Activation of Elk-1, an Ets transcription factor, by glucose and EGF treatment of insulinoma cells

Ernesto Bernal-Mizrachi, Wu Wen, Shanthi Srinivasan, Alison Klenk, David Cohen, M. Alan Permutt

Research output: Contribution to journalArticle

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Abstract

Elk-1, a member of the ternary complex factor family of Ets domain proteins that bind serum response elements, is activated by phosphorylation in a cell-specific manner in response to growth factors and other agents. The purpose of the current study was to determine whether Elk-1 activation contributes to glucose-/depolarization-induced Ca2+-dependent induction of immediate early response genes in pancreatic islet β-cells. The results of experiments in insulinoma (MIN6) cells demonstrated that Elk-1-binding sites (Ets elements) in the Egr-1 gene promoter contribute to transcriptional activation of the gene. Treatment with either epidermal growth factor (EGF), a known inducer of β-cell hyperplasia, glucose, or KCl-induced depolarization resulted in Ser383 phosphorylation and transcriptional activation of Elk-1 (4 ± 0.3-, P = 0.003, 2.3 ± 0.19-, P = 0.002, and 2.2 ± 0.1- fold, P = 0.001 respectively). The depolarization response was inhibited by the Ca2+ channel blocker verapamil and by the MEK inhibitor PD98059 (53 ± 6 and 55 ± 0.5%, respectively). EGF-induced activation of Elk-1 was also inhibited by PD98059 (60 ± 5%). A dominant negative Ras produced partial inhibition (42%) of the depolarization-induced Elk-1 transcriptional activation. Transfection with a constitutively active Ca2+/calmodulin kinase IV plasmid also resulted in Elk-1 transcriptional activation. Experiments with p38, phosphatidylinositol 3-kinase, and protein kinase A inhibitors indicated that these pathways are not involved. We conclude that Elk-1 activation contributes to glucose-/depolarization-induced Ca2+-dependent induction of immediate early growth response genes in pancreatic islet β-cells. Furthermore, the results demonstrated a convergence of nutrient- and growth factor-mediated signaling pathways on Elk-1 activation through induction of Ras/mitogen-activated protein kinase ERK-1 and -2. The role of these pathways in the glucose-induced proliferation of islet β-cells can now be assessed.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Endocrinology and Metabolism
Volume281
Issue number6 44-6
StatePublished - 2001

Fingerprint

ets-Domain Protein Elk-1
Proto-Oncogene Protein c-ets-1
Insulinoma
Islets of Langerhans
Epidermal Growth Factor
Chemical activation
Transcriptional Activation
Depolarization
Glucose
Genes
Intercellular Signaling Peptides and Proteins
Ternary Complex Factors
Phosphorylation
Serum Response Element
Phosphatidylinositol 3-Kinase
Calcium-Calmodulin-Dependent Protein Kinases
Immediate-Early Genes
Mitogen-Activated Protein Kinase Kinases
Protein Kinase Inhibitors
Verapamil

Keywords

  • Depolarization
  • Egr-1
  • Epidermal growth factor
  • Growth factors

ASJC Scopus subject areas

  • Physiology
  • Endocrinology
  • Biochemistry

Cite this

Activation of Elk-1, an Ets transcription factor, by glucose and EGF treatment of insulinoma cells. / Bernal-Mizrachi, Ernesto; Wen, Wu; Srinivasan, Shanthi; Klenk, Alison; Cohen, David; Alan Permutt, M.

In: American Journal of Physiology - Endocrinology and Metabolism, Vol. 281, No. 6 44-6, 2001.

Research output: Contribution to journalArticle

Bernal-Mizrachi, Ernesto ; Wen, Wu ; Srinivasan, Shanthi ; Klenk, Alison ; Cohen, David ; Alan Permutt, M. / Activation of Elk-1, an Ets transcription factor, by glucose and EGF treatment of insulinoma cells. In: American Journal of Physiology - Endocrinology and Metabolism. 2001 ; Vol. 281, No. 6 44-6.
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AU - Bernal-Mizrachi, Ernesto

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AU - Srinivasan, Shanthi

AU - Klenk, Alison

AU - Cohen, David

AU - Alan Permutt, M.

