Angiotensin II Stimulates Protein Phosphatase 2A Activity in Cultured Neuronal Cells Via Type 2 Receptors in a Pertussis Toxin Sensitive Fashion

Recent studies have suggested a role for an inhibitory G protein (Gi) and protein Phosphatase 2A (PP2A) in the angiotensin II (Ang II) type 2 (AT2) receptor mediated stimulation of neuronal K+ currents. In the present study we have directly analyzed the effects of Ang II on PP2A activity in neurons cultured from newborn rat hypothalamus and brainstem. Ang II elicited time (30 min - 24 h)- and concentration (10 nM -1 μM)-dependent increases in PP2A activity in these cells. This effect of Ang II involved AT2 receptors, since it was inhibited by the AT2 receptor selective ligand PD123319 (1 μM), but not by the Ang II type 1 receptor antagonist losartan (1 μM). Furthermore, the stimulatory effects of Ang II on PP2A activity were inhibited by pretreatment of cultures with pertussis toxin (PTX) (200 ng/ml; 24 h) indicating the involvement of an inhibitory G-protein; and by cycloheximide (CHX) (1 μg/ml; 30 min) indicating a requirement for protein synthesis. These effects of Ang II appear to be via activation of PP2A, since Western Blot analyses revealed no effects of this peptide on the protein levels of the catalytic subunit of PP2A in cultured neurons. In summary, these data suggest that PP2A is a key component of the intracellular pathways coupled to neuronal AT2 receptors.