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Functional cross-talk between angiotensin II and epidermal growth factor receptors in NIH3T3 fibroblasts
Paola De Paolis1, Antonio Porcellini, Carmine Savoia
1IRCSS Istituto Neurologico Mediterraneo Neuromed, Via Atinense 18, Località Camerelle, Pozzilli (Is), Italy.
Background:
The main angiotensin (Ang) II subtype receptors (AT1R and AT2R) are involved in cellular growth processes and exert functionally antagonistic effects.
Objective:
To characterize the mechanisms by which Ang II receptors influence growth, by investigating the interactions between Ang II subtype receptors and epidermal growth factor (EGF) receptors on mitogen-activated protein kinase (MAPK) pathway activation.
Design And Methods:
The experiments were performed using a mouse fibroblast cell line, NIH3T3, by transient co-transfection with rat AT1R or AT2R expression vectors, or both. Extracellular-signal-regulated kinase (ERK)1/2 phosphorylation was analysed by western blot and the ERK activity was evaluated using PathDetect, an in-vivo signal transduction pathway trans-reporting system. Selective Ang II receptor antagonists (losartan for AT1R and PD123319 for AT2R) were used to investigate the contributions of each receptor to the response observed.
Results:
Our data show that, in this cellular model, both Ang II receptors phosphorylate ERK1/2. However, in the cells expressing AT1R, the EGF-induced MAPK pathway was enhanced in the presence of Ang II in a synergistic fashion. In contrast, a reduction of EGF-induced MAPK activation was observed in the cells expressing AT2R. In cells expressing both Ang II subtype receptors, Ang II promoted an enhancement of EGF-induced MAPK activation. However, in the presence of the AT1R antagonist, losartan, the effect of EGF was reduced.
Conclusion:
These data indicate the existence of an opposite cross-talk of AT1R and AT2R with EGF receptors, and suggest a complex functional interaction between these pathways in the regulation of cellular growth processes.