Small peptide PEP7 can decease Angiotensin II (Ang II) induced function through MAPK signaling pathway

Sequence analysis of the 5′ leader sequence (5'LS) of the rat angiotensin type 1a receptor (rAT1aR) mRNA revealed a short open reading frame (sORF) within exon 2 (E2) which is in frame with the downstream major open reading frame that encodes the AT1aR. We found that the 7 amino acid peptide (PEP7) encoded by this sORF decreased 125I‐[Sar1, Ile8]Ang II specific binding by 23% in transfected human embryonic kidney‐293 (HEK‐293) cells expressing the rAT1aR under conditions in which the scrambled PEP7 (sPEP7) did not [dpm/μg protein: Vehicle, 162.2 ± 8.2, PEP7, 125.7 ± 7.0, sPEP7, 179.9 ± 3.9; n=3]. Furthermore, PEP7 inhibited angiotensin II (Ang II)‐induced activation of extracellular signal‐regulated kinases 1 and 2 (ERK1/2) – defined as the phosphorylation of ERK1/2 (pERK1/2) with respect to total ERK1/2 (pERK/ERK) expression (measured by Western blot) in a dose‐ and time‐dependent manner. Ang II (100 nM) rapidly caused phosphorylation of ERK1/2, which was maximum after a 5 min exposure. Incubation of these cells with 2.5 μM PEP7 3 hours prior to Ang II stimulation for 5 min inhibited pERK1/2 generation by 62% [pERK1/2/ERK1/2 (AU): Ang II, 1.000 ± 0.0, Ang II+PEP7, 0.3812 ± 0.086, Ang II+sPEP7, 1.069 ± 0.18; n=2–3]. The inhibitory effect of PEP7 was not instantaneous since incubation of PEP7 20 min prior to stimulation with Ang II was without effect. Our findings suggest that PEP7 plays a regulatory role in controlling the expression and activity of the rAT1aR. [Supported by R01‐HL59502 (KS) and R01–066023 (WKS)]