uu.seUppsala University Publications
Change search
Link to record
Permanent link

Direct link
BETA
Alternative names
Publications (10 of 57) Show all publications
Gucek, A., Gandasi, N. R., Omar-Hmeadi, M., Bakke, M., Doskeland, S. O., Tengholm, A. & Barg, S. (2019). Fusion pore regulation by cAMP/Epac2 controls cargo release during insulin exocytosis. eLIFE, 8, Article ID e41711.
Open this publication in new window or tab >>Fusion pore regulation by cAMP/Epac2 controls cargo release during insulin exocytosis
Show others...
2019 (English)In: eLIFE, E-ISSN 2050-084X, Vol. 8, article id e41711Article in journal (Refereed) Published
Abstract [en]

Regulated exocytosis establishes a narrow fusion pore as initial aqueous connection to the extracellular space, through which small transmitter molecules such as ATP can exit. Co-release of polypeptides and hormones like insulin requires further expansion of the pore. There is evidence that pore expansion is regulated and can fail in diabetes and neurodegenerative disease. Here, we report that the cAMP-sensor Epac2 (Rap-GEF4) controls fusion pore behavior by acutely recruiting two pore-restricting proteins, amisyn and dynamin-1, to the exocytosis site in insulin-secreting beta-cells. cAMP elevation restricts and slows fusion pore expansion and peptide release, but not when Epac2 is inactivated pharmacologically or in Epac2(-/-) (Rapgef4(-/-)) mice. Consistently, overexpression of Epac2 impedes pore expansion. Widely used antidiabetic drugs (GLP-1 receptor agonists and sulfonylureas) activate this pathway and thereby paradoxically restrict hormone release. We conclude that Epac2/cAMP controls fusion pore expansion and thus the balance of hormone and transmitter release during insulin granule exocytosis.

Place, publisher, year, edition, pages
ELIFE SCIENCES PUBLICATIONS LTD, 2019
National Category
Cell Biology
Identifiers
urn:nbn:se:uu:diva-389824 (URN)10.7554/eLife.41711 (DOI)000471123300001 ()31099751 (PubMedID)
Funder
Novo NordiskSwedish Research Council, 2014-02575Swedish Research Council, 2017-00956Swedish Research Council, 2018-02871Ernfors FoundationSwedish Society for Medical Research (SSMF)The Research Council of NorwaySwedish Diabetes AssociationEXODIAB - Excellence of Diabetes Research in SwedenThe Swedish Brain Foundation
Available from: 2019-07-29 Created: 2019-07-29 Last updated: 2019-07-29Bibliographically approved
Yu, Q., Shuai, H., Ahooghalandari, P., Gylfe, E. & Tengholm, A. (2019). Glucose controls glucagon secretion by directly modulating cAMP in alpha cells. Diabetologia, 62(7), 1212-1224
Open this publication in new window or tab >>Glucose controls glucagon secretion by directly modulating cAMP in alpha cells
Show others...
2019 (English)In: Diabetologia, ISSN 0012-186X, E-ISSN 1432-0428, Vol. 62, no 7, p. 1212-1224Article in journal (Refereed) Published
Abstract [en]

Aims/hypothesis

Glucagon is critical for normal glucose homeostasis and aberrant secretion of the hormone aggravates dysregulated glucose control in diabetes. However, the mechanisms by which glucose controls glucagon secretion from pancreatic alpha cells remain elusive. The aim of this study was to investigate the role of the intracellular messenger cAMP in alpha-cell-intrinsic glucose regulation of glucagon release.

Methods

Subplasmalemmal cAMP and Ca2+ concentrations were recorded in isolated and islet-located alpha cells using fluorescent reporters and total internal reflection microscopy. Glucagon secretion from mouse islets was measured using ELISA.

Results

Glucose induced Ca2+-independent alterations of the subplasmalemmal cAMP concentration in alpha cells that correlated with changes in glucagon release. Glucose-lowering-induced stimulation of glucagon secretion thus corresponded to an elevation in cAMP that was independent of paracrine signalling from insulin or somatostatin. Imposed cAMP elevations stimulated glucagon secretion and abolished inhibition by glucose elevation, while protein kinase A inhibition mimicked glucose suppression of glucagon release.

