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Specific roles of G(i) protein family members revealed by dissecting SST5 coupling in human pituitary cells
- Source :
- Journal of cell science. 126(Pt 2)
- Publication Year :
- 2012
-
Abstract
- Summary Despite intensive investigation over the past 20 years, the specific role played by individual Gi protein family members in mediating complex cellular effects is still largely unclear. Therefore, we investigated the role of specific Gi proteins in mediating somatostatin (SS) effects in somatotroph cells. Because our previous data showed that SS receptor type 5 (SST5) carrying a spontaneous R240W mutation in the third intracellular loop had a similar ability to inhibit intracellular cAMP levels to the wild-type protein but failed to mediate inhibition of growth hormone (GH) release and cell proliferation, we used this model to check specific receptor–G-protein coupling by a bioluminescent resonance energy transfer analysis. In HEK293 cells, wild-type SST5 stimulated the activation of Gαi1–3 and GαoA, B, whereas R240W SST5 maintained the ability to activate Gαi1–3 and GαoB, but failed to activate the splicing variant GαoA. To investigate the role of the selective deficit in GαoA coupling, we co-transfected human adenomatous somatotrophs with SST5 and a pertussis toxin (PTX)-resistant GαoA (GαoA(PTX-r)) protein. In PTX-treated cells, GαoA(PTX-r) rescued the ability of the selective SST5 analog BIM23206 to inhibit extracellular signal-related kinase 1/2 (ERK1/2) phosphorylation, GH secretion and intracellular cAMP levels. Moreover, we demonstrated that silencing of GαoA completely abolished SST5-mediated inhibitory effects on GH secretion and ERK1/2 phosphorylation, but not on cAMP levels. In conclusion, by analysing the coupling specificity of human SST5 to individual Gαi and Gαo subunits, we identified a crucial role for GαoA signalling in human pituitary cells.
- Subjects :
- medicine.medical_specialty
G protein
Cell
Gi alpha subunit
Biology
GTP-Binding Protein alpha Subunits, Gi-Go
Pertussis toxin
Transfection
Internal medicine
medicine
Humans
Receptors, Somatostatin
Phosphorylation
education
education.field_of_study
Somatostatin receptor-5
Kinase
HEK 293 cells
Cell Biology
Growth hormone secretion
Cell biology
Coupling (electronics)
Endocrinology
medicine.anatomical_structure
HEK293 Cells
Pituitary Gland
Signal transduction
Growth Hormone-Secreting Pituitary Adenoma
Signal Transduction
Subjects
Details
- ISSN :
- 14779137
- Volume :
- 126
- Issue :
- Pt 2
- Database :
- OpenAIRE
- Journal :
- Journal of cell science
- Accession number :
- edsair.doi.dedup.....fe4594426536b71eba47cf88d69b84ed