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Glucagon stimulates exocytosis in mouse and rat pancreatic {alpha} cells by binding to glucagon receptors.

Ma, Xiaosong LU ; De Marinis, Yang LU ; Gromada, Jesper; Sewing, Sabine; Berggren, Per-Olof; Buschard, Karsten; Salehi, Albert; Vikman, Jenny LU ; Rorsman, Patrik LU and Eliasson, Lena LU (2005) In Molecular Endocrinology 19(1). p.198-212
Abstract
Glucagon, secreted by the pancreatic alpha-cells, stimulates insulin secretion from neighboring beta-cells by cAMP- and protein kinase A (PKA)-dependent mechanisms, but it is not known whether glucagon also modulates its own secretion. We have addressed this issue by combining recordings of membrane capacitance (to monitor exocytosis) in individual alpha-cells with biochemical assays of glucagon secretion and cAMP content in intact pancreatic islets, as well as analyses of glucagon receptor expression in pure alpha-cell fractions by RT-PCR. Glucagon stimulated cAMP generation and exocytosis dose dependently with an EC50 of 1.6-1.7 nm. The stimulation of both parameters plateaued at concentrations beyond 10 nm of glucagon where a more than... (More)
Glucagon, secreted by the pancreatic alpha-cells, stimulates insulin secretion from neighboring beta-cells by cAMP- and protein kinase A (PKA)-dependent mechanisms, but it is not known whether glucagon also modulates its own secretion. We have addressed this issue by combining recordings of membrane capacitance (to monitor exocytosis) in individual alpha-cells with biochemical assays of glucagon secretion and cAMP content in intact pancreatic islets, as well as analyses of glucagon receptor expression in pure alpha-cell fractions by RT-PCR. Glucagon stimulated cAMP generation and exocytosis dose dependently with an EC50 of 1.6-1.7 nm. The stimulation of both parameters plateaued at concentrations beyond 10 nm of glucagon where a more than 3-fold enhancement was observed. The actions of glucagon were unaffected by the GLP-1 receptor antagonist exendin-(9-39) but abolished by des-His1-[Glu9]-glucagon-amide, a specific blocker of the glucagon receptor. The effects of glucagon on alpha-cell exocytosis were mimicked by forskolin and the stimulatory actions of glucagon and forskolin on exocytosis were both reproduced by intracellular application of 0.1 mm cAMP. cAMP-potentiated exocytosis involved both PKA-dependent and -independent (resistant to Rp-cAMPS, an Rp-isomer of cAMP) mechanisms. The presence of the cAMP-binding protein cAMP-guanidine nucleotide exchange factor II in alpha-cells was documented by a combination of immunocytochemistry and RT-PCR and 8-(4-chloro-phenylthio)-2'-O-methyl-cAMP, a cAMP-guanidine nucleotide exchange factor II-selective agonist, mimicked the effect of cAMP and augmented rapid exocytosis in a PKA-independent manner. We conclude that glucagon released from the alpha-cells, in addition to its well-documented systemic effects and paracrine actions within the islet, also represents an autocrine regulator of alpha-cell function. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Molecular Endocrinology
volume
19
issue
1
pages
198 - 212
publisher
The Endocrine Society
external identifiers
  • wos:000225946500017
  • pmid:15459251
  • scopus:19944427738
ISSN
0888-8809
DOI
10.1210/me.2004-0059
language
English
LU publication?
yes
id
cea6b6db-157e-40e3-bbf8-ed28a7bc719b (old id 129958)
alternative location
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15459251&dopt=Abstract
date added to LUP
2007-07-17 11:31:40
date last changed
2017-10-01 04:40:34
@article{cea6b6db-157e-40e3-bbf8-ed28a7bc719b,
  abstract     = {Glucagon, secreted by the pancreatic alpha-cells, stimulates insulin secretion from neighboring beta-cells by cAMP- and protein kinase A (PKA)-dependent mechanisms, but it is not known whether glucagon also modulates its own secretion. We have addressed this issue by combining recordings of membrane capacitance (to monitor exocytosis) in individual alpha-cells with biochemical assays of glucagon secretion and cAMP content in intact pancreatic islets, as well as analyses of glucagon receptor expression in pure alpha-cell fractions by RT-PCR. Glucagon stimulated cAMP generation and exocytosis dose dependently with an EC50 of 1.6-1.7 nm. The stimulation of both parameters plateaued at concentrations beyond 10 nm of glucagon where a more than 3-fold enhancement was observed. The actions of glucagon were unaffected by the GLP-1 receptor antagonist exendin-(9-39) but abolished by des-His1-[Glu9]-glucagon-amide, a specific blocker of the glucagon receptor. The effects of glucagon on alpha-cell exocytosis were mimicked by forskolin and the stimulatory actions of glucagon and forskolin on exocytosis were both reproduced by intracellular application of 0.1 mm cAMP. cAMP-potentiated exocytosis involved both PKA-dependent and -independent (resistant to Rp-cAMPS, an Rp-isomer of cAMP) mechanisms. The presence of the cAMP-binding protein cAMP-guanidine nucleotide exchange factor II in alpha-cells was documented by a combination of immunocytochemistry and RT-PCR and 8-(4-chloro-phenylthio)-2'-O-methyl-cAMP, a cAMP-guanidine nucleotide exchange factor II-selective agonist, mimicked the effect of cAMP and augmented rapid exocytosis in a PKA-independent manner. We conclude that glucagon released from the alpha-cells, in addition to its well-documented systemic effects and paracrine actions within the islet, also represents an autocrine regulator of alpha-cell function.},
  author       = {Ma, Xiaosong and De Marinis, Yang and Gromada, Jesper and Sewing, Sabine and Berggren, Per-Olof and Buschard, Karsten and Salehi, Albert and Vikman, Jenny and Rorsman, Patrik and Eliasson, Lena},
  issn         = {0888-8809},
  language     = {eng},
  number       = {1},
  pages        = {198--212},
  publisher    = {The Endocrine Society},
  series       = {Molecular Endocrinology},
  title        = {Glucagon stimulates exocytosis in mouse and rat pancreatic {alpha} cells by binding to glucagon receptors.},
  url          = {http://dx.doi.org/10.1210/me.2004-0059},
  volume       = {19},
  year         = {2005},
}