Conclusions/interpretation

Glucose concentrations in the hypoglycaemic range control glucagon secretion by directly modulating the cAMP concentration in alpha cells independently of paracrine influences. These findings define a novel mechanism for glucose regulation of glucagon release that underlies recovery from hypoglycaemia and may be disturbed in diabetes.

Keywords
Ca2+, Cyclic AMP, Glucagon release, Hypoglycaemia, Insulin, Pancreatic alpha cell, Protein kinase A, Somatostatin
National Category
Endocrinology and Diabetes
Identifiers
urn:nbn:se:uu:diva-388762 (URN)10.1007/s00125-019-4857-6 (DOI)000471176200012 ()30953108 (PubMedID)
Funder
Swedish Research CouncilErnfors FoundationNovo NordiskSwedish Diabetes AssociationEXODIAB - Excellence of Diabetes Research in Sweden
Available from: 2019-08-13 Created: 2019-08-13 Last updated: 2019-08-14Bibliographically approved
Mojtaba Ghiasi, S., Dahlby, T., Hede Andersen, C., Haataja, L., Petersen, S., Omar-Hmeadi, M., . . . Tomasz Marzec, M. (2019). The Endoplasmic Reticulum Chaperone Glucose-Regulated Protein 94 is Essential for Proinsulin Handling. Diabetes, 68(4), 747-760
Open this publication in new window or tab >>The Endoplasmic Reticulum Chaperone Glucose-Regulated Protein 94 is Essential for Proinsulin Handling
Show others...
2019 (English)In: Diabetes, ISSN 0012-1797, E-ISSN 1939-327X, Vol. 68, no 4, p. 747-760Article in journal (Refereed) Published
Abstract [en]

Although endoplasmic reticulum (ER) chaperone binding to mutant proinsulin has been reported, the role of protein chaperones in the handling of wild-type proinsulin is under-investigated. Here, we have explored the importance of glucose regulated protein 94 (GRP94), a prominent ER chaperone known to fold insulin-like growth factors, in proinsulin handling within β-cells. We found that GRP94 co-immunoprecipitated with proinsulin and that inhibition of GRP94 function and/or expression reduced glucose-dependent insulin secretion, shortened proinsulin half-life and lowered intracellular proinsulin and insulin levels. This phenotype was accompanied by post-ER proinsulin misprocessing and higher numbers of enlarged insulin granules that contained amorphic material with reduced immunogold staining for mature insulin. Insulin granule exocytosis was two-fold accelerated but the secreted insulin had diminished bioactivity. Moreover, GRP94 knockdown or knockout in β-cells selectively activated Protein Kinase R-like Endoplasmic Reticulum Kinase (PERK), without increasing apoptosis levels. Finally, GRP94 mRNA was overexpressed in islets from T2D patients. We conclude that GRP94 is a chaperone crucial for proinsulin handling and insulin secretion.

National Category
Cell and Molecular Biology Endocrinology and Diabetes
Identifiers
urn:nbn:se:uu:diva-378915 (URN)10.2337/db18-0671 (DOI)000462053100007 ()30670477 (PubMedID)
Funder
Swedish Research Council
Available from: 2019-03-08 Created: 2019-03-08 Last updated: 2019-05-06Bibliographically approved
Wang, X., Jiang, L., Wallerman, O., Younis, S., Yu, Q., Klaesson, A., . . . Andersson, L. (2019). ZBED6 negatively regulates insulin production, neuronal differentiation, and cell aggregation in MIN6 cells. The FASEB Journal, 33(1), 88-100
Open this publication in new window or tab >>ZBED6 negatively regulates insulin production, neuronal differentiation, and cell aggregation in MIN6 cells
Show others...
2019 (English)In: The FASEB Journal, ISSN 0892-6638, E-ISSN 1530-6860, Vol. 33, no 1, p. 88-100Article in journal (Refereed) Published
Abstract [en]

