Identification of iduronate-2-sulfatase in mouse pancreatic islets

Abstract

The lysosomal enzyme iduronate-2-sulfatase (IDS) is expressed in pancreatic islets and is responsible for degradation of proteoglycans, such as perlecan and dermatan sulfate. To determine the role of IDS in islets, expression and regulation of the gene and localization of the enzyme were investigated in mouse pancreatic islets and clonal cells. The Ids gene was expressed in mouse islets and β- and α-clonal cells, in which it was localized intracellularly in lysosomes. The transcriptional expression of Ids in mouse islets increased with glucose in a dose-dependent manner (11.5, 40.2, 88, and 179% at 5.5, 11.1, 16.7, and 24.4 mM, respectively, P < 0.01 for 16.7 and 24.4 mM glucose vs. 3 mM glucose). This increase was not produced by glyceraldehyde (1 mM) or 6-deoxyglucose (21.4 mM) and was blocked by the addition of mannoheptulose (21.4 mM). Neither insulin content nor secretory response to glucose (16.7 mM) was altered in mouse islets infected with lentiviral constructs carrying the IDS gene in sense orientation. Furthermore, no decrease in islet cell viability was observed in mouse islets carrying lentiviral contracts compared with controls. However, insulin content was reduced (35% vs. controls, P < 0.001) in islets infected with IDS antisense construct, while the secretory response of those islets to glucose was maintained. Inhibition of IDS by antisense infection led to an increase in lysosomal size and a high rate of insulin granule degradation via the crinophagic route in pancreatic β-cells. We conclude that IDS is localized in lysosomes in pancreatic islet cells and expression is regulated by glucose. IDS has a potential role in the normal pathway of lysosomal degradation of secretory peptides and is likely to be essential to maintain pancreatic β-cell function.

Analyzing Microarray Data of Alzheimer's Using Cluster Analysis to Identify the Biomarker Genes

“…Identification of candidate genes could provide easily accessible biomarkers to monitor Alzheimer's, and these are SORL1, and APP, and APOE, the other 21 genes listed are related to other diseases but may also be found to be associated with Alzheimer's; these are transmembrane protein 59 [11], chaperonin containing TCP1 subunit 4 (delta) [12], insulin-like growth factor 2 receptor [13], splicing factor proline/glutamine-rich [14], peroxiredoxin 3 [15], ring finger protein 14 [16], iduronate 2-sulfatase [17], single-stranded DNA-binding protein 1 [18], spectrin repeat containing, nuclear envelope 2, thioredoxin-like 4A [19], syntaxin-binding protein 3 [20], SWI/SNF-related, matrix-associated, actin-dependent regulator of chromatin, subfamily a, member 1, unc-51-like kinase 2 ( C. elegans ), ATP/GTP-binding protein 1, fatty-acid-binding protein 7, brain [21], calbindin 1, 28 kDa [22], H2A histone family, member Y [23], coatomer protein complex, subunit alpha [12], Sin3A-associated protein, 18 kDa [24], 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase, and synaptotagmin-binding, cytoplasmic RNA-interacting protein [25]. …”

Downregulation of Sfrp5 promotes beta cell proliferation during obesity in the rat

“…), 2 mmol/l L-glutamine, 100 U/ml penicillin, and 100 μg/ml streptomycin at 37°C with 5% CO 2 . The protocol for the isolation of single islet cells has been published previously [24]. Islets were digested in PBS containing 0.125 mg/ml trypsin and 0.05 mg/ml EDTA (Gibco-BRL) at 37°C and for an additional 5 min on ice to allow islets to sediment.…”

Role of iduronate-2-sulfatase in glucose-stimulated insulin secretion by activation of exocytosis

“…This finding is significant given that the size of the ready releasable vesicle pool and part of the docked secretory granules, which are in close proximity to the plasma membrane, determine the magnitude of the initial secretory response (11). Interestingly, previous studies, although using different methodologies, and different strategies to deregulate IDS expression found IDS implication on the vesicular secretory pathway (5). The present data suggest that overexpression of hIDS increases insulin release by stimulating the late stages of exocytosis processes with no effects on more proximal events such as glucose metabolism or intracellular Ca 2ϩ levels.…”

“…Previous findings by our group demonstrated the presence of IDS in mouse pancreatic ␣-and ␤-islet cells (5), which we have now detected for the first time in human pancreatic islets. Moreover, antisense inhibition of IDS in ␤-cells resulted in degradation of insulin granules that are not directed to the secretory pool, suggesting an essential role of this enzyme in the maintenance of the pancreatic ␤-cell function (5).…”

“…Our group recently discovered that the lysosomal enzyme iduronate-2-sulfatase (IDS) is expressed in pancreatic islets and that its expression is regulated by glucose (5). IDS is an enzyme involved in the degradation of glycosaminoglycans (EC 3.1.6.13).…”