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Downregulation of platelet-derived growth factor receptor-beta in Shp-2 mutant fibroblast cell lines
1Department of Biochemistry and Molecular Biology, and Walther Oncology Center, Indiana University School of Medicine, Indianapolis 46202-5121, USA.
Abstract:
The SH2-containing tyrosine phosphatase Shp-2 appears to function downstream of a variety of growth factor receptors and might play a positive role in cell proliferation. Here we report that expression of the beta subunit of platelet-derived growth factor receptor (PDGFR-beta) was specifically downregulated in mutant fibroblasts lacking a functional Shp-2, while the levels of PDGFR-alpha EGFR and IGFIR were not changed. PDGF-stimulated DNA synthesis and extracellular signal regulated kinase (Erk) activation was severely suppressed in mutant cells. RasGAP, that responds to activation of PDGFR-beta but not PDGFR-alpha, was not phosphorylated on tyrosine in mutant cells upon PDGF-treatment. Northern blot analysis failed to detect PDGFR-beta mRNA in mutant cells. The transcription initiation from the PDGFR-beta gene promoter was not significantly changed, but the half-life of its mRNA was shortened in Shp-2 mutant cells. These observations indicate that Shp-2 not only participates in transmission of signals from growth factor receptors but also plays a specific role in the control of the PDGFR-beta expression. We propose that this is an important mechanism for the positive control of cell proliferation by Shp-2.
Insights
The phosphatase Shp-2 is crucial for platelet-derived growth factor receptor beta (PDGFR-beta) expression and cell proliferation. Shp-2 regulates PDGFR-beta mRNA stability, impacting cell growth signals.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Shp-2 (SH2-containing tyrosine phosphatase) is implicated in signaling pathways downstream of growth factor receptors.
- Its role in cell proliferation suggests involvement in regulating receptor expression or signaling.
Purpose of the Study:
- To investigate the specific role of Shp-2 in regulating platelet-derived growth factor receptor (PDGFR) signaling and expression.
- To determine if Shp-2 influences the expression of specific PDGFR subunits and subsequent cellular responses.
Main Methods:
- Analysis of PDGFR-beta expression in Shp-2 deficient fibroblasts.
- Assessment of PDGF-stimulated DNA synthesis and Erk activation.
- Investigation of RasGAP phosphorylation.
- Northern blot analysis to examine PDGFR-beta mRNA levels and stability.
- Analysis of PDGFR-beta gene promoter activity.
Main Results:
- Shp-2 deficient cells showed specifically downregulated PDGFR-beta expression, while PDGFR-alpha, EGFR, and IGFIR levels remained unchanged.
- PDGF-stimulated DNA synthesis and Erk activation were significantly suppressed in Shp-2 mutant cells.
- RasGAP phosphorylation was impaired in mutant cells upon PDGF treatment.
- PDGFR-beta mRNA levels were reduced due to a shortened mRNA half-life, not altered transcription initiation.
Conclusions:
- Shp-2 plays a critical role in controlling PDGFR-beta expression, specifically by regulating mRNA stability.
- This regulation of PDGFR-beta expression by Shp-2 is a key mechanism for positively controlling cell proliferation.