affinity binding of PST-297S peptide with glucose-regulated protein 78 (GRP78) and insulin receptor than the wild-type peptide, providing a mechanistic basis for the enhanced activity of the variant peptide. In vitro binding assays validate these in silico predictions of PST peptides binding to GRP78 and insulin receptor. In conclusion, the PST 297Ser allele influences cardiovascular/metabolic phenotypes and emerges as a novel risk factor for type 2 diabetes/hypertension/coronary artery disease in human populations.
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Affiliation(s)
- Prasanna K R Allu
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, India
| | - Malapaka Kiranmayi
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, India
| | - Sromona D Mukherjee
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH
| | - Venkat R Chirasani
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, India
| | - Richa Garg
- Pharmaceutics & Pharmacokinetics Division, CSIR-Central Drug Research Institute, Lucknow, India
| | - Durairajpandian Vishnuprabu
- Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Chennai, India
| | - Sudesh Ravi
- Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Chennai, India
| | - Lakshmi Subramanian
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, India
| | - Bhavani S Sahu
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, India
| | - Dhanya R Iyer
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, India
| | - Sakthisree Maghajothi
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, India
| | - Saurabh Sharma
- Department of Experimental Medicine and Biotechnology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Marimuthu S Ravi
- Department of Cardiology, Madras Medical College and Government General Hospital, Chennai, India
| | - Madhu Khullar
- Department of Experimental Medicine and Biotechnology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Arasambattu K Munirajan
- Department of Genetics, Dr. ALM Post Graduate Institute of Basic Medical Sciences, University of Madras, Chennai, India
| | - Jiaur R Gayen
- Pharmaceutics & Pharmacokinetics Division, CSIR-Central Drug Research Institute, Lucknow, India
| | - Sanjib Senapati
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, India
| | - Ajit S Mullasari
- Institute of Cardiovascular Diseases, Madras Medical Mission, Chennai, India
| | - Viswanathan Mohan
- Department of Molecular Genetics, Madras Diabetes Research Foundation, Chennai, India
| | - Venkatesan Radha
- Department of Molecular Genetics, Madras Diabetes Research Foundation, Chennai, India
| | - Sathyamangala V Naga Prasad
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic, Cleveland, OH
| | - Nitish R Mahapatra
- Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology Madras, Chennai, India
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Discovery of a novel target for the dysglycemic chromogranin A fragment pancreastatin: interaction with the chaperone GRP78 to influence metabolism. PLoS One 2014; 9:e84132. [PMID: 24465394 PMCID: PMC3896336 DOI: 10.1371/journal.pone.0084132] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2013] [Accepted: 11/12/2013] [Indexed: 11/19/2022] Open
Abstract
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 (hCHGA273-301-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 (IC50∼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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Valicherla GR, Hossain Z, Mahata SK, Gayen JR. Pancreastatin is an endogenous peptide that regulates glucose homeostasis. Physiol Genomics 2013; 45:1060-71. [PMID: 24064537 DOI: 10.1152/physiolgenomics.00131.2013] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Pancreastatin (PST) is a regulatory peptide containing 49 amino acids, first isolated from porcine pancreas. Intracellular and extracellular processing of the prohormone Chromogranin A (Chga) results various bioactive peptides of which PST has dysglycemic activity. PST regulates glucose, lipid, and protein metabolism in liver and adipose tissues. It also regulates the secretion of leptin and expression of leptin and uncoupling protein 2 in adipose tissue. In Chga knockout mice, PST induces gluconeogenesis in the liver. PST reduces glucose uptake in mice hepatocytes and adipocytes. In rat hepatocytes, PST induces glycogenolysis and glycolysis and inhibits glycogen synthesis. In rat adipocytes, PST inhibits lactate production and lipogenesis. These metabolic effects are confirmed in humans. In the dual signaling mechanism of PST receptor, mostly PST activates Gαq/11 protein leads to the activation of phospholipase C β3-isoform, therefore increasing cytoplasmic free calcium and stimulating protein kinase C. PST inhibits the cell growth in rat HTC hepatoma cells, mediated by nitric oxide and cyclic GMP production. Elevated levels of PST correlating with catecholamines have been found in gestational diabetes and essential hypertension. Rise in the blood PST level in Type 2 diabetes suggests that PST is a negative regulator of insulin sensitivity and glucose homeostasis.
