Angiotensin II-induced nuclear targeting of the angiotensin type 1 (AT1) receptor in brain neurons

Angiotensin II (Ang II) interaction with the neuronal AT(1) receptor results in a chronic stimulation of neuromodulation that involves the expression of norepinephrine transporter (NET) and tyrosine hydroxylase (TH). In view of this unique property and the presence of putative nuclear localization signal (NLS) consensus sequence in the AT(1) receptor, this study was conducted to investigate the hypothesis that Ang II would induce nuclear sequestration of this G protein-coupled receptor and that the sequestration may have implications on Ang II-induced expression of NET and TH genes. Incubation of neuronal cultures with Ang Il caused a time-and dose-dependent increase in the levels of AT(1) receptor immunoreactivity in the nucleus. A 6.7-fold increase was observed with 100 nM Ang II, in 15 min, that was blocked by losartan, an AT(1) receptor-specific antagonist. Ang II-induced nuclear sequestration was specific for AT(1) receptor, because Ang II failed to produce a similar effect on neuronal AT(1) receptors. The presence of the putative NLS sequence in the cytoplasmic tail of the AT(1) receptor seems to be the key in nuclear targeting because: 1) nuclear targeting was attenuated by a peptide of the AT(1) receptor that contained the putative NLS sequence; and 2) Ang II failed to cause nuclear translocation of the AT(2) receptor, which does not contain the putative NLS. Ang II also caused a time- and dose-dependent stimulation of P62 phosphorylation, a glycoprotein of the nuclear pore complex. A 6-fold stimulation of phosphorylation was observed with 100 nM Ang II, in 15 min, that was completely blocked by losartan and not by PD123,319, an AT(2) receptor specific antagonist. Preloading of neurons with p62-pep (a peptide containing consenses of mitogen-activated protein kinase in p62) resulted in a loss of Ang II-induced p62 phosphorylation and stimulation of NET and TH messenger RNA levels. In conclusion, these data demonstrate that Ang II induces nuclear sequestration of AT(1) receptor involving NLS in the AT(1) receptor and p62 of the nuclear pore complex in brain neurons. A possible role of such a nuclear targeting of the AT(1) receptor on chronic neuromodulatory actions of Ang II has been discussed.