Zinc finger BED domain containing protein 6 (Zbed6) has evolved from a domesticated DNA transposon and encodes a transcription factor unique to placental mammals. The aim of the present study was to investigate further the role of ZBED6 in insulin-producing cells, using mouse MIN6 cells, and to evaluate the effects of Zbed6 knockdown on basal -cell functions, such as morphology, transcriptional regulation, insulin content, and release. Zbed6-silenced cells and controls were characterized with a range of methods, including RNA sequencing, chromatin immunoprecipitation sequencing, insulin content and release, subplasma membrane Ca2+ measurements, cAMP determination, and morphologic studies. More than 700 genes showed differential expression in response to Zbed6 knockdown, which was paralleled by increased capacity to generate cAMP, as well as by augmented subplasmalemmal calcium concentration and insulin secretion in response to glucose stimulation. We identified >4000 putative ZBED6-binding sites in the MIN6 genome, with an enrichment of ZBED6 sites at upregulated genes, such as the -cell transcription factors v-maf musculoaponeurotic fibrosarcoma oncogene homolog A and Nk6 homeobox 1. We also observed altered morphology/growth patterns, as indicated by increased cell clustering, and in the appearance of axon-like Neurofilament, medium polypeptide and tubulin 3, class III-positive protrusions. We conclude that ZBED6 acts as a transcriptional regulator in MIN6 cells and that its activity suppresses insulin production, cell aggregation, and neuronal-like differentiation.Wang, X., Jiang, L., Wallerman, O., Younis, S., Yu, Q., Klaesson, A., Tengholm, A., Welsh, N., Andersson, L. ZBED6 negatively regulates insulin production, neuronal differentiation, and cell aggregation in MIN6 cells.

Place, publisher, year, edition, pages
FEDERATION AMER SOC EXP BIOL, 2019
Keywords
-cells, cell adhesion, transcriptome analysis, ChIP-seq
National Category
Cell and Molecular Biology
Identifiers
urn:nbn:se:uu:diva-377365 (URN)10.1096/fj.201600835R (DOI)000457401500007 ()29957057 (PubMedID)
Funder
Swedish Research Council, 80576801Swedish Research Council, 70374401Swedish Research CouncilKnut and Alice Wallenberg FoundationSwedish Child Diabetes FoundationNovo NordiskErnfors FoundationSwedish Diabetes Association
Available from: 2019-02-19 Created: 2019-02-19 Last updated: 2019-02-19Bibliographically approved
Yang, M., Idevall-Hagren, O., Gylfe, E. & Tengholm, A. (2018). A genetically encoded low-affinity Ca2+ sensor unmasks autocrine purinergic signalling in beta cells. Paper presented at 54th Annual Meeting of the European-Association-for-the-Study-of-Diabetes (EASD), OCT 01-05, 2018, Berlin, GERMANY. Diabetologia, 61, S196-S197
Open this publication in new window or tab >>A genetically encoded low-affinity Ca2+ sensor unmasks autocrine purinergic signalling in beta cells
2018 (English)In: Diabetologia, ISSN 0012-186X, E-ISSN 1432-0428, Vol. 61, p. S196-S197Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
Springer, 2018
National Category
Endocrinology and Diabetes
Identifiers
urn:nbn:se:uu:diva-367135 (URN)000443556002189 ()
Conference
54th Annual Meeting of the European-Association-for-the-Study-of-Diabetes (EASD), OCT 01-05, 2018, Berlin, GERMANY
Available from: 2018-11-29 Created: 2018-11-29 Last updated: 2018-11-29Bibliographically approved
Korol, S. V., Jin, Z., Jin, Y., Bhandage, A. K., Tengholm, A., Gandasi, N. R., . . . Birnir, B. (2018). Functional Characterization of Native, High-Affinity GABAA Receptors in Human Pancreatic β Cells. EBioMedicine, 30
Open this publication in new window or tab >>Functional Characterization of Native, High-Affinity GABAA Receptors in Human Pancreatic β Cells
Show others...
2018 (English)In: EBioMedicine, ISSN 0360-0637, E-ISSN 2352-3964, Vol. 30Article in journal (Refereed) Published
Abstract [en]

In human pancreatic islets, the neurotransmitter γ-aminobutyric acid (GABA) is an extracellular signaling molecule synthesized by and released from the insulin-secreting β cells. The effective, physiological GABA concentration range within human islets is unknown. Here we use native GABAA receptors in human islet β cells as biological sensors and reveal that 100-1000nM GABA elicit the maximal opening frequency of the single-channels. In saturating GABA, the channels desensitized and stopped working. GABA modulated insulin exocytosis and glucose-stimulated insulin secretion. GABAA receptor currents were enhanced by the benzodiazepine diazepam, the anesthetic propofol and the incretin glucagon-like peptide-1 (GLP-1) but not affected by the hypnotic zolpidem. In type 2 diabetes (T2D) islets, single-channel analysis revealed higher GABA affinity of the receptors. The findings reveal unique GABAA receptors signaling in human islets β cells that is GABA concentration-dependent, differentially regulated by drugs, modulates insulin secretion and is altered in T2D.

