The mitogen-activated protein kinase Erk5 mediates human mesangial cell activation.
BACKGROUND
Mesangial activation occurs in many forms of renal disease that progress to renal failure. Mitogen-activated protein kinases (MAPKs) are important mediators involved in the intracellular network of interacting proteins that transduce extracellular stimuli to intracellular responses. The extracellular signal-regulated kinases 5 (Erk5) MAPK pathway has been involved in regulating several cellular responses. Thus, we examined the expression of Erk5 in human renal tissue and the function of Erk5 in cultured human mesangial cells.


METHODS
Erk5 was visualized in human renal tissue by immunohistochemistry and in mesangial cells by immunofluorescence microscopy using the anti-Erk5 C-terminus antibody. Erk5 expression and activation, and collagen I expression were determined by western blot. To generate a dominant-negative form of the Erk5 in human mesangial cells, an EcoRI fragment from wild-type pCEFL-HA-Erk5 was subcloned into the EcoRI site of pCDNA3. Cell proliferation was analysed by an MTT-based assay. Cell contraction was analysed by studying the changes in the planar cell surface area.


RESULTS
Erk5 was expressed in the kidney, mainly localized at the glomerular mesangium. In cultured human mesangial cells, Erk5 was activated by foetal calf serum (FCS), high glucose, endothelin-1, platelet-activating factor (PAF), epidermal growth factor (EGF) and transforming growth factor beta-1 (TGF-beta1). The expression of a dominant-negative form of Erk5 in human mesangial cells resulted in a significant decrease in proliferation, EGF-induced cell contraction and TGF-beta1-induced collagen I expression.


CONCLUSIONS
These results suggest that Erk5 is involved in agonist-induced mesangial cell contraction, proliferation and ECM accumulation and point to a multifunctional role of Erk5 in the pathophysiology of glomerular mesangial cells.
Instituto Reina Sofía de Investigación Nefrológica, Departamento de Fisiología y Farmacología, Universidad de Salamanca, Salamanca, Spain.
Fernando
F
Dorado
Soraya
S
Velasco
Azucena
A
Esparís-Ogando
Miguel
M
Pericacho
Atanasio
A
Pandiella
Juan
J
Silva
José M
JM
López-Novoa
Alicia
A
Rodríguez-Barbero
D049109:Cell Proliferation; D002478:Cells, Cultured; D024042:Collagen Type I / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000494:pharmacology; D005109:Extracellular Matrix / Q000378:metabolism; D006801:Humans; D048671:MAP Kinase Kinase 5 / Q000378:metabolism*; D050527:Mesangial Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology
D024042:Collagen Type I; D053773:Transforming Growth Factor beta1; D004815:Epidermal Growth Factor; D048671:MAP Kinase Kinase 5