A2B5-reactive ganglioside expression is an index of differentiation in rat insulinoma (RIN) cells

To investigate the relationship between surface ganglioside expression and pancreatic islet cell differentiation, we examined the function of five rat insulinoma (RIN-m5F) sublines A4, A6, A7, A10, and A12 selected for increased expression of A2B5-reactive gangliosides, as well as a subline AlGh, low in A2B5- but high in 3G5-reactive ganglioside expression. Class I major histocompatibility (MHC) protein expression was also measured in the sublines because of our previous finding that class I proteins were preferentially expressed on human insulinoma tissue compared with differentiated islet cells. In comparison with parental RIN-m5F cells, subline A12 displayed a 7.6-fold increase in A2B5 expression and a 3.4-fold increase in the number of A2B5 positive cells (81% vs. 24%). A2B5 expression was increased 1.3-, 5.4-, 5.4-, and 6.9-fold on A4, A6, A7, and A10 sublines, respectively. In contrast, AlGh cells, which had comparable A2B5 expression to parental cells, displayed a 2.9-fold increase in 3G5 expression and an 8-fold increase in the number of 3G5 positive cells (72% vs. 9%). Insulin secretion and content increased with increasing A2B5 expression. On day 2, secretion was 1.2-, 8-, 8-, 21-, and 18-fold higher and content 1.4-, 4-, 5-, 26-, and 33-fold higher for A4, A6, A7, A10, and A12 cells, respectively, compared to parental cells. There was a direct association between expression of A2B5 and the level of insulin messenger RNA (mRNA) in the sublines. Neither glucagon nor somatostatin was detected in any subline. The AlGh subline secreted and contained less insulin than parental cells. Fully differentiated adult rat islet cells, the majority of which are beta-cells, contained a lower number of 3G5 (12%) than A2B5 (57%) positive cells. Compared to parental cells, class I MHC proteins were decreased 4-fold on A12 cells, but increased 1.5-fold on AlGh cells. We conclude that, at least in RIN cells, the expression of A2B5-reactive ganglioside expression is associated directly, and class I MHC protein expression indirectly, with beta-cell differentiation.