Cell-specific localization of G protein alpha-subunits in the islets of Langerhans.
G protein alpha-subunits are involved in the transduction of receptor-mediated regulation of insulin and glucagon secretions. To get further insight into the status of G proteins in alpha- and beta-cells of the Langerhans islets, we have used immunohistochemistry to study the distribution of alpha-subunits in pancreas sections from the rat. Our results show that only insulin-immunoreactive beta-cells display immunoreactivity for selective antibodies directed against the different members of the Galphas and Galpha12-families (alphas, alphaolf, and alpha12, alpha13 respectively). Immunoreactivities for antibodies directed against members of the Galphaq- and Galphai-families showed a more diverse localization: alpha11 and alphao2 were only detected in glucagon-immunoreactive alpha-cells, whereas alphai1 was detected in all beta-cells but only in a few alpha-cells. Even though beta-cells showed immunoreactivities for alphao-non-isoform-selective antibodies, we could not identify the isoform(s) present using selective alphao1 and alphao2 antibodies. Other members of the Galphai- and Galphaq-families (alphai3, alphat2, alphaz and alphaq) were detected in both alpha- and beta-cells. In conclusion, our findings demonstrate a clear difference in the localization of G protein alpha-subunits between alpha- and beta-cells, suggesting the involvement of specific receptor transduction pathways for the neuronal/hormonal regulation of alpha- and beta-cell functions.
Unité de Recherche sur les Peptides Neurodigestifs et le Diabète, Institut National de la Santé et de la Recherche Médicale, Unité 55, 75571 Paris Cedex 12, France.
G
G
Skoglund
A
A
Basmaciogullari
B
B
Rouot
J C
JC
Marie
G
G
Rosselin
D000818:Animals; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D019204:GTP-Binding Proteins / Q000378:metabolism*; D007150:Immunohistochemistry; D007515:Islets of Langerhans / Q000378:metabolism*; D051381:Rats
D019204:GTP-Binding Proteins; D019206:GTP-Binding Protein alpha Subunits, Gi-Go