FoxA2 and RNA Pol II Mediate Human Islet Amyloid Polypeptide Turnover in ER-stressed Pancreatic β-cells

Here, we investigated transcriptional and trafficking mechanisms of human islet amyloid polypeptide (hIAPP) in normal and stressed β-cells. In high glucose-challenged human islets and rat insulinoma cells overexpressing hIAPP, cell fractionation studies revealed increased accumulation of hIAPP. Unexpectedly, a significant fraction (up to 22%) of hIAPP was found in the nuclear soluble and chromatin-enriched fractions of cultured human islet and rat insulinoma cells. The nucleolar accumulation of monomeric forms of hIAPP did not have any adverse effect on the proliferation of β-cells nor did it affect nucleolar organization or function. However, intact nucleolar organization and function were essential for hIAPP expression under normal and ER-stress conditions as RNA polymerase II inhibitor, α-amanitin, reduced hIAPP protein expression evoked by high glucose and thapsigargin. Promoter activity studies revealed the essential role of transcription factor FoxA2 in hIAPP promoter activation in ER-stressed β-cells. Transcriptome and secretory studies demonstrate that the biosynthetic and secretory capacity of islet β-cells was preserved during ER stress. Thus, the main reason for increased intracellular hIAPP accumulation is its enhanced biosynthesis under these adverse conditions.

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Graphene quantum dots rescue protein dysregulation of pancreatic β-cells exposed to human islet amyloid polypeptide

Nano Research ◽

10.1007/s12274-019-2520-7 ◽

2019 ◽

Vol 12 (11) ◽

pp. 2827-2834 ◽

Cited By ~ 6

Author(s):

Ava Faridi ◽

Yunxiang Sun ◽

Monika Mortimer ◽

Ritchlynn R. Aranha ◽

Aparna Nandakumar ◽

...

Keyword(s):

Quantum Dots ◽

Islet Amyloid Polypeptide ◽

Graphene Quantum Dots ◽

Human Islet ◽

Β Cells ◽

Pancreatic Β Cells ◽

Islet Amyloid ◽

Human Islet Amyloid Polypeptide

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Lipid Modulation in the Formation of β-Sheet Structures. Implications for De Novo Design of Human Islet Amyloid Polypeptide and the Impact on β-Cell Homeostasis

Biomolecules ◽

10.3390/biom10091201 ◽

2020 ◽

Vol 10 (9) ◽

pp. 1201 ◽

Cited By ~ 1

Author(s):

Israel Martínez-Navarro ◽

Raúl Díaz-Molina ◽

Angel Pulido-Capiz ◽

Jaime Mas-Oliva ◽

Ismael Luna-Reyes ◽

...

Keyword(s):

Insulin Secretion ◽

Membrane Lipids ◽

Islet Amyloid Polypeptide ◽

Human Islet ◽

Β Cells ◽

Islet Amyloid ◽

Human Islet Amyloid Polypeptide ◽

Insulin Granules ◽

The Impact ◽

Β Sheet

Human islet amyloid polypeptide (hIAPP) corresponds to a 37-residue hormone present in insulin granules that maintains a high propensity to form β-sheet structures during co-secretion with insulin. Previously, employing a biomimetic approach, we proposed a panel of optimized IAPP sequences with only one residue substitution that shows the capability to reduce amyloidogenesis. Taking into account that specific membrane lipids have been considered as a key factor in the induction of cytotoxicity, in this study, following the same design strategy, we characterize the effect of a series of lipids upon several polypeptide domains that show the highest aggregation propensity. The characterization of the C-native segment of hIAPP (residues F23-Y37), together with novel variants F23R and I26A allowed us to demonstrate an effect upon the formation of β-sheet structures. Our results suggest that zwitterionic phospholipids promote adsorption of the C-native segments at the lipid-interface and β-sheet formation with the exception of the F23R variant. Moreover, the presence of cholesterol did not modify this behavior, and the β-sheet structural transitions were not registered when the N-terminal domain of hIAPP (K1-S20) was characterized. Considering that insulin granules are enriched in phosphatidylserine (PS), the property of lipid vesicles containing negatively charged lipids was also evaluated. We found that these types of lipids promote β-sheet conformational transitions in both the C-native segment and the new variants. Furthermore, these PS/peptides arrangements are internalized in Langerhans islet β-cells, localized in the endoplasmic reticulum, and trigger critical pathways such as unfolded protein response (UPR), affecting insulin secretion. Since this phenomenon was associated with the presence of cytotoxicity on Langerhans islet β-cells, it can be concluded that the anionic lipid environment and degree of solvation are critical conditions for the stability of segments with the propensity to form β-sheet structures, a situation that will eventually affect the structural characteristics and stability of IAPP within insulin granules, thus modifying the insulin secretion.

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Biologically active human islet amyloid polypeptide/amylin in transgenic mice

Acta Endocrinologica ◽

10.1530/eje.0.1360107 ◽

1997 ◽

Vol 136 (1) ◽

pp. 107-113 ◽

Cited By ~ 6

Author(s):

Karen L van Hulst ◽

Walter Born ◽

Roman Muff ◽

Cor Oosterwijk ◽

Marinus A Blankenstein ◽

...