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Affiliation(s)
- Guru Raghavendra Valicherla
- Pharmacokinetics and Metabolism Division, Council of Scientific and Industrial Research-Central Drug Research Institute, Lucknow, India
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Sánchez-Margalet V, González-Yanes C, Najib S, Santos-Álvarez J. Reprint of: Metabolic effects and mechanism of action of the chromogranin A-derived peptide pancreastatin. ACTA ACUST UNITED AC 2010; 165:71-7. [PMID: 20934461 DOI: 10.1016/j.regpep.2010.10.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2009] [Revised: 02/09/2010] [Accepted: 02/11/2010] [Indexed: 01/12/2023]
Abstract
Pancreastatin is one of the regulatory peptides derived from intracellular and/or extracellular processing of chromogranin A, the soluble acidic protein present in the secretory granules of the neuroendocrine system. While the intracellular functions of chromogranin A include formation and maturation of the secretory granule, the major extracellular functions are generation of biologically active peptides with demonstrated autocrine, paracrine or endocrine activities. In this review, we will focus on the metabolic function of one of these peptides, pancreastatin, and the mechanisms underlying its effects. Many different reported effects have implicated PST in the modulation of energy metabolism, with a general counterregulatory effect to that of insulin. Pancreastatin induces glycogenolysis in liver and lipolysis in adipocytes. Metabolic effects have been confirmed in humans. Moreover, naturally occurring human variants have been found, one of which (Gly297Ser) occurs in the functionally important carboxy-terminus of the peptide, and substantially increases the peptide's potency to inhibit cellular glucose uptake. Thus, qualitative hereditary alterations in pancreastatin's primary structure may give rise to interindividual differences in glucose and lipid metabolism. Pancreastatin activates a receptor signaling system that belongs to the seven-spanning transmembrane receptor coupled to a Gq-PLCβ-calcium-PKC signaling pathway. Increased pancreastatin plasma levels, correlating with catecholamines levels, have been found in insulin resistance states, such as gestational diabetes or essential hypertension. Pancreastatin plays important physiological role in potentiating the metabolic effects of catecholamines, and may also play a pathophysiological role in insulin resistance states with increased sympathetic activity.
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Affiliation(s)
- Víctor Sánchez-Margalet
- Department of Medical Biochemistry and Molecular Biology, School of Medicine, Virgen Macarena University Hospital, University of Seville, Spain.
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Sánchez-Margalet V, González-Yanes C, Najib S, Santos-Alvarez J. Metabolic effects and mechanism of action of the chromogranin A-derived peptide pancreastatin. ACTA ACUST UNITED AC 2010; 161:8-14. [PMID: 20184923 DOI: 10.1016/j.regpep.2010.02.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2009] [Revised: 02/09/2010] [Accepted: 02/11/2010] [Indexed: 12/20/2022]
Abstract
Pancreastatin is one of the regulatory peptides derived from intracellular and/or extracellular processing of chromogranin A, the soluble acidic protein present in the secretory granules of the neuroendocrine system. While the intracellular functions of chromogranin A include formation and maturation of the secretory granule, the major extracellular functions are generation of biologically active peptides with demonstrated autocrine, paracrine or endocrine activities. In this review, we will focus on the metabolic function of one of these peptides, pancreastatin, and the mechanisms underlying its effects. Many different reported effects have implicated PST in the modulation of energy metabolism, with a general counterregulatory effect to that of insulin. Pancreastatin induces glycogenolysis in liver and lipolysis in adipocytes. Metabolic effects have been confirmed in humans. Moreover, naturally occurring human variants have been found, one of which (Gly297Ser) occurs in the functionally important carboxy-terminus of the peptide, and substantially increases the peptide's potency to inhibit cellular glucose uptake. Thus, qualitative hereditary alterations in pancreastatin's primary structure may give rise to interindividual differences in glucose and lipid metabolism. Pancreastatin activates a receptor signaling system that belongs to the seven-spanning transmembrane receptor coupled to a Gq-PLCbeta-calcium-PKC signaling pathway. Increased pancreastatin plasma levels, correlating with catecholamines levels, have been found in insulin resistance states, such as gestational diabetes or essential hypertension. Pancreastatin plays important physiological role in potentiating the metabolic effects of catecholamines, and may also play a pathophysiological role in insulin resistance states with increased sympathetic activity.
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Affiliation(s)
- Víctor Sánchez-Margalet
- Department of Medical Biochemistry and Molecular Biology, School of Medicine, Virgen Macarena University Hospital, University of Seville, Spain.
