title: Islet Endothelial Cells Induce Glycosylation and Increase Cell-surface Expression of Integrin β1 in β Cells.
abstract: The co-culturing of insulinoma and islet-derived endothelial cell (iEC) lines results in the spontaneous formation of free-floating pseudoislets (PIs). We previously showed that iEC-induced PIs display improved insulin expression and secretion in response to glucose stimulation. This improvement was associated with a de novo deposition of extracellular matrix (ECM) proteins by iECs in and around the PIs. Here, iEC-induced PIs were used to study the expression and posttranslational modification of the ECM receptor integrin β1. A wide array of integrin β subunits was detected in βTC3 and NIT-1 insulinomas as well as in primary islets, with integrin β1 mRNA and protein detected in all three cell types. Interestingly, the formation of iEC-induced PIs altered the glycosylation patterns of integrin β1, resulting in a higher molecular weight form of the receptor. This form was found in native pancreas but was completely absent in monolayer β-cells. Fluorescence-activated cell sorting analysis of monolayers and PIs revealed a higher expression of integrin β1 in PIs. Antibody-mediated blocking of integrin β1 led to alterations in β-cell morphology, reduced insulin gene expression, and enhanced glucose secretion under baseline conditions. These results suggest that iEC-induced PI formation may alter integrin β1 expression and posttranslational modification by enhancing glycosylation, thereby providing a more physiological culture system for studying integrin-ECM interactions in β cells.
authors.affiliation: From the Research Institute, Islet Biology, Winthrop-University Hospital, Mineola, New York 11501 and.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Spelios
authors.affiliation: From the Research Institute, Islet Biology, Winthrop-University Hospital, Mineola, New York 11501 and.
authors.forename: John A
authors.initials: JA
authors.lastname: Olsen
authors.affiliation: From the Research Institute, Islet Biology, Winthrop-University Hospital, Mineola, New York 11501 and.
authors.forename: Lauren A
authors.initials: LA
authors.lastname: Kenna
authors.affiliation: From the Research Institute, Islet Biology, Winthrop-University Hospital, Mineola, New York 11501 and Stony Brook University School of Medicine, Stony Brook, New York 11794 eakirav@winthrop.org.
authors.forename: Eitan M
authors.initials: EM
authors.lastname: Akirav
mesh_terms: D000818:Animals; D001483:Base Sequence; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000378:metabolism; D017931:DNA Primers; D004727:Endothelium / Q000166:cytology / Q000378:metabolism; D006031:Glycosylation; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism*; D007515:Islets of Langerhans / Q000166:cytology* / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D017931:DNA Primers; D019012:Integrin beta1
keywords: beta cell (B-cell); diabetes; extracellular matrix; glucose-stimulated insulin secretion; insulin; insulinoma; integrin; islet endothelial cells; pancreatic islet; pseudoislet