Cell-specific localization of G protein alpha-subunits in the islets of Langerhans

G protein alpha-subunits are involved in the transduction of receptor-media ted regulation of insulin and glucagon secretions. To get further insight i nto the status of G proteins in alpha and beta-cells of the Langerhans isle ts, we have used immunohistochemistry to study the distribution of alpha-su bunits in pancreas sections from the rat. Our results show that only insulin-immunoreactive beta-cells display immuno reactivity for selective antibodies directed against the different members of the G(alpha s) and G(alpha 12)-families (alpha(s), alpha(olf), and alpha (12), alpha(13) respectively). Immunoreactivities for antibodies directed a gainst members of the G(alpha q)- and G(alpha i)-families showed a more div erse localization: alpha(11) and alpha(o2) were only detected in glucagon-i mmunoreactive alpha-cells, whereas alpha(i1) was detected in all beta-cells but only in a few alpha-cells. Even though beta-cells showed immunoreactiv ities for alpha(o)-non-isoform-selective antibodies, we could not identify the isoform(s) present using selective alpha(o1) and alpha(o2) antibodies. Other members of the G(alpha q)- and G(alpha i)-families (alpha(i3,) alpha( t2) , alpha(z), and alpha(q)) were detected in both alpha- and beta- cells. In conclusion, our findings demonstrate a clear difference in the localizat ion of G protein alpha-subunits between alpha- and beta-cells, suggesting t he involvement of specific receptor transduction pathways for the neuronal/ hormonal regulation of alpha- and beta-cell functions.