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Gayen JR, Saberi M, Schenk S, Biswas N, Vaingankar SM, Cheung WW, Najjar SM, O'Connor DT, Bandyopadhyay G, Mahata SK. A novel pathway of insulin sensitivity in chromogranin A null mice: a crucial role for pancreastatin in glucose homeostasis. J Biol Chem 2009; 284:28498-509. [PMID: 19706599 PMCID: PMC2781393 DOI: 10.1074/jbc.m109.020636] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2009] [Revised: 07/23/2009] [Indexed: 11/06/2022] Open
Abstract
Chromogranin A (CHGA/Chga), a proprotein, widely distributed in endocrine and neuroendocrine tissues (not expressed in muscle, liver, and adipose tissues), generates at least four bioactive peptides. One of those peptides, pancreastatin (PST), has been reported to interfere with insulin action. We generated a Chga knock-out (KO) mouse by the targeted deletion of the Chga gene in neuroendocrine tissues. KO mice displayed hypertension, higher plasma catecholamine, and adipokine levels and lower IL-6 and lipid levels compared with wild type mice. Liver glycogen content was elevated, but the nitric oxide (NO) level was diminished. Glucose, insulin, and pyruvate tolerance tests and hyperinsulinemic-euglycemic clamp studies established increased insulin sensitivity in liver but decreased glucose disposal in muscle. Despite higher catecholamine and ketone body levels and muscle insulin resistance, KO mice maintained euglycemia due to increased liver insulin sensitivity. Suppressed mRNA abundance of phosphoenolpyruvate carboxykinase and glucose-6-phosphatase (G6Pase) in KO mice further support this conclusion. PST administration in KO mice stimulated phosphoenolpyruvate carboxykinase and G6Pase mRNA abundance and raised the blood glucose level. In liver cells transfected with G6Pase promoter, PST caused transcriptional activation in a protein kinase C (PKC)- and NO synthase-dependent manner. Thus, PST action may be mediated by suppressing IRS1/2-phosphatidylinositol 3-kinase-Akt-FOXO-1 signaling and insulin-induced maturation of SREBP1c by PKC and a high level of NO. The combined effects of conventional PKC and endothelial NO synthase activation by PST can suppress insulin signaling. The rise in blood PST level with age and in diabetes suggests that PST is a negative regulator of insulin sensitivity and glucose homeostasis.
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Affiliation(s)
| | | | | | | | | | | | - Sonia M. Najjar
- the Center for Diabetes and Endocrine Research and Department of Physiology and Pharmacology, University of Toledo College of Medicine, Toledo, Ohio 43614-5804
| | - Daniel T. O'Connor
- From the Departments of Medicine
- Molecular Genetics, University of California, San Diego and
- Veterans Affairs San Diego Healthcare System, La Jolla, California 92093-0838 and
| | | | - Sushil K. Mahata
- From the Departments of Medicine
- Veterans Affairs San Diego Healthcare System, La Jolla, California 92093-0838 and
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Díaz-Troya S, Najib S, Sánchez-Margalet V. eNOS, nNOS, cGMP and protein kinase G mediate the inhibitory effect of pancreastatin, a chromogranin A-derived peptide, on growth and proliferation of hepatoma cells. ACTA ACUST UNITED AC 2005; 125:41-6. [PMID: 15582712 DOI: 10.1016/j.regpep.2004.07.031] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2004] [Revised: 06/21/2004] [Accepted: 07/23/2004] [Indexed: 10/26/2022]
Abstract
Pancreastatin (PST), a chromogranin A-derived peptide, has an anti-insulin metabolic effect and inhibits growth and proliferation by producing nitric oxide (NO) in HTC rat hepatoma cells. When NO production is blocked, a proliferative effect prevails due to the activation a Galphaq/11-phospholipase C-beta (PLC-beta) pathway, which leads to an increase in [Ca2+]i, protein kinase C (PKC) and mitogen-activated protein kinase (MAPK) activation. The aim of the present study was to investigate the NO synthase (NOS) isoform that mediates these effects of PST on HTC hepatoma cells and the possible roles of cyclic GMP (cGMP) and cGMP-dependent protein kinase. DNA and protein synthesis in response to PST were measured as [3H]-thymidine and [3H]-leucine incorporation in the presence of various pharmacological inhibitors: N-monomethyl-L-arginine (NMLA, nonspecific NOS inhibitor), L-NIO (endothelial nitric oxide synthase (eNOS) inhibitor), espermidine (neuronal nitric oxide synthase (nNOS) inhibitor), LY83583 (guanylyl cyclase inhibitor), and KT5823 (protein kinase G inhibitor, (PKG)). L-NIO, similarly to NMLA, reverted the inhibitory effect of PST on hepatoma cell into a stimulatory effect on growth and proliferation. Nevertheless, espermidine also prevented the inhibitory effect of PST, but there was no stimulation of growth and proliferation. When guanylyl cyclase activity was blocked, there was again a reversion of the inhibitory effect into a stimulatory action, suggesting that the effect of NO was mediated by the production of cGMP. PKG inhibition prevented the inhibitory effect of PST, but there was no stimulatory effect. Therefore, the inhibitory effect of PST on growth and proliferation of hepatoma cells may be mainly mediated by eNOS activation. In turn, the effect of NO may be mediated by cGMP, whereas other pathways in addition to PKG activation seem to mediate the inhibition of DNA and protein synthesis by PST in HTC hepatoma cells.
