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GRK2 desensitizes flow-induced responses in osteoblasts.
1Beijing Key Laboratory of Rehabilitation Technical Aids for Old-Age Disability, National Research Center for Rehabilitation Technical Aids, Beijing, China Department of Orthopaedics and Rehabilitation, The Pennsylvania State University College of Medicine, Hershey, PA, USA xingyanghui@hotmail.com.
Genetics and Molecular Research : GMR
|January 28, 2017
Summary
Bone desensitization following mechanical loading is crucial for adaptation. This study reveals that G protein-coupled receptor kinase 2 (GRK2) plays a key role in this process by desensitizing P2Y2 receptors in osteoblasts.
Area of Science:
- Bone biology
- Cell signaling
- Mechanobiology
Background:
- Bone adaptation to mechanical loading involves desensitization, but the mechanism is unclear.
- G protein-coupled receptors (GPCRs) like P2Y and parathyroid hormone receptors are implicated in osteoblast mechanobiology.
Purpose of the Study:
- To investigate the role of G protein-coupled receptor kinase 2 (GRK2) in osteoblast desensitization after mechanical stimulation.
- To elucidate the mechanism by which GRK2 influences osteoblast responses to mechanical cues.
Main Methods:
- Assessed osteoblast desensitization using cytosol Ca2+ and phosphorylated ERK1/2 activity.
- Utilized GRK2 overexpression and siRNA knockdown in MC3T3-E1 cells.
- Measured cyclooxygenase-2 mRNA expression and alkaline phosphatase activity.
- Investigated GRK2 translocation to the cell membrane.
Main Results:
- Osteoblast desensitization confirmed via Ca2+ and ERK1/2 signaling changes.
- GRK2 overexpression inhibited flow-induced ERK1/2 phosphorylation; GRK2 knockdown enhanced it.
- GRK2 overexpression reduced cyclooxygenase-2 mRNA and alkaline phosphatase activity.
- GRK2 translocated to the cell membrane post-stimulation, a prerequisite for GPCR desensitization.
Conclusions:
- GRK2 is involved in osteoblast desensitization to mechanical stimulation.
- GRK2 likely inhibits mechanical responses by desensitizing P2Y2 receptors, independent of ATP release.
- GRK2 is a key regulator of osteoblast mechanotransduction.
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