Screening of Peptides that Specifically Binds to M3-M4 Extracellular Domain of Sodium Pump α1 Subunit and Analysis of Their Bioactivity In Vitro and In Vivo

Interaction between ouabain (OUA) and Na⁺/K⁺-pump remains in the current focus of hypertension research. This study aimed to find an oligopeptide that would antagonize the inhibitory effect of endogenous OUA on Na⁺/K⁺-pump and examine its activity at the cellular and organism levels. To this end, Phage Random 12 Peptide Library was employed to screen for specific polypeptide ligands that interact with M3-M4 extracellular domain of Na⁺/K⁺-pump α1 subunit known as OUA-binding site. Synthetic sequence ILEYTWLEAGGGS of extracellular domain M3-M4 of Na⁺/K⁺-pump α1 subunit was used as the target. The phage positive clones were screened and identified using the phage library and double sandwich ELISA. DNA was extracted and sequenced to synthesize 3 peptide ligands to Na⁺/K⁺-pump: P-A, P-B, and P-C. We also studied the effects of the short peptide with the highest potency for countering OUA on proliferation and apoptosis of EA.hy926 vascular endothelial cells and on systolic BP in spontaneously hypertensive rats (SHR). The effect of peptide P-A on proliferation (stimulation with physiological concentrations of OUA) and on apoptosis (stimulation with OUA in high concentrations) of EA.hy926 vascular endothelial cells was assessed by the MTT test and flow cytometry, respectively. In SHR rats, intravenous injection of P-A decreased systolic BP. Oligopeptide P-A competitively antagonized the inhibitory action of OUA on Na⁺/K⁺-pump, OUA-induced proliferation, and OUA-provoked apoptosis of cultured EA.hy926 cells. Our findings open vista for the emergence of novel hypertensive drugs.