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Affiliation(s)
- Sandra Díaz-Troya
- Department of Medical Biochemistry and Molecular Biology, School of Medicine, Investigation Unit, University Hospital Virgen Macarena, Av. Sanchez Pizjuan 4, Seville 41009, Spain
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Sánchez-Margalet V, González-Yanes C, Najib S. Pancreastatin, a chromogranin A-derived peptide, inhibits DNA and protein synthesis by producing nitric oxide in HTC rat hepatoma cells. J Hepatol 2001; 35:80-5. [PMID: 11495046 DOI: 10.1016/s0168-8278(01)00071-x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
BACKGROUND/AIMS Pancreastatin, a chromogranin A-derived peptide, has a counter-regulatory effect on insulin action. We have previously characterized pancreastatin receptor and signalling in rat liver and HTC hepatoma cells. A G alpha(q/11)-PLC-beta pathway leads to an increase in [Ca2+]i, PKC and mitogen activated protein kinase (MAPK) activation. These data suggested that pancreastatin might have a role in growth and proliferation, similar to other calcium-mobilizing hormones. METHODS DNA and protein synthesis were measured as [3H]-thymidine and [3H]-leucine incorporation. Nitric oxide (NO) was determined by the Griess method and cGMP production was quantified by enzyme-linked immunoassay. RESULTS Contrary to the expected results, we have found that pancreastatin inhibits protein and DNA synthesis in HTC hepatoma cells. On the other hand, when the activity of NO synthase was inhibited by N-monomethyl-L-arginine (NMLA), the inhibitory effect of pancreastatin on DNA and protein synthesis was not only reverted, but a dose-dependent stimulatory effect was observed, probably due to MAPK activation, since it was prevented by PD98059. These data strongly suggested the role of NO in the inhibitory effect of pancreastatin on protein and DNA synthesis, which is overcoming the effect on MAPK activation. Moreover, pancreastatin dose-dependently increased NO production in parallel to cyclic guanosine monophosphate (cGMP). Both effects were prevented by NMLA. Finally, an indirect effect of pancreastatin through the induction of apoptosis was ruled out. CONCLUSIONS Therefore, the NO and the cGMP produced by the NO-activated guanylate cyclase may mediate the dose-dependent inhibitory effect of pancreastatin on growth and proliferation in HTC hepatoma cells.
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Affiliation(s)
- V Sánchez-Margalet
- Department of Medical Biochemistry and Molecular Biology, School of Medicine, University Hospital Virgen Macarena, Seville, Spain.
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Sánchez-Margalet V, González-Yanes C, Santos-Alvarez J, Najib S. Pancreastatin. Biological effects and mechanisms of action. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2001; 482:247-62. [PMID: 11192586 DOI: 10.1007/0-306-46837-9_20] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
Affiliation(s)
- V Sánchez-Margalet
- Department of Medical Biochemistry and Molecular Biology, School of Medicine, and Investigation Unit, University Hospital Virgen Macarena, Seville, Spain
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González-Yanes C, Santos-Alvarez J, Sánchez-Margalet V. Pancreastatin, a chromogranin A-derived peptide, activates Galpha(16) and phospholipase C-beta(2) by interacting with specific receptors in rat heart membranes. Cell Signal 2001; 13:43-9. [PMID: 11257446 DOI: 10.1016/s0898-6568(00)00127-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Pancreastatin (PST) is one of the chromogranin A (CGA)-derived peptides with known biological activity. It has a general inhibitory effect on secretion in many exocrine and endocrine systems including the heart atrium. Besides, a role of PST as a counter-regulatory peptide of insulin action has been proposed in the light of its effects on glucose and lipid metabolism in the liver and adipose tissue, where receptors and signaling have been described. Galpha(q/11) pathway seems to mediate PST action. Since PST has been shown to function as a typical calcium-dependent hormone, and increased plasma levels have been found in essential hypertension correlating with catecholamines, we sought to study its possible interaction and signaling in heart membranes. Here, we are characterizing specific PST binding sites and signaling in rat heart membranes. We have found that PST receptor has a K(d) of 0.5 nM and a B(max) of 34 fmol/mg of protein. The PST binding is inhibited by guanine nucleotides, suggesting the functional coupling of the receptor with GTP binding proteins (G proteins). Moreover, PST dose-dependently increases GTP binding to rat heart membranes. Finally, we have studied PST signaling-effector system by measuring phospholipase C (PLC) activity using blocking antibodies against different G proteins and PLC isoforms. We have found that PST stimulates PLCbeta(2)>PLCbeta(1)>PLCbeta(3) by activating Galpha(16) in rat heart membranes. These data suggest that PST may modulate the cardiac function.
