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Published on: January 7, 2013
Effects of p38MAPK isoforms on renal mesangial cell inducible nitric oxide synthase expression
Paul Lui1, Chenbo Zeng, Stephen Acton
1Department of Medicine, Renal Division, Washington University School of Medicine, Box 8126, 660 South Euclid, St Louis, MO 63110, USA.
Abstract:
Several related isoforms of p38MAPK have been identified and cloned in many species. Although they all contain the dual phosphorylation motif TGY, the expression of these isoforms is not ubiquitous. p38alpha and -beta2 are ubiquitously expressed, whereas p38gamma and -delta appear to have more restricted expression. Because there is evidence for selective activation by upstream kinases and selective preference for downstream substrates, the functions of these conserved proteins is still incompletely understood. We have demonstrated that the renal mesangial cell expresses the mRNA for all the isoforms of p38MAPK, with p38alpha mRNA expressed at the highest level, followed by p38gamma and the lowest levels of expression by p38beta2 and -delta. To determine the functional effects of these proteins on interleukin (IL)-1beta-induced inducible nitric oxide synthase (iNOS) expression, we transduced TAT-p38 chimeric proteins into renal mesangial cells and assessed the effects of wild-type and mutant p38 isoforms on ligand induced iNOS expression. We show that whereas p38gamma and -delta had minimal effects on iNOS expression, p38alpha and -beta2 significantly altered its expression. p38alpha mutant and p38beta2 wild-type dose dependently inhibited IL-1beta-induced iNOS expression. These data suggest that p38alpha and beta2 have reciprocal effects on iNOS expression in the mesangial cell, and these observations may have important consequences for the development of selective inhibitors targeting the p38MAPK family of proteins.
Insights
p38MAPK isoforms p38alpha and p38beta2 play key roles in regulating inducible nitric oxide synthase (iNOS) expression in renal mesangial cells, with reciprocal inhibitory effects. This finding is crucial for developing targeted p38MAPK inhibitors.
Area of Science:
- Cellular and Molecular Biology
- Immunology
- Renal Physiology
Background:
- p38 mitogen-activated protein kinase (MAPK) family comprises several isoforms with distinct expression patterns and functions.
- The roles of specific p38MAPK isoforms in renal mesangial cells, particularly in response to inflammatory stimuli like interleukin-1beta (IL-1beta), are not fully understood.
- Inducible nitric oxide synthase (iNOS) plays a significant role in renal inflammation and immune responses.
Purpose of the Study:
- To investigate the expression of p38MAPK isoforms in renal mesangial cells.
- To determine the functional impact of different p38MAPK isoforms on IL-1beta-induced iNOS expression.
- To elucidate the reciprocal effects of p38alpha and p38beta2 on iNOS regulation.
Main Methods:
- Quantitative analysis of p38MAPK isoform mRNA expression in renal mesangial cells.
- Transduction of renal mesangial cells with TAT-p38 chimeric proteins (wild-type and mutant isoforms).
- Assessment of IL-1beta-induced iNOS expression following p38MAPK isoform manipulation.
Main Results:
- All p38MAPK isoforms (p38alpha, -beta2, -gamma, -delta) are expressed in renal mesangial cells, with p38alpha showing the highest mRNA levels.
- p38alpha and p38beta2 isoforms significantly modulated IL-1beta-induced iNOS expression, while p38gamma and -delta had minimal effects.
- A mutant form of p38alpha and wild-type p38beta2 dose-dependently inhibited IL-1beta-induced iNOS expression.
Conclusions:
- p38alpha and p38beta2 exhibit reciprocal regulatory functions on iNOS expression in renal mesangial cells.
- These findings highlight the distinct roles of p38MAPK isoforms in inflammatory signaling within the kidney.
- The study provides a basis for developing selective p38MAPK inhibitors for renal inflammatory conditions.
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