Keywords
GABA, GABA(A) receptor, Pancreatic islet, Type 2 diabetes
National Category
Other Medical Sciences not elsewhere specified Endocrinology and Diabetes
Identifiers
urn:nbn:se:uu:diva-348267 (URN)10.1016/j.ebiom.2018.03.014 (DOI)000430303000032 ()29606630 (PubMedID)
Funder
Swedish Research Council, 521-2009-4021EXODIAB - Excellence of Diabetes Research in SwedenSwedish Child Diabetes FoundationSwedish Diabetes AssociationNovo NordiskSwedish Society for Medical Research (SSMF)Swedish Research Council, 521-2012-1789Swedish Research Council, 2015-02417Swedish Research Council, 2017-00956Swedish Research Council, 2014-2575
Note

De 2 första författarna delar förstaförfattarskapet.

Available from: 2018-04-11 Created: 2018-04-11 Last updated: 2018-06-19Bibliographically approved
Tengholm, A. & Gylfe, E. (2017). cAMP signalling in insulin and glucagon secretion. Diabetes, obesity and metabolism, 19, 42-53
Open this publication in new window or tab >>cAMP signalling in insulin and glucagon secretion
2017 (English)In: Diabetes, obesity and metabolism, ISSN 1462-8902, E-ISSN 1463-1326, Vol. 19, p. 42-53Article, review/survey (Refereed) Published
Abstract [en]

The second messenger archetype cAMP is one of the most important cellular signalling molecules with central functions including the regulation of insulin and glucagon secretion from the pancreatic - and -cells, respectively. cAMP is generally considered as an amplifier of insulin secretion triggered by Ca2+ elevation in the -cells. Both messengers are also positive modulators of glucagon release from -cells, but in this case cAMP may be the important regulator and Ca2+ have a more permissive role. The actions of cAMP are mediated by protein kinase A (PKA) and the guanine nucleotide exchange factor Epac. The present review focuses on how cAMP is regulated by nutrients, hormones and neural factors in - and -cells via adenylyl cyclase-catalysed generation and phosphodiesterase-mediated degradation. We will also discuss how PKA and Epac affect ion fluxes and the secretory machinery to transduce the stimulatory effects on insulin and glucagon secretion. Finally, we will briefly describe disturbances of the cAMP system associated with diabetes and how cAMP signalling can be targeted to normalize hypo- and hypersecretion of insulin and glucagon, respectively, in diabetic patients.

Keywords
beta-cell, glucagon, incretins, insulin secretion, islets, type 2 diabetes
National Category
Endocrinology and Diabetes
Identifiers
urn:nbn:se:uu:diva-346513 (URN)10.1111/dom.12993 (DOI)000409452500005 ()28466587 (PubMedID)
Funder
Swedish Research Council, 2012‐6778
Available from: 2018-03-19 Created: 2018-03-19 Last updated: 2018-03-19Bibliographically approved
Alenkvist, I., Gandasi, N. R., Barg, S. & Tengholm, A. (2017). Recruitment of Epac2A to Insulin Granule Docking Sites Regulates Priming for Exocytosis. Diabetes, 66(10), 2610-2622
Open this publication in new window or tab >>Recruitment of Epac2A to Insulin Granule Docking Sites Regulates Priming for Exocytosis
2017 (English)In: Diabetes, ISSN 0012-1797, E-ISSN 1939-327X, Vol. 66, no 10, p. 2610-2622Article in journal (Refereed) Published
Abstract [en]

Epac is a cAMP-activated guanine nucleotide exchange factor that mediates cAMP signaling in various types of cells, including -cells, where it is involved in the control of insulin secretion. Upon activation, the protein redistributes to the plasma membrane, but the underlying molecular mechanisms and functional consequences are unclear. Using quantitative high-resolution microscopy, we found that cAMP elevation caused rapid binding of Epac2A to the -cell plasma membrane, where it accumulated specifically at secretory granules and rendered them more prone to undergo exocytosis. cAMP-dependent membrane binding required the high-affinity cyclic nucleotide-binding (CNB) and Ras association domains, but not the disheveled-Egl-10-pleckstrin domain. Although the N-terminal low-affinity CNB domain (CNB-A) was dispensable for the translocation to the membrane, it was critical for directing Epac2A to the granule sites. Epac1, which lacks the CNB-A domain, was recruited to the plasma membrane but did not accumulate at granules. We conclude that Epac2A controls secretory granule release by binding to the exocytosis machinery, an effect that is enhanced by prior cAMP-dependent accumulation of the protein at the plasma membrane.