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Affiliation(s)
- C González-Yanes
- Department of Medical Biochemistry and Molecular Biology, School of Medicine, University Hospital Virgen Macarena, Av. Sanchez Pizjuan 4, 41009, Seville, Spain
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Sánchez-Margalet V, González-Yanes C, Santos-Alvarez J, Najib S. Characterization of pancreastatin receptor and signaling in rat HTC hepatoma cells. Eur J Pharmacol 2000; 397:229-35. [PMID: 10844119 DOI: 10.1016/s0014-2999(00)00253-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Pancreastatin, a chromogranin A-derived peptide widely distributed throughout the neuroendocrine system, has a general inhibitory effect on endocrine secretion and a counterregulatory effect on insulin action. We have recently described the cross-talk of pancreastatin with insulin signaling in rat hepatoma cells (HTC), where it inhibits insulin action and signaling through the serine phosphorylation of the insulin receptor, thereby impairing tyrosine kinase activity. Here, we have characterized pancreastatin receptors and signaling in HTC cells. The pancreastatin effector systems were studied by determining phospholipase C activity in HTC membranes and mitogen-activated protein kinase (MAPK) phosphorylation activity in HTC cells. Binding studies with radiolabeled pancreastatin showed a population of high affinity binding sites, with a B(max) of 8 fmol/mg protein and a K(d) of 0.6 nM. Moreover, we assessed the coupling of the receptor with a G protein system by inhibiting the binding with guanine nucleotide and by measuring the GTP binding to HTC membranes. We found that pancreastatin receptor was coupled with a G alpha(q/11) protein which activates phospholipase C-beta(1) and phospholipase C-beta(3), in addition to MAPK via both beta gamma and alpha(q/11).
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Affiliation(s)
- V Sánchez-Margalet
- Departamento de Bioquímica Médica y Biología Molecular, Facultad de Medicina, Unidad de Investigación, Hospital Universitario Virgen Macarena, Universidad de Sevilla, Av. Sánchez Pizjuan 4, 41009, Sevilla, Spain.
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12
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Santos-Alvarez J, Sánchez-Margalet V. Affinity purification of pancreastatin receptor-Gq/11 protein complex from rat liver membranes. Arch Biochem Biophys 2000; 378:151-6. [PMID: 10871055 DOI: 10.1006/abbi.2000.1789] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Pancreastatin, a chromogranin A derived peptide, exerts a glycogenolytic effect on the hepatocyte. This effect is initiated by binding to membrane receptors which are coupled to pertussis toxin insensitive G proteins belonging to the Gq/11 family. We have recently solubilized active pancreastatin receptors from rat liver membranes still functionally coupled to G proteins. Here, we have purified pancreastatin receptors by a two-step procedure. First, pancreastatin receptors with their associated Gq/11 regulatory proteins were purified from liver membranes by lectin absorption chromatography on wheat germ agglutinin immobilized on agarose. A biotinylated rat pancreastatin analog was tested for binding to liver membranes before using it for affinity purification. Unlabeled biotinylated rat pancreastatin competed for 125I-labeled [Tyr0]PST binding to solubilized receptors with a Kd = 0.27 nM, comparable to that of native pancreastatin. The biotinylated analog was immobilized on streptavidin-coated Sepharose beads and used to further affinity purify wheat germ agglutinin eluted receptor material. Specific elution at low pH showed that the receptor protein was purified as an 80-kDa protein in association with a G protein of the q/11 family, as demonstrated by specific immunoblot analysis. The specificity of the receptor band was assessed by chemical cross-linking of the purified material followed by SDS-PAGE and autoradiography. In conclusion, we have purified pancreastatin receptor as a glycoprotein of 80 kDa physically associated with a Gq/11 protein.
