Differential expression of E-cadherin at the surface of rat β-cells as a marker of functional heterogeneity

The aim of this study was to assess whether the expression of E-cadherin at the surface of rat beta-cells is regulated by insulin secretagogues and correlates with insulin secretion. When cultured under standard conditions, virtually all beta-cells expressed E-cadherin observed by imtriunofluorescence, but heterogeneous staining was observed. Using fluorescence-activated cell sorting (FACS), two beta-cell sub-populations were sorted: one that was poorly labeled ('ECad-low') and another that was highly labeled ('ECad-high'). After 1-h stimulation with 16-7 mM glucose, insulin secretion (reverse hemolytic plaque assay) from individual ECad-high beta-cells was higher than that from ECad-low P-cells. Ca2+-dependent beta-cell aggregation was increased at 16-7 mM glucose when compared with 2-8 mM glucose. E-cadherin at the surface of beta-cells was increased after 18h at 11 center dot 1 and 22 center dot 2mM glucose when compared with 2-8 mM glucose, with the greatest increase at 22 center dot 2 mM glucose+ 0-5 mM isobutylmethylxanthine (IBMX). While no labeling was detected on freshly trypsinized cells, the proportion of stained cells increased in a time-dependent manner during culture for 1, 3, and 24 It. This recovery was faster when cells were incubated at 16-7 vs 2-8 mM glucose. Cycloheximide inhibited expression of E-cadherin at 2-8 mM glucose, but not at 16-7 mM,while depolymerization of actin by either cytochasin B or latrunculin B increased surface Ecadherin at low glucose. In conclusion, these results show that expression of E-cadherin at the surface of islet beta-cells is controlled by secretagogues including glucose, correlates with insulin secretion, and can serve as a surface marker of beta-cell function.