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.
Guettier
Jean-Marc
JM
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
Gautam
Dinesh
D
Scarselli
Marco
M
Ruiz de Azua
Inigo
I
Li
Jian Hua
JH
Rosemond
Erica
E
Ma
Xiaochao
X
Gonzalez
Frank J
FJ
Armbruster
Blaine N
BN
Lu
Huiyan
H
Roth
Bryan L
BL
Wess
Jürgen
J
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