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Affiliation(s)
- J Santos-Alvarez
- Department of Medical Biochemistry and Molecular Biology, School of Medicine, Virgen Macarena University Hospital, Seville, Spain
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González-Yanes C, Santos-Alvarez J, Sánchez-Margalet V. Characterization of pancreastatin receptors and signaling in adipocyte membranes. BIOCHIMICA ET BIOPHYSICA ACTA 1999; 1451:153-62. [PMID: 10446397 DOI: 10.1016/s0167-4889(99)00084-1] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Pancreastatin (PST), a chromogranin A derived peptide with an array of effects in different tissues, has a role as a counterregulatory hormone of insulin action in hepatocytes and adipocytes, regulating glucose, lipid and protein metabolism. We have previously characterized PST receptors and signaling in rat hepatocytes, in which PST functions as a calcium-mobilizing hormone. In the present work we have studied PST receptors as well as the signal transduction pathways generated upon PST binding in adipocyte membranes. First, we have characterized PST receptors using radiolabeled PST as a ligand. Analysis of binding data indicated the existence of one class of binding sites, with a B(max) of 5 fmol/mg of protein and a K(d) of 1 nM. In addition, we have studied the G protein system that couples the PST receptor by gamma-(35)S-GTP binding studies. We have found that two G protein systems are involved, pertussis toxin-sensitive and -insensitive respectively. Specific anti-G protein alpha subtype sera were used to block the effect of pancreastatin receptor activation. Galpha(q/11) and to a lesser extent Galpha(i1,2) are activated by PST in rat adipocyte membranes. On the other hand, adenylate cyclase activity was not affected by PST. Finally, we have studied the specific phospholipase C isoform that is activated in response to PST. We have found that PST receptor is coupled to PLC-beta(3) via Galpha(q/11) activation in adipocyte membranes.
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Affiliation(s)
- C González-Yanes
- Departamento de Bioquímica Médica y Biología Molecular, Facultad de Medicina, Unidad de Investigación del Hospital Universitario Virgen Macarena, Av. Sánchez Pizjuan 4, Sevilla 41009, Spain
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Santos-Alvarez J, Sánchez-Margalet V. G protein G alpha q/11 and G alpha i1,2 are activated by pancreastatin receptors in rat liver: studies with GTP-gamma 35S and azido-GTP-alpha-32P. J Cell Biochem 1999; 73:469-77. [PMID: 10733341 DOI: 10.1002/(sici)1097-4644(19990615)73:4<469::aid-jcb5>3.0.co;2-u] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In the liver, pancreastatin exerts a glycogenolytic effect through interaction with specific receptors, followed by activation of phospholipase C and guanylate cyclase. Pancreastatin receptor seems to be coupled to two different G protein systems: a pertussis toxin-insensitive G protein that mediates activation of phospholipase C, and a pertussis toxin sensitive G protein that mediates the cyclic GMP production. The aim of this study was to identify the specific G protein subtypes coupling pancreastatin receptors in rat liver membranes. GTP binding was determined by using gamma-35S-GTP; specific anti-G protein alpha subtype sera were used to block the effect of pancreastatin receptor activation. Activation of G proteins was demonstrated by the incorporation of the photoreactive GTP analogue 8-azido-alpha-32P-GTP into liver membranes and into specific immunoprecipitates of different Galpha subunits from soluble rat liver membranes. Pancreastatin stimulation of rat liver membranes increases the binding of gamma-35S-GTP in a time- and dose-dependent manner. Activation of the soluble receptors still led to the pancreastatin dose-dependent stimulation of gamma-35S-GTP binding. Besides, WGA semipurified receptors also stimulates GTP binding. The binding was inhibited by treatment with anti-Galphaq/11 (85%) and anti-Galphai1,2 (15%) sera, whereas anti-Galphao,i3 serum failed to affect the binding. Finally, pancreastatin stimulates GTP photolabeling of particulate membranes. Moreover, it specifically increased the incorporation of 8-azido-alpha-32P-GTP into Galphaq/11 and Galpha, but not into Galphao,i3 from soluble rat liver membranes. In conclusion, pancreastatin stimulation of rat liver membranes led to the activation of Galphaq/11 and Galphai1,2 proteins. These results suggest that Galphaq/11 and Galphai1,2 may play a functional role in the signaling of pancreastatin receptor by mediating the production of IP3 and cGMP respectively.
