A chemical-genetic approach to study G protein regulation of beta cell function in vivo.
Impaired functioning of pancreatic beta cells is a key hallmark of type 2 diabetes. beta cell function is modulated by the actions of different classes of heterotrimeric G proteins. The functional consequences of activating specific beta cell G protein signaling pathways in vivo are not well understood at present, primarily due to the fact that beta cell G protein-coupled receptors (GPCRs) are also expressed by many other tissues. To circumvent these difficulties, we developed a chemical-genetic approach that allows for the conditional and selective activation of specific beta cell G proteins in intact animals. Specifically, we created two lines of transgenic mice each of which expressed a specific designer GPCR in beta cells only. Importantly, the two designer receptors differed in their G protein-coupling properties (G(q/11) versus G(s)). They were unable to bind endogenous ligand(s), but could be efficiently activated by an otherwise pharmacologically inert compound (clozapine-N-oxide), leading to the conditional activation of either beta cell G(q/11) or G(s) G proteins. Here we report the findings that conditional and selective activation of beta cell G(q/11) signaling in vivo leads to striking increases in both first- and second-phase insulin release, greatly improved glucose tolerance in obese, insulin-resistant mice, and elevated beta cell mass, associated with pathway-specific alterations in islet gene expression levels. Selective stimulation of beta cell G(s) triggered qualitatively similar in vivo metabolic effects. Thus, this developed chemical-genetic strategy represents a powerful approach to study G protein regulation of beta cell function in vivo.
Molecular Signaling Section, Laboratory of Bioorganic Chemistry, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA. guettierj@mail.nih.gov
Jean-Marc
JM
Guettier
Dinesh
D
Gautam
Marco
M
Scarselli
Inigo
I
Ruiz de Azua
Jian Hua
JH
Li
Erica
E
Rosemond
Xiaochao
X
Ma
Frank J
FJ
Gonzalez
Blaine N
BN
Armbruster
Huiyan
H
Lu
Bryan L
BL
Roth
Jürgen
J
Wess
D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D003024:Clozapine / Q000031:analogs & derivatives / Q000494:pharmacology; D003924:Diabetes Mellitus, Type 2 / Q000378:metabolism*; D005260:Female; D019204:GTP-Binding Proteins / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D005951:Glucose Tolerance Test; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D007515:Islets of Langerhans / Q000033:anatomy & histology* / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D011869:Radioligand Assay; D043562:Receptors, G-Protein-Coupled / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*
D007328:Insulin; D043562:Receptors, G-Protein-Coupled; D019204:GTP-Binding Proteins; D003024:Clozapine; C079149:clozapine N-oxide