National Category
Clinical Medicine
Identifiers
urn:nbn:se:uu:diva-336299 (URN)10.2337/db17-0050 (DOI)000411195800009 ()28679628 (PubMedID)
Note

De två första författarna delar förstaförfattarskapet.

Available from: 2018-01-23 Created: 2018-01-23 Last updated: 2018-01-23Bibliographically approved
Yu, Q., Shuai, H., Ahooghalandari, P., Gylfe, E. & Tengholm, A. (2016). Glucose lowers cAMP to inhibit glucagon secretion by a direct effect on alpha cells. Paper presented at 52nd Annual Meeting of the European-Association-for-the-Study-of-Diabetes (EASD), SEP 12-16, 2016, Munich, GERMANY. Diabetologia, 59, S266-S267
Open this publication in new window or tab >>Glucose lowers cAMP to inhibit glucagon secretion by a direct effect on alpha cells
Show others...
2016 (English)In: Diabetologia, ISSN 0012-186X, E-ISSN 1432-0428, Vol. 59, p. S266-S267Article in journal (Refereed) Published
Place, publisher, year, edition, pages
SPRINGER, 2016
National Category
Endocrinology and Diabetes
Identifiers
urn:nbn:se:uu:diva-322056 (URN)000398373701362 ()
Conference
52nd Annual Meeting of the European-Association-for-the-Study-of-Diabetes (EASD), SEP 12-16, 2016, Munich, GERMANY
Available from: 2017-05-16 Created: 2017-05-16 Last updated: 2017-05-16Bibliographically approved
Tuomi, T., Nagorny, C. L. F., Singh, P., Bennet, H., Yu, Q., Alenkvist, I., . . . Mulder, H. (2016). Increased Melatonin Signaling Is a Risk Factor for Type 2 Diabetes. Cell Metabolism, 23(6), 1067-1077
Open this publication in new window or tab >>Increased Melatonin Signaling Is a Risk Factor for Type 2 Diabetes
Show others...
2016 (English)In: Cell Metabolism, ISSN 1550-4131, E-ISSN 1932-7420, Vol. 23, no 6, p. 1067-1077Article in journal (Refereed) Published
Abstract [en]

Type 2 diabetes (T2D) is a global pandemic. Genome-wide association studies (GWASs) have identified >100 genetic variants associated with the disease, including a common variant in the melatonin receptor 1 b gene (MTNR1B). Here, we demonstrate increased MTNR1B expression in human islets from risk G-allele carriers, which likely leads to a reduction in insulin release, increasing T2D risk. Accordingly, in insulin-secreting cells, melatonin reduced cAMP levels, and MTNR1B overexpression exaggerated the inhibition of insulin release exerted by melatonin. Conversely, mice with a disruption of the receptor secreted more insulin. Melatonin treatment in a human recall-by-genotype study reduced insulin secretion and raised glucose levels more extensively in risk G-allele carriers. Thus, our data support a model where enhanced melatonin signaling in islets reduces insulin secretion, leading to hyperglycemia and greater future risk of T2D. The findings also imply that melatonin physiologically serves to inhibit nocturnal insulin release.

National Category
Endocrinology and Diabetes
Identifiers
urn:nbn:se:uu:diva-299571 (URN)10.1016/j.cmet.2016.04.009 (DOI)000378000600019 ()27185156 (PubMedID)
Funder
Swedish Research Council, 349-2006-237 2009-1039 521-2010-3490 521-2012-1743 521-2012-2119 325-2012-6778EU, European Research Council, 299045Swedish Diabetes AssociationNovo Nordisk
Available from: 2016-07-22 Created: 2016-07-22 Last updated: 2017-11-28Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-4508-0836

Search in DiVA

Show all publications