Related Experiment Videos
ET-1 and PDGF BB induce MEK mRNA and protein expression in mesangial cells
H Schramek1, A Sorokin, R D Watson
1Department of Medicine, Case Western Reserve University, Cleveland, Ohio, USA.
Abstract:
To evaluate a possible mechanism for the chronic regulation of MAPK/ERK kinase-1 (MEK-1) and p42 mitogen-activated protein kinase (MAPK) we studied the long-term effects of the G-protein-coupled receptor agonist endothelin-1 (ET-1) and the protein tyrosine kinase-coupled receptor agonist platelet-derived growth factor BB (PDGF BB) on MEK-1 and p42 MAPK in glomerular mesangial cells (GMCs). ET-1 and PDGF BB led to a time-dependent increase in MEK-1 mRNA expression without altering p42 MAPK mRNA levels. The effect of ET-1 and PDGF BB on MEK-1 mRNA expression was maximal after 24 h (3.3-fold) or 6 h (2.9-fold). Furthermore, the effect of ET-1 and PDGF BB on MEK-1 mRNA expression was additive (4.2-fold after 6 h) and was inhibited by actinomycin D (5 micrograms/ml). Cycloheximide (10 micrograms/ml) inhibited MEK-1 mRNA induction but stimulated p42 MAPK mRNA expression in both the absence and the presence of ET-1 and/or PDGF BB. The ET-1 and PDGF BB-induced increase in MEK-1 mRNA was accompanied by sustained enhancement of both p45 MEK protein expression after 12 h and by elevation of p42 MAPK activity for up to 24 h. We conclude that, in GMCs, MEK-1 acts like a delayed-early gene, whereas p42 MAPK resembles an immediate-early gene. MEK-1 mRNA and protein levels, as well as p42 MAPK activity, can be chronically regulated by both a seven-transmembrane domain receptor-coupled peptide such as ET-1 and by an agonist binding to a receptor with intrinsic protein tyrosine kinase activity, such as PDGF BB.
Insights
Endothelin-1 and PDGF BB chronically regulate MEK-1 and p42 MAPK in glomerular mesangial cells. MEK-1 acts as a delayed-early gene, while p42 MAPK functions as an immediate-early gene.
Area of Science:
- Cellular signaling pathways
- Molecular biology
- Renal cell biology
Background:
- Mitogen-activated protein kinases (MAPKs) are crucial in cellular responses.
- Understanding the chronic regulation of MAPK signaling is vital for cellular homeostasis.
- Glomerular mesangial cells (GMCs) play a key role in kidney function and disease.
Purpose of the Study:
- To investigate the long-term effects of endothelin-1 (ET-1) and platelet-derived growth factor BB (PDGF BB) on MEK-1 and p42 MAPK in GMCs.
- To elucidate the regulatory mechanisms of MEK-1 and p42 MAPK in response to specific agonists.
- To characterize MEK-1 and p42 MAPK as immediate- or delayed-early genes in GMCs.
Main Methods:
- Treatment of GMCs with ET-1 and PDGF BB over various time points.
- Quantitative analysis of MEK-1 and p42 MAPK mRNA and protein expression.
- Assessment of p42 MAPK activity using biochemical assays.
- Inhibition studies using actinomycin D and cycloheximide.
Main Results:
- ET-1 and PDGF BB induced a time-dependent increase in MEK-1 mRNA expression, peaking at 24h and 6h respectively.
- MEK-1 mRNA induction by ET-1 and PDGF BB was additive and sensitive to actinomycin D.
- Cycloheximide inhibited MEK-1 mRNA induction but stimulated p42 MAPK mRNA expression.
- Sustained increases in p45 MEK protein and p42 MAPK activity were observed up to 24h.
Conclusions:
- MEK-1 functions as a delayed-early gene, while p42 MAPK acts as an immediate-early gene in GMCs.
- Chronic regulation of MEK-1 and p42 MAPK is achieved through distinct receptor pathways.
- These findings provide insights into the long-term modulation of MAPK signaling in glomerular cells.