Keyword(s):

Biological Activity ◽

Transgenic Mice ◽

Islet Amyloid Polypeptide ◽

Human Islet ◽

Cell Protein ◽

Β Cells ◽

Pancreatic Β Cells ◽

Islet Amyloid ◽

Human Islet Amyloid Polypeptide ◽

Human And Mouse

Abstract Objective: Human islet amyloid polypeptide (hIAPP), also named amylin, is a pancreatic β cell protein implicated in the pathogenesis of pancreatic islet amyloid formation and type 2 diabetes mellitus. To study the (patho)physiological roles of hIAPP, we have generated transgenic mice that overexpress hIAPP mRNA, in relation to endogenous mouse IAPP (mIAPP) mRNA, in pancreatic β cells. The biological activity of human and mouse IAPP derived from pancreatic extracts was determined. Methods: Pancreatic and plasma extracts of transgenic and control mice were analyzed by reversedphase high-performance liquid chromatography (HPLC) and radioimmunoassay, yielding a separation of hIAPP from mIAPP. Biological activity of immunoreactive human and mouse IAPP components derived from pancreatic extracts was assessed by calcitonin receptor-mediated stimulation of cyclic AMP accumulation in T47D human breast carcinoma cells. Results: The predominant immunoreactive human and mouse IAPP gene products had the retention times on HPLC analysis of the corresponding synthetic peptides. The ratio of bioactive over immunoreactive hIAPP and mIAPP was 0·93 ±0·18 and 1·19 ±0·56 respectively. In extracts of two plasma pools from 4 transgenic animals, hIAPP was 4·6- to 7-fold more abundant than mIAPP. Conclusion; This study has shown that correctly processed hIAPP produced in transgenic mouse pancreatic β cells exhibits full biological activity. The results validate these transgenic mice for the study of (patho)physiological roles of hIAPP in vivo. European Journal of Endocrinology 136 107–113

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Deletion of Caspase-8 Protects Islet β-Cells from Cytotoxic Effects of Human Islet Amyloid Polypeptide Aggregates

Canadian Journal of Diabetes ◽

10.1016/j.jcjd.2012.07.075 ◽

2012 ◽

Vol 36 (5) ◽

pp. S18

Author(s):

Yoo Jin Park ◽

Minna Woo ◽

Ziliang Ao ◽

Timothy J. Kieffer ◽

Garth L. Warnock ◽

...

Keyword(s):

Islet Amyloid Polypeptide ◽

Human Islet ◽

Caspase 8 ◽

Β Cells ◽

Islet Amyloid ◽

Cytotoxic Effects ◽

Human Islet Amyloid Polypeptide

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Fibrillation of human islet amyloid polypeptide and its toxicity to pancreatic β-cells under lipid environment

Biochimica et Biophysica Acta (BBA) - General Subjects ◽

10.1016/j.bbagen.2019.129422 ◽

2020 ◽

Vol 1864 (1) ◽

pp. 129422 ◽

Cited By ~ 5

Author(s):

Li-Ping Gao ◽

Hai-Chao Chen ◽

Ze-lin Ma ◽

An-Di Chen ◽

Hong-Li Du ◽

...

Keyword(s):

Islet Amyloid Polypeptide ◽

Human Islet ◽

Β Cells ◽

Pancreatic Β Cells ◽

Islet Amyloid ◽

Human Islet Amyloid Polypeptide ◽

Lipid Environment

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Azadirachtin inhibits amyloid formation, disaggregates pre-formed fibrils and protects pancreatic β-cells from human islet amyloid polypeptide/amylin-induced cytotoxicity

Biochemical Journal ◽

10.1042/bcj20180820 ◽

2019 ◽

Vol 476 (5) ◽

pp. 889-907 ◽

Cited By ~ 8

Author(s):

Richa Dubey ◽

Ketaki Patil ◽

Sarath C. Dantu ◽

Devika M. Sardesai ◽

Parnika Bhatia ◽

...

Keyword(s):

Pancreatic Islets ◽

Islet Amyloid Polypeptide ◽

Human Islet ◽

Dynamics Simulation ◽

Major Constituent ◽

Β Cells ◽

Pancreatic Β Cells ◽

Islet Amyloid ◽

Human Islet Amyloid Polypeptide

Abstract The human islet amyloid polypeptide (hIAPP) or amylin is the major constituent of amyloidogenic aggregates found in pancreatic islets of type 2 diabetic patients that have been associated with β-cell dysfunction and/or death associated with type 2 diabetes mellitus (T2DM). Therefore, developing and/or identifying inhibitors of hIAPP aggregation pathway and/or compound that can mediate disaggregation of preformed aggregates holds promise as a medical intervention for T2DM management. In the current study, the anti-amyloidogenic potential of Azadirachtin (AZD)—a secondary metabolite isolated from traditional medicinal plant Neem (Azadirachta indica)—was investigated by using a combination of biophysical and cellular assays. Our results indicate that AZD supplementation not only inhibits hIAPP aggregation but also disaggregates pre-existing hIAPP fibrils by forming amorphous aggregates that are non-toxic to pancreatic β-cells. Furthermore, AZD supplementation in pancreatic β-cells (INS-1E) resulted in inhibition of oxidative stress; along with restoration of the DNA damage, lipid peroxidation and the associated membrane damage, endoplasmic reticulum stress and mitochondrial membrane potential. AZD treatment also restored glucose-stimulated insulin secretion from pancreatic islets exposed to hIAPP. All-atom molecular dynamics simulation studies on full-length hIAPP pentamer with AZD suggested that AZD interacted with four possible binding sites in the amyloidogenic region of hIAPP. In summary, our results suggest AZD to be a promising candidate for combating T2DM and related amyloidogenic disorders.

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