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Published on: May 13, 2014
Erk is essential for growth, differentiation, integrin expression, and cell function in human osteoblastic cells
C F Lai1, L Chaudhary, A Fausto
1Division of Bone and Mineral Diseases, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
Abstract:
Extracellular signal-regulated kinases (Erks), members of the mitogen-activated protein kinase superfamily, play an important role in cell proliferation and differentiation. In this study we employed a dominant negative approach to determine the role of Erks in the regulation of human osteoblastic cell function. Human osteoblastic cells were transduced with a pseudotyped retrovirus encoding either a mutated Erk1 protein with a dominant negative action against both Erk1 and Erk2 (Erk1DN cells) or the LacZ protein (LacZ cells) as a control. Both basal and growth factor-stimulated MAPK activity and cell proliferation were inhibited in Erk1DN cells. Expression of Erk1DN protein suppressed both osteoblast differentiation and matrix mineralization by decreasing alkaline phosphatase activity and the deposition of bone matrix proteins. Cell adhesion to collagen, osteopontin, and vitronectin was decreased in Erk1DN cells as compared with LacZ cells. Cell spreading and migration on these matrices were also inhibited. In Erk1DN cells, expression of alphabeta(1), alpha(v)beta(3), and alpha(v)beta(5) integrins on the surface was decreased. Metabolic labeling indicated that the synthesis of these integrins was inhibited in Erk1DN cells. These data suggest that Erks are not only essential for the growth and differentiation of osteoblasts but also are important for osteoblast adhesion, spreading, migration, and integrin expression.
Insights
Extracellular signal-regulated kinases (Erks) are crucial for human osteoblast growth, differentiation, and function. Inhibiting Erks impairs osteoblast mineralization, adhesion, and migration by affecting integrin expression and synthesis.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Extracellular signal-regulated kinases (Erks) are key components of the mitogen-activated protein kinase (MAPK) signaling pathway.
- Erks are known to regulate fundamental cellular processes such as proliferation and differentiation.
Purpose of the Study:
- To investigate the specific role of Erks in regulating human osteoblastic cell function using a dominant-negative approach.
- To elucidate the impact of Erk inhibition on osteoblast differentiation, matrix production, and cell behavior.
Main Methods:
- Human osteoblastic cells were genetically modified using a retroviral vector to express a dominant-negative Erk1 (Erk1DN) or a control LacZ protein.
- Assessed MAPK activity, cell proliferation, alkaline phosphatase activity, matrix mineralization, cell adhesion, spreading, migration, and integrin expression.
Main Results:
- Erk1DN cells exhibited inhibited basal and growth factor-stimulated MAPK activity and proliferation.
- Osteoblast differentiation, matrix mineralization, and alkaline phosphatase activity were significantly suppressed in Erk1DN cells.
- Cell adhesion, spreading, and migration on collagen, osteopontin, and vitronectin were reduced, correlating with decreased expression and synthesis of key integrins (alphabeta(1), alpha(v)beta(3), alpha(v)beta(5)).
Conclusions:
- Erks are essential regulators of human osteoblast growth and differentiation.
- Erk signaling pathways are critical for maintaining osteoblast adhesion, migration, and integrin expression, impacting bone matrix formation.
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