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Apelin (65-77) activates extracellular signal-regulated kinases via a PTX-sensitive G protein
Bernard Masri1, Hicham Lahlou, Honoré Mazarguil
1Unité INSERM U-397, CHU Rangueil, Bât. L3, 1 avenue Jean-Poulhès, 31403-Toulouse, France.
Abstract:
We report here that apelin (65-77) induces activation of extracellular-regulated kinases (ERKs) in Chinese hamster ovary (CHO) cells expressing the msr/apj receptor. This concentration-dependent activation was transient, peaking at 5 min. Pretreatment of CHO cells with pertussis toxin fully abrogated ERK phosphorylation, whereas overexpression of the beta-adrenergic receptor kinase-1 C-terminal fragment did not alter ERK activation. Transfection with a dominant-negative mutant of Ras was without effect on ERK activation, whereas an inhibitor of many protein kinase C isoforms, GF109203X, strongly decreased it. These results demonstrate that stimulation of the murine msr/apj receptor promotes ERK activation via the alpha subunit of a pertussis toxin-sensitive protein in a Ras-independent pathway.
Insights
Apelin (65-77) activates extracellular-regulated kinases (ERKs) in cells with the msr/apj receptor. This signaling pathway is pertussis toxin-sensitive and Ras-independent, involving protein kinase C.
Area of Science:
- Cellular signaling pathways
- Receptor-mediated signal transduction
- Molecular biology
Background:
- The apelin receptor (msr/apj) is a G protein-coupled receptor involved in various physiological processes.
- Extracellular-regulated kinases (ERKs) are key components of intracellular signaling cascades regulating cell growth and differentiation.
- Understanding the downstream signaling of apelin receptor activation is crucial for elucidating its biological functions.
Purpose of the Study:
- To investigate the signaling pathway by which apelin (65-77) activates extracellular-regulated kinases (ERKs) in Chinese hamster ovary (CHO) cells expressing the msr/apj receptor.
- To identify the specific molecular players involved in this activation process.
Main Methods:
- Utilized Chinese hamster ovary (CHO) cells stably expressing the murine msr/apj receptor.
- Administered apelin (65-77) and assessed ERK phosphorylation.
- Employed pertussis toxin pretreatment to investigate G protein involvement.
- Examined the role of beta-adrenergic receptor kinase-1 (beta-ARK1) using a dominant-negative C-terminal fragment.
- Assessed Ras pathway involvement via transfection with a dominant-negative Ras mutant.
- Inhibited protein kinase C (PKC) isoforms using GF109203X to evaluate its contribution.
Main Results:
- Apelin (65-77) induced a transient, concentration-dependent activation of ERK phosphorylation, peaking at 5 minutes.
- Pertussis toxin completely blocked ERK activation, indicating the involvement of a pertussis toxin-sensitive G protein alpha subunit.
- Overexpression of beta-ARK1 C-terminal fragment did not affect ERK activation.
- Dominant-negative Ras mutant had no impact on ERK activation, suggesting a Ras-independent pathway.
- GF109203X significantly reduced ERK activation, implicating protein kinase C isoforms.
Conclusions:
- Apelin (65-77) stimulation of the msr/apj receptor activates ERK through a pertussis toxin-sensitive G protein alpha subunit.
- The observed ERK activation is independent of Ras signaling.
- Protein kinase C isoforms play a significant role in mediating apelin-induced ERK activation via the msr/apj receptor.