PY - 2001

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N2 - Elk-1, a member of the ternary complex factor family of Ets domain proteins that bind serum response elements, is activated by phosphorylation in a cell-specific manner in response to growth factors and other agents. The purpose of the current study was to determine whether Elk-1 activation contributes to glucose-/depolarization-induced Ca2+-dependent induction of immediate early response genes in pancreatic islet β-cells. The results of experiments in insulinoma (MIN6) cells demonstrated that Elk-1-binding sites (Ets elements) in the Egr-1 gene promoter contribute to transcriptional activation of the gene. Treatment with either epidermal growth factor (EGF), a known inducer of β-cell hyperplasia, glucose, or KCl-induced depolarization resulted in Ser383 phosphorylation and transcriptional activation of Elk-1 (4 ± 0.3-, P = 0.003, 2.3 ± 0.19-, P = 0.002, and 2.2 ± 0.1- fold, P = 0.001 respectively). The depolarization response was inhibited by the Ca2+ channel blocker verapamil and by the MEK inhibitor PD98059 (53 ± 6 and 55 ± 0.5%, respectively). EGF-induced activation of Elk-1 was also inhibited by PD98059 (60 ± 5%). A dominant negative Ras produced partial inhibition (42%) of the depolarization-induced Elk-1 transcriptional activation. Transfection with a constitutively active Ca2+/calmodulin kinase IV plasmid also resulted in Elk-1 transcriptional activation. Experiments with p38, phosphatidylinositol 3-kinase, and protein kinase A inhibitors indicated that these pathways are not involved. We conclude that Elk-1 activation contributes to glucose-/depolarization-induced Ca2+-dependent induction of immediate early growth response genes in pancreatic islet β-cells. Furthermore, the results demonstrated a convergence of nutrient- and growth factor-mediated signaling pathways on Elk-1 activation through induction of Ras/mitogen-activated protein kinase ERK-1 and -2. The role of these pathways in the glucose-induced proliferation of islet β-cells can now be assessed.

AB - Elk-1, a member of the ternary complex factor family of Ets domain proteins that bind serum response elements, is activated by phosphorylation in a cell-specific manner in response to growth factors and other agents. The purpose of the current study was to determine whether Elk-1 activation contributes to glucose-/depolarization-induced Ca2+-dependent induction of immediate early response genes in pancreatic islet β-cells. The results of experiments in insulinoma (MIN6) cells demonstrated that Elk-1-binding sites (Ets elements) in the Egr-1 gene promoter contribute to transcriptional activation of the gene. Treatment with either epidermal growth factor (EGF), a known inducer of β-cell hyperplasia, glucose, or KCl-induced depolarization resulted in Ser383 phosphorylation and transcriptional activation of Elk-1 (4 ± 0.3-, P = 0.003, 2.3 ± 0.19-, P = 0.002, and 2.2 ± 0.1- fold, P = 0.001 respectively). The depolarization response was inhibited by the Ca2+ channel blocker verapamil and by the MEK inhibitor PD98059 (53 ± 6 and 55 ± 0.5%, respectively). EGF-induced activation of Elk-1 was also inhibited by PD98059 (60 ± 5%). A dominant negative Ras produced partial inhibition (42%) of the depolarization-induced Elk-1 transcriptional activation. Transfection with a constitutively active Ca2+/calmodulin kinase IV plasmid also resulted in Elk-1 transcriptional activation. Experiments with p38, phosphatidylinositol 3-kinase, and protein kinase A inhibitors indicated that these pathways are not involved. We conclude that Elk-1 activation contributes to glucose-/depolarization-induced Ca2+-dependent induction of immediate early growth response genes in pancreatic islet β-cells. Furthermore, the results demonstrated a convergence of nutrient- and growth factor-mediated signaling pathways on Elk-1 activation through induction of Ras/mitogen-activated protein kinase ERK-1 and -2. The role of these pathways in the glucose-induced proliferation of islet β-cells can now be assessed.

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