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Affiliation(s)
- J Santos-Alvarez
- Departamento de Bioquímica Médica y Biología Molecular, Facultad de Medicina, Hospital Universitario Virgen Macarena, Sevilla, Spain
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Sánchez-Margalet V, González-Yanes C. Pancreastatin inhibits insulin action in rat adipocytes. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:E1055-60. [PMID: 9843749 DOI: 10.1152/ajpendo.1998.275.6.e1055] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Pancreastatin (PST), a regulatory peptide with a general inhibitory effect on secretion, is derived from chromogranin A, a glycoprotein present throughout the neuroendocrine system. We have previously demonstrated the counterregulatory role of PST on insulin action in rat hepatocytes. Here, we are reporting the PST effects on rat adipocytes. PST dose dependently inhibits basal and insulin-stimulated glucose transport, lactate production, and lipogenesis, impairing the main metabolic actions of insulin in adipocytes. These effects were observed in a wide range of insulin concentrations, leading to a shift to the right in the dose-response curve. Maximal effect was observed at 10 nM PST, and the IC50 value was approximately 1 nM. Moreover, PST has a lipolytic effect in rat adipocytes (ED50 0.1 nM), although it was completely inhibited by insulin. In contrast, PST dose dependently stimulated protein synthesis and enhanced insulin-stimulated protein synthesis. In summary, these data show the lipokinetic effect of PST and the inhibitory effect of PST on insulin metabolic action within a range of physiological concentrations. Therefore, these results give new pathophysiological basis for the association of PST with insulin resistance.
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Affiliation(s)
- V Sánchez-Margalet
- Department of Medical Biochemistry and Molecular Biology, School of Medicine, Investigation Unit of the University Hospital Virgen Macarena, Seville 41009, Spain
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Santos-Alvarez J, Sánchez-Margalet V. Pancreastatin activates beta3 isoform of phospholipase C via G(alpha)11 protein stimulation in rat liver membranes. Mol Cell Endocrinol 1998; 143:101-6. [PMID: 9806354 DOI: 10.1016/s0303-7207(98)00137-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Pancreastatin (PST) receptors have been recently shown to mediate activation of phospholipase C (PLC) in rat liver membranes. There is evidence that the G protein that links pancreastatin receptor with PLC-beta is pertussis toxin-insensitive and belongs to the G(alpha)q family. Here, we have employed blocking antisera to sort out the specific PLC-beta isoform as well as the specific G(alpha) subunit activated by PST receptor in rat liver membranes. The presence of different PLC-beta isoforms was checked by immunoblot analysis. Only PLC-beta4 was not detected, whereas PLC-beta1, beta2 and beta3 were abundant in rat liver membranes. However, only anti-PLC-beta3 serum was able to block the PST receptor response. We also checked the expression of G(alpha)q and Galpha11 in rat liver membranes by immunoblot. Even though both isoforms were present. only anti-Galpha11 serum was able to block the PST receptor response. In order to check the specificity of the blocking antisera, we employed them to block the effect of ADP and thrombin stimulating PLC activity in platelet membranes, a system lacking Galpha11. Anti-G(alpha)q but not anti-Galpha11 sera were able to block the agonist stimulated PLC activity. These data suggest that PST receptor response is mediated by the activation of the beta3 isoform of PLC via Galpha11 protein stimulation in rat liver membranes.
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Affiliation(s)
- J Santos-Alvarez
- Department of Medical Biochemistry and Molecular Biology, School of Medicine, Investigation Unit of the Virgen Macarena University Hospital, Seville, Spain
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Santos-Alvarez J, González-Yanes C, Sánchez-Margalet V. Pancreastatin receptor is coupled to a guanosine triphosphate-binding protein of the G(q/11)alpha family in rat liver membranes. Hepatology 1998; 27:608-14. [PMID: 9462664 DOI: 10.1002/hep.510270240] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Pancreastatin (PST), a recently discovered regulatory peptide derived from chromogranin A, has been shown to have a glycogenolytic effect in the hepatocyte that is mediated by increasing intracellular calcium. Our previous studies on pancreastatin signaling suggested that PST receptor is coupled to some G proteins in the plasma membrane of the hepatocyte. The nature of this interaction was investigated using antisera against G(q/11)alpha by different approaches. Indirect evidence of a pertussis toxin (PT)-insensitive G protein of the family of G(q/11)alpha was obtained by measuring high-affinity guanosine triphosphatase (GTPase) activity in soluble rat liver membranes. PST increased GTPase activity in a dose-dependent manner. This effect was only slightly inhibited by PT pretreatment of the membranes, whereas anti-G(q/11)alpha antisera blocked most of the PST-stimulated GTPase activity. The selective association of the PST receptor with this G protein was further studied by the coelution in wheat germ agglutinin semipurification of the receptor and by immunoprecipitation of the G protein-PST receptor complexes using G-protein-specific antisera. A G protein of the family of G(q/11)alpha was found to be associated with the semipurified PST receptor. Moreover, anti-G(q/11)alpha antisera immunoprecipitated most PST-binding activity (95%), bringing down most of the specific G protein, whereas anti-G(il,2)alpha and -G(o,i3)alpha failed to immunoprecipitate the PST-binding activity. Finally, the coupling of the PST receptor with the effector phospholipase C was disrupted by blocking with G(q/11)alpha antisera, suggesting that a G protein of the family of G(q/11)alpha is a signal mediator from PST receptors to phospholipase C activation in rat liver membranes.
