A role for G(z) in pancreatic islet beta-cell biology

Authors:
Kimple ME, Nixon AB, Kelly P, Bailey CL, Young KH, Fields TA and Casey PJ
In:
Source: J Biol Chem
Publication Date: (2005)
Issue: 280(36): 31708-31713
Research Area:
Gastroenterology
Cells used in publication:
INS1 832/13
Species: rat
Tissue Origin: pancreas
Platform:
Nucleofectorâ„¢ I/II/2b
Experiment
siRNA-mediated Gene Silencing: Ins-1(832/13) cells were grown to 50–75% confluence in 10-cm dishes. Cells were trypsinized, and 5 x 106 cells were electroporated with 200 pmol of annealed siRNA oligonucleotide using the Amaxa Nucleofector solution T, program T20. Each reaction was split between 4 wells of a 12-well plate. The GSIS assay was performed 48 h post nucleofection.
Abstract
Glucose-stimulated insulin secretion and beta-cell growth are important facets of pancreatic islet beta-cell biology. As a result, factors that modulate these processes are of great interest for the potential treatment of Type 2 diabetes. Here, we present evidence that the heterotrimeric G protein G(z) and its effectors, including some previously thought to be confined in expression to neuronal cells, are present in pancreatic beta-cells, the largest cellular constituent of the islets of Langerhans. Furthermore, signaling pathways upon which G alpha(z) impacts are intact in beta-cells, and G alpha(z) activation inhibits both cAMP production and glucose-stimulated insulin secretion in the Ins-1(832/13) beta-cell-derived line. Inhibition of glucose-stimulated insulin secretion by prostaglandin E (PGE1) is pertussis-toxin insensitive, indicating that other G alpha(i) family members are not involved in this process in this beta-cell line. Indeed, overexpression of a selective deactivator of G alpha(z), the RGS domain of RGSZ1, blocks the inhibitory effect of PGE1 on glucose-stimulated insulin secretion. Finally, the inhibition of glucose-stimulated insulin secretion by PGE1 is substantially blunted by small interfering RNA-mediated knockdown of G alpha(z) expression. Taken together, these data strongly imply that the endogenous E prostanoid receptor in the Ins-1(832/13) beta-cell line couples to G(z) predominantly and perhaps even exclusively. These data provide the first evidence for G(z) signaling in pancreatic beta-cells, and identify an endogenous receptor-mediated signaling process in beta-cells that is dependent on G alpha(z) function.