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Characterization and functional role of voltage gated cation conductances in the glucagon-like peptide-1 secreting GLUTag cell line

Reimann, F. ; Maziarz, M. LU orcid ; Flock, G. ; Habib, A. M. ; Drucker, D. J. and Gribble, F. M. (2005) In Journal of Physiology 563(1). p.161-175
Abstract

Glucagon-like peptide-1 (GLP-1) is released from intestinal L-cells in response to nutrient ingestion. It is currently under therapeutic evaluation because it enhances insulin secretion in type 2 diabetes. Previous studies using the GLP-1 secreting cell line GLUTag have shown that the cells are electrically active, and that the action potential frequency is regulated by nutrients. In this study we characterize voltage gated currents underlying this electrical activity and correlate the electrophysiological findings with gene expression determined by microarrays. Whole cell voltage clamp experiments designed to separate different ionic components revealed rapidly inactivating sodium currents sensitive to tetrodotoxin, calcium currents... (More)

Glucagon-like peptide-1 (GLP-1) is released from intestinal L-cells in response to nutrient ingestion. It is currently under therapeutic evaluation because it enhances insulin secretion in type 2 diabetes. Previous studies using the GLP-1 secreting cell line GLUTag have shown that the cells are electrically active, and that the action potential frequency is regulated by nutrients. In this study we characterize voltage gated currents underlying this electrical activity and correlate the electrophysiological findings with gene expression determined by microarrays. Whole cell voltage clamp experiments designed to separate different ionic components revealed rapidly inactivating sodium currents sensitive to tetrodotoxin, calcium currents sensitive to nifedipine and ω-conotoxin GVIA, and sustained as well as rapidly inactivating potassium currents, which were sensitive to TEA and 4-AP, respectively. In perforated patch experiments we also observed hyperpolarization-activated currents which were inhibited by ZD7288. The amplitude of the sodium current was ∼ 10 times that of the other depolarizing currents and tetrodotoxin abolished action potential firing. In secretion experiments, however, nifedipine, but not tetrodotoxin, ω-conotoxin GVIA or ZD7288, inhibited glucose-induced GLP-1 release. Consistent with this finding, the intracellular Ca2+ response to glucose was impaired by nifedipine but not by tetrodotoxin. Thus, in GLUTag cells, GLP-1 release is not dependent on the firing of Na+-carrying action potentials but requires membrane depolarization and Ca2+ entry through L-type Ca2+ channels. Understanding the characteristics of the currents and the molecular identification of the underlying channels in GLP-1 secreting cells might facilitate the development of agents to enhance GLP-1 secretion in vivo.

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author
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publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Physiology
volume
563
issue
1
pages
15 pages
publisher
The Physiological Society
external identifiers
  • pmid:15611035
  • scopus:14844321558
ISSN
0022-3751
DOI
10.1113/jphysiol.2004.076414
language
English
LU publication?
no
id
c0214818-3eef-4962-812e-0aa1c4f6ba88
date added to LUP
2019-08-05 13:19:47
date last changed
2024-09-04 06:43:30
@article{c0214818-3eef-4962-812e-0aa1c4f6ba88,
  abstract     = {{<p>Glucagon-like peptide-1 (GLP-1) is released from intestinal L-cells in response to nutrient ingestion. It is currently under therapeutic evaluation because it enhances insulin secretion in type 2 diabetes. Previous studies using the GLP-1 secreting cell line GLUTag have shown that the cells are electrically active, and that the action potential frequency is regulated by nutrients. In this study we characterize voltage gated currents underlying this electrical activity and correlate the electrophysiological findings with gene expression determined by microarrays. Whole cell voltage clamp experiments designed to separate different ionic components revealed rapidly inactivating sodium currents sensitive to tetrodotoxin, calcium currents sensitive to nifedipine and ω-conotoxin GVIA, and sustained as well as rapidly inactivating potassium currents, which were sensitive to TEA and 4-AP, respectively. In perforated patch experiments we also observed hyperpolarization-activated currents which were inhibited by ZD7288. The amplitude of the sodium current was ∼ 10 times that of the other depolarizing currents and tetrodotoxin abolished action potential firing. In secretion experiments, however, nifedipine, but not tetrodotoxin, ω-conotoxin GVIA or ZD7288, inhibited glucose-induced GLP-1 release. Consistent with this finding, the intracellular Ca<sup>2+</sup> response to glucose was impaired by nifedipine but not by tetrodotoxin. Thus, in GLUTag cells, GLP-1 release is not dependent on the firing of Na<sup>+</sup>-carrying action potentials but requires membrane depolarization and Ca<sup>2+</sup> entry through L-type Ca<sup>2+</sup> channels. Understanding the characteristics of the currents and the molecular identification of the underlying channels in GLP-1 secreting cells might facilitate the development of agents to enhance GLP-1 secretion in vivo.</p>}},
  author       = {{Reimann, F. and Maziarz, M. and Flock, G. and Habib, A. M. and Drucker, D. J. and Gribble, F. M.}},
  issn         = {{0022-3751}},
  language     = {{eng}},
  month        = {{02}},
  number       = {{1}},
  pages        = {{161--175}},
  publisher    = {{The Physiological Society}},
  series       = {{Journal of Physiology}},
  title        = {{Characterization and functional role of voltage gated cation conductances in the glucagon-like peptide-1 secreting GLUTag cell line}},
  url          = {{http://dx.doi.org/10.1113/jphysiol.2004.076414}},
  doi          = {{10.1113/jphysiol.2004.076414}},
  volume       = {{563}},
  year         = {{2005}},
}