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Affiliation(s)
- J Santos-Alvarez
- Departamento de Bioquímica Médica y Biología Molecular, Facultad de Medicina, Unidad de Investigación Hospital Universitario Virgen Macarena, Universidad de Sevilla, Spain
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Sánchez-Margalet V, Santos-Alvarez J. Solubilization and molecular characterization of active pancreastatin receptors from rat liver membranes. Endocrinology 1997; 138:1712-8. [PMID: 9075735 DOI: 10.1210/endo.138.4.5075] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Pancreastatin receptors were solubilized from rat liver membranes with the nonionic detergent Triton X-100. Binding of a iodinated analog of rat pancreastatin ([125I-Tyr0]pancreastatin) to the soluble fraction was time dependent, saturable, and reversible. Scatchard analysis of binding under equilibrium conditions indicated that the soluble extracts contained a single class of pancreastatin-binding sites, with a binding capacity of 14 fmol/mg protein and a Kd of 0.3 nM. As observed with membrane-bound receptors, binding of [125I]pancreastatin to soluble extracts was inhibited by guanine nucleotides with the following rank order of potency: guanyl-5'-yl-imidodiphosphate > GTP > GDP > GMP, indicating that the soluble receptors are functionally linked to G proteins. Molecular analysis of the soluble pancreastatin receptor by covalent cross-linking to [125I]pancreastatin using disuccinimidyl suberate and further identification on SDS-PAGE indicated a single band of 85,000 Mr. Gel filtration of soluble extracts on Sephacryl S-300 revealed two molecular components with binding abilities (Mr 80,000 and 170,000). The higher molecular mass component was more sensitive to guanine nucleotides, and covalent cross-linking of both components to [125I]pancreastatin and further SDS-PAGE analysis revealed again a single band of 85,000 Mr, suggesting an association of the receptor with a G protein. Moreover, direct evidence that a Gq was present in the same chromatographic fraction was obtained by specific immunodetection. The soluble receptor is a glycoprotein that can be specifically bound to the wheat-germ agglutinin lectin. We conclude that we solubilized active pancreastatin receptors from rat liver membranes, and these results support the conclusion that the liver pancreastatin receptor consists of a 80,000 Mr glycoprotein associated with G proteins.
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Affiliation(s)
- V Sánchez-Margalet
- Department of Medical Biochemistry and Molecular Biology, Faculty of Medicine, University of Seville, Spain.
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Sánchez-Margalet V, Lucas M, Goberna R. Pancreastatin action in the liver: dual coupling to different G proteins. Cell Signal 1996; 8:9-12. [PMID: 8777144 DOI: 10.1016/0898-6568(95)02014-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Pancreastatin is a 49 amino acid peptide first isolated, purified and characterized from porcine pancreas. Its biological activity in different tissues can be assigned to the C-terminal part of the molecule. Pancreastatin has a prohormonal precursor, chromogranin A, which is a glycoprotein present in neuroendocrine cells, including the endocrine pancreas. We have been interested in pancreastatin action in the liver. We found that pancreastatin has a glycogenolytic effect in the hepatocyte both in vivo and in vitro. We then studied and characterized the specific pancreastatin receptor in the rat liver plasma membrane, as well as the specific signal transduction. This receptor appears to be coupled to two different G proteins. A pertussis toxin-insensitive G proteins leads to the activation of phospholipase C, and therefore mediates the glycogenolytic effect in the liver by increasing cytoplasmic free calcium and stimulating protein kinase C. The role of cyclic GMP in the action of pancreastatin is not known yet, although it seems to regulate negatively the activation of phospholipase C. The precise mechanism by which pancreastatin stimulates guanylate cyclase activity remains to be studied.
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Affiliation(s)
- V Sánchez-Margalet
- Departamento De Bioquímica Médica y Biología Molecular, Facultad De Medicina, Universidad De Sevilla, Hospital Universitario Virgen Macarena, Spain
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