Valproate Prevents a Cytosolic vH
            +
            ATPase Subunit Insertion on Insulin Granule Membrane and Compromises Insulin Release in Min6 Cells

Sulfonylurea and glinide drugs display different effects on insulin granule motion in single β-cells in vitro. We therefore investigated the different effects that these drugs manifest towards insulin release in an in vivo long-term treatment model. Diabetic GK (Goto-Kakizaki) rats were treated with nateglinide, glibenclamide or insulin for 6 weeks. Insulin granule motion in single β-cells and the expression of SNARE (soluble N-ethylmaleimide-sensitive factor-attachment protein receptor) proteins were then analysed. Perifusion studies showed that decreased first-phase insulin release was partially recovered when GK rats were treated with nateglinide or insulin for 6 weeks, whereas no first-phase release occurred with glibenclamide treatment. In accord with the perifusion results, TIRF (total internal reflection fluorescence) imaging of insulin exocytosis showed restoration of the decreased number of docked insulin granules and the fusion events from them during first-phase release for nateglinide or insulin, but not glibenclamide, treatment; electron microscopy results confirmed the TIRF microscopy data. Relative to vehicle-treated GK β-cells, an increased number of SNARE clusters were evident in nateglinide- or insulin-treated cells; a lesser increase was observed in glibenclamide-treated cells. Immunostaining for insulin showed that nateglinide treatment better preserved pancreatic islet morphology than did glibenclamide treatment. However, direct exposure of GK β-cells to these drugs could not restore the decreased first-phase insulin release nor the reduced numbers of docked insulin granules. We conclude that treatment of GK rats with nateglinide and glibenclamide varies in long-term effects on β-cell functions; nateglinide treatment appears overall to be more beneficial.

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Demonstration of a proton gradient across the insulin granule membrane

Acta Physiologica Scandinavica ◽

10.1111/j.1748-1716.1980.tb06573.x ◽

1980 ◽

Vol 109 (1) ◽

pp. 113-114 ◽

Cited By ~ 15

Author(s):

HÅKAN ABRAHAMSSON ◽

ERIK GYLFE

Keyword(s):

Proton Gradient ◽

Granule Membrane ◽

Insulin Granule

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PPAR-γ overexpression suppresses glucose-induced proinsulin biosynthesis and insulin release synergistically with pioglitazone in MIN6 cells

Biochemical and Biophysical Research Communications ◽

10.1016/s0006-291x(03)01045-3 ◽

2003 ◽

Vol 306 (4) ◽

pp. 832-836 ◽

Cited By ~ 19

Author(s):

Yoko Nakamichi ◽

Toshiteru Kikuta ◽

Eisuke Ito ◽

Mica Ohara-Imaizumi ◽

Chiyono Nishiwaki ◽

...

Keyword(s):

Insulin Release ◽

Min6 Cells ◽

Proinsulin Biosynthesis ◽

Ppar Γ

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Nucleotide and bivalent cation specificity of the insulin-granule proton translocase

Biochemical Journal ◽

10.1042/bj2100235 ◽

1983 ◽

Vol 210 (1) ◽

pp. 235-242 ◽

Cited By ~ 5

Author(s):

J C Hutton ◽

M Peshavaria

Keyword(s):

