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Nuclear translocation of an ICA512 cytosolic fragment couples granule exocytosis and insulin expression in {beta}-cells.

Trajkovski M, Mziaut H, Altkrüger A, Ouwendijk J, Knoch KP, Müller S, Solimena M - J. Cell Biol. (2004)

Bottom Line: Islet cell autoantigen 512 (ICA512)/IA-2 is a receptor tyrosine phosphatase-like protein associated with the insulin secretory granules (SGs) of pancreatic beta-cells.This cleavage occurs at the plasma membrane and generates an ICA512 cytosolic fragment that is targeted to the nucleus, where it binds the E3-SUMO ligase protein inhibitor of activated signal transducer and activator of transcription-y (PIASy) and up-regulates insulin expression.Accordingly, this novel pathway directly links regulated exocytosis of SGs and control of gene expression in beta-cells, whose impaired insulin production and secretion causes diabetes.

View Article: PubMed Central - PubMed

Affiliation: Experimental Diabetology, Carl Gustav Carus Medical School, Dresden University of Technology, Dresden, Germany.

ABSTRACT
Islet cell autoantigen 512 (ICA512)/IA-2 is a receptor tyrosine phosphatase-like protein associated with the insulin secretory granules (SGs) of pancreatic beta-cells. Here, we show that exocytosis of SGs and insertion of ICA512 in the plasma membrane promotes the Ca(2+)-dependent cleavage of ICA512 cytoplasmic domain by mu-calpain. This cleavage occurs at the plasma membrane and generates an ICA512 cytosolic fragment that is targeted to the nucleus, where it binds the E3-SUMO ligase protein inhibitor of activated signal transducer and activator of transcription-y (PIASy) and up-regulates insulin expression. Accordingly, this novel pathway directly links regulated exocytosis of SGs and control of gene expression in beta-cells, whose impaired insulin production and secretion causes diabetes.

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μ-Calpain is enriched at the plasma membrane. (A) Confocal microscopy of INS-1 cells double immunostained with anti–μ-calpain (pseudogreen) and anti-ICA512ecto (pseudored) antibodies. Bar, 10 μm. (B) Western blots with anti–μ-calpain, anti-ICA512, anti-CPE, and anti-Glut2 antibodies on INS-1 cell fractions separated on a continuous sucrose density gradient. The sucrose molarity of each fraction is indicated on the top. (C) Protein distribution in the fractions shown in B. The highest signal for each protein was equaled to 100%.
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fig2: μ-Calpain is enriched at the plasma membrane. (A) Confocal microscopy of INS-1 cells double immunostained with anti–μ-calpain (pseudogreen) and anti-ICA512ecto (pseudored) antibodies. Bar, 10 μm. (B) Western blots with anti–μ-calpain, anti-ICA512, anti-CPE, and anti-Glut2 antibodies on INS-1 cell fractions separated on a continuous sucrose density gradient. The sucrose molarity of each fraction is indicated on the top. (C) Protein distribution in the fractions shown in B. The highest signal for each protein was equaled to 100%.

Mentions: μ-Calpain is recruited to the plasma membrane and activated by Ca2+ and phospholipids, which are both implicated in neurosecretion (Martin, 1998; Wenk and De Camilli, 2004). In INS-1 cells, μ-calpain is mostly restricted to the cortical region (Fig. 2 A, left), where SGs are also enriched, as shown by staining for ICA512 (Fig. 2 A, middle). After subcellular fractionation, most μ-calpain is recovered in fractions containing the plasma membrane marker Glut-2 (Fig. 2, B and C), although a minor pool is found in the same fractions with ICA512-TMF and carboxypeptidase E (CPE), another marker of SGs.


Nuclear translocation of an ICA512 cytosolic fragment couples granule exocytosis and insulin expression in {beta}-cells.

Trajkovski M, Mziaut H, Altkrüger A, Ouwendijk J, Knoch KP, Müller S, Solimena M - J. Cell Biol. (2004)

μ-Calpain is enriched at the plasma membrane. (A) Confocal microscopy of INS-1 cells double immunostained with anti–μ-calpain (pseudogreen) and anti-ICA512ecto (pseudored) antibodies. Bar, 10 μm. (B) Western blots with anti–μ-calpain, anti-ICA512, anti-CPE, and anti-Glut2 antibodies on INS-1 cell fractions separated on a continuous sucrose density gradient. The sucrose molarity of each fraction is indicated on the top. (C) Protein distribution in the fractions shown in B. The highest signal for each protein was equaled to 100%.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2172607&req=5

fig2: μ-Calpain is enriched at the plasma membrane. (A) Confocal microscopy of INS-1 cells double immunostained with anti–μ-calpain (pseudogreen) and anti-ICA512ecto (pseudored) antibodies. Bar, 10 μm. (B) Western blots with anti–μ-calpain, anti-ICA512, anti-CPE, and anti-Glut2 antibodies on INS-1 cell fractions separated on a continuous sucrose density gradient. The sucrose molarity of each fraction is indicated on the top. (C) Protein distribution in the fractions shown in B. The highest signal for each protein was equaled to 100%.
Mentions: μ-Calpain is recruited to the plasma membrane and activated by Ca2+ and phospholipids, which are both implicated in neurosecretion (Martin, 1998; Wenk and De Camilli, 2004). In INS-1 cells, μ-calpain is mostly restricted to the cortical region (Fig. 2 A, left), where SGs are also enriched, as shown by staining for ICA512 (Fig. 2 A, middle). After subcellular fractionation, most μ-calpain is recovered in fractions containing the plasma membrane marker Glut-2 (Fig. 2, B and C), although a minor pool is found in the same fractions with ICA512-TMF and carboxypeptidase E (CPE), another marker of SGs.

Bottom Line: Islet cell autoantigen 512 (ICA512)/IA-2 is a receptor tyrosine phosphatase-like protein associated with the insulin secretory granules (SGs) of pancreatic beta-cells.This cleavage occurs at the plasma membrane and generates an ICA512 cytosolic fragment that is targeted to the nucleus, where it binds the E3-SUMO ligase protein inhibitor of activated signal transducer and activator of transcription-y (PIASy) and up-regulates insulin expression.Accordingly, this novel pathway directly links regulated exocytosis of SGs and control of gene expression in beta-cells, whose impaired insulin production and secretion causes diabetes.

View Article: PubMed Central - PubMed

Affiliation: Experimental Diabetology, Carl Gustav Carus Medical School, Dresden University of Technology, Dresden, Germany.

ABSTRACT
Islet cell autoantigen 512 (ICA512)/IA-2 is a receptor tyrosine phosphatase-like protein associated with the insulin secretory granules (SGs) of pancreatic beta-cells. Here, we show that exocytosis of SGs and insertion of ICA512 in the plasma membrane promotes the Ca(2+)-dependent cleavage of ICA512 cytoplasmic domain by mu-calpain. This cleavage occurs at the plasma membrane and generates an ICA512 cytosolic fragment that is targeted to the nucleus, where it binds the E3-SUMO ligase protein inhibitor of activated signal transducer and activator of transcription-y (PIASy) and up-regulates insulin expression. Accordingly, this novel pathway directly links regulated exocytosis of SGs and control of gene expression in beta-cells, whose impaired insulin production and secretion causes diabetes.

Show MeSH
Related in: MedlinePlus