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Effect of platelet-derived growth factor isoforms in rat metanephric mesenchymal cells
Jill M Ricono1, Mazen Arar, Goutam Ghosh Choudhury
1Department of Medicine, University of Texas Health Science Center, San Antonio, Texas 78229-3900, USA.
Abstract:
Platelet-derived growth factor (PDGF) B-chain or PDGF beta-receptor-deficient mice lack mesangial cells. To explore potential mechanisms for failure of PDGF A-chain to rescue mesangial cell phenotype, we investigated the biological effects and signaling pathways of PDGF AA and PDGF BB in metanephric mesenchymal (MM) cells isolated from rat kidney. PDGF AA caused modest cell migration but had no effect on DNA synthesis, unlike PDGF BB, which potently stimulated migration and DNA synthesis. PDGF AA and PDGF BB significantly increased the activities of phosphatidylinositol 3-kinase (PI 3-K) and mitogen-activated protein kinase (MAPK). PDGF BB was more potent than PDGF AA in activating PI 3-K or MAPK in these cells. Pretreatment of MM cells with the MAPK kinase (MEK) inhibitor PD-098059 abrogated PDGF BB-induced DNA synthesis, whereas the PI 3-K inhibitor wortmannin had a very modest inhibitory effect on DNA synthesis (approximately Delta20%). On the other hand, wortmannin completely blocked PDGF AA- and PDGF BB-induced migration, whereas PD-098059 had a modest inhibitory effect on cell migration. These data demonstrate that activation of MAPK is necessary for the mitogenic effect of PDGF BB, whereas PI 3-K is required for the chemotactic effect of PDGF AA and PDGF BB. Although PDGF AA stimulates PI 3-K and MAPK activity, it is not mitogenic and only modestly chemotactic. Collectively, the data may have implications related to the failure of PDGF AA to rescue mesangial cell phenotype in PDGF B-chain or PDGF-beta-receptor deficiency.
Insights
Platelet-derived growth factor (PDGF) AA only modestly promotes cell migration via PI 3-K, while PDGF BB drives both migration and DNA synthesis through MAPK and PI 3-K pathways, explaining PDGF AA
Area of Science:
- Nephrology
- Cell Biology
- Molecular Biology
Background:
- Mesangial cells are crucial for kidney function and are absent in PDGF B-chain or PDGF beta-receptor deficient mice.
- Understanding the roles of different PDGF isoforms (AA and BB) is key to addressing mesangial cell development.
- Investigating PDGF signaling pathways in metanephric mesenchymal cells provides insight into kidney development.
Purpose of the Study:
- To investigate the biological effects and signaling pathways of PDGF AA and PDGF BB in rat metanephric mesenchymal (MM) cells.
- To determine the specific roles of phosphatidylinositol 3-kinase (PI 3-K) and mitogen-activated protein kinase (MAPK) in PDGF-mediated MM cell responses.
- To elucidate why PDGF AA may fail to rescue mesangial cell phenotype in certain genetic deficiencies.
Main Methods:
- Isolation and culture of rat metanephric mesenchymal (MM) cells.
- Stimulation of MM cells with PDGF AA and PDGF BB.
- Assessment of cell migration and DNA synthesis.
- Measurement of PI 3-K and MAPK pathway activation using specific inhibitors (PD-098059 for MEK, wortmannin for PI 3-K).
Main Results:
- PDGF BB potently stimulated both MM cell migration and DNA synthesis.
- PDGF AA weakly stimulated migration but had no effect on DNA synthesis.
- Both PDGF AA and PDGF BB activated PI 3-K and MAPK, with PDGF BB being more potent.
- MAPK activation was essential for PDGF BB-induced DNA synthesis.
- PI 3-K activation was required for PDGF AA- and PDGF BB-induced cell migration.
Conclusions:
- PDGF BB's mitogenic effect relies on MAPK activation, while its chemotactic effect involves PI 3-K.
- PDGF AA's chemotactic effect is PI 3-K dependent, but it lacks significant mitogenic potential.
- These distinct signaling pathway utilizations explain PDGF AA's limited efficacy in rescuing mesangial cell function in PDGF deficiency models.