Atp Hydrolysis ◽

Secretory Granules ◽

Bivalent Cation ◽

Nucleotide Hydrolysis ◽

Storage Vesicles ◽

Carbonyl Cyanide ◽

Granule Membrane ◽

Insulin Granule ◽

Intracellular Storage ◽

Adrenal Chromaffin

1. The nucleotide and bivalent cation specificity of the proton translocase activity of insulin secretory granules was investigated by assessing the inhibitor-sensitive rates of nucleotide hydrolysis by these organelles in relation to their chemiosmotic properties. 2. The relative rates of nucleotide hydrolysis by freeze/thawed granule preparations were: Mg2+ATP (100%) greater than Mg2+GTP (55%) greater than Mg2+UTP (48%) greater than Mg2+ITP (44%) greater than Mg2+CTP (23%) greater than Mg2+TTP (20%), and by intact granules were: Mg2+ATP (100%) greater than Mg2+ITP (74%) greater than Mg2+GTP (60%) greater than Mg2+CTP (35%). Mg2+ATP, Mg2+GTP and Mg2+ITP hydrolyses were inhibited by tributyltin and stimulated, in intact granules, by the protonophore carbonyl cyanide p-trifluoromethoxyphenylhydrazone; Mg2+CTP hydrolysis was not markedly affected by these compounds. Correspondingly, only Mg2+ATP, Mg2+GTP and Mg2+ITP produced large changes in the delta psi and delta mu H+ across the granule membrane. 3. The relative rates of maximal ATPase activity stimulated by bivalent cations in freeze/thawed granule preparations were: Mg2+ (100%) greater than Mn2+ (82%) greater than Ca2+ (40%) greater than Co2+ (36%) greater than Zn2+ (0%), and in intact granules were: Mg2+ (100%) greater than Mn2+ (85%) greater than Co2+ (61%) greater than Ca2+ (42%). Tributyltin and carbonyl cyanide p-trifluoromethoxyphenylhydrazone affected Mg2+-, Mn2+- and Co2+-activated, but not Ca2+-activated, ATP hydrolysis. Correspondingly, only Mg2+, Mn2+ and Co2+ supported the generation of a delta psi and delta mu H+ across granule membranes in the presence of ATP. 4. The results were consistent with a single proton translocase that had its catalytic site exposed on the external face of the granule membrane. The indicated specificity (Mg2+ATP = Mn2+ATP greater than Co2+ATP greater than Mg2+GTP greater than Mg2+ITP) was similar to that of enzymes described in membrane fractions prepared from adenohypophyseal tissue, adrenal chromaffin granules and yeast vacuoles. The insulin-granule activity thus appears to be a type of proton translocase, which is characteristic of intracellular storage vesicles in eukaryotic cells.

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Secretagogue-dependent Phosphorylation of the Insulin Granule Membrane Protein Phogrin Is Mediated by cAMP-dependent Protein Kinase

Journal of Biological Chemistry ◽

10.1074/jbc.m102580200 ◽

2001 ◽

Vol 276 (34) ◽

pp. 31919-31928 ◽

Cited By ~ 17

Author(s):

Christina Wasmeier ◽

John C. Hutton

Keyword(s):

Protein Kinase ◽

Membrane Protein ◽

Dependent Protein Kinase ◽

Camp Dependent Protein Kinase ◽

Granule Membrane ◽

Dependent Protein ◽

Insulin Granule

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Fatty acids induce amylin expression and secretion by pancreatic β-cells

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.00242.2009 ◽

2010 ◽

Vol 298 (1) ◽

pp. E99-E107 ◽

Cited By ~ 29

Author(s):

Dongfei Qi ◽

Kun Cai ◽

Oumei Wang ◽

Zongmeng Li ◽

Juan Chen ◽

...

Keyword(s):

Fatty Acids ◽

Insulin Release ◽

De Novo ◽

Secretory Granules ◽

Protein Synthesis Inhibitor ◽

Transcriptional Level ◽

Β Cells ◽

Pancreatic Β Cells ◽

Min6 Cells ◽

Insulin Expression

Amylin is the major component of pancreatic amyloid, which is implicated in the development of type 2 diabetes. It is costored with insulin in the secretory granules of pancreatic β-cells and cosecreted with insulin following stimulation with glucose. Here, we investigate the effect of fatty acids (FAs) on amylin expression and secretion by β-cells and explore the underlying mechanisms. Palmitate and oleate dose-dependently induced amylin mRNA accumulation in murine pancreatic β-cell line MIN6 and primary pancreatic islets. the inductive effect of FAs on amylin expression is independent of glucose concentration. FAs upregulated amylin expression at the transcriptional level, and FAs must be metabolized to induce amylin expression. FAs also significantly induced human amylin promoter activation. Pretreatment of MIN6 cells with Ca2+ chelator (EGTA, BAPTA-AM) PKC inhibitor Gö-6976 or protein synthesis inhibitor cycloheximide significantly inhibited FA-induced amylin mRNA expression. Transcription factors cAMP-responsive element-binding protein, pancreatic and duodenal homeobox factor-1, and peroxisome proliferator-activated receptor were not involved in FA-induced amylin expression. Palmitate and oleate both increased amylin and insulin release from MIN6 cells and stimulated amylin expression but had no effect on insulin expression. Mice refed with Intralipid had significantly higher levels of plasma FFA, amylin, and insulin than those refed with saline. These data demonstrate that FAs differently regulate amylin and insulin expression and induce both amylin and insulin release. Ca2+ and PKC signaling pathways and de novo-synthesized protein(s) were involved in FA-induced amylin expression. Induction of amylin production and release by FA may contribute to its biological functions under physiological conditions.

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