International Journal of Molecular Sciences

Article Tetrapeptide Ac-HAEE-NH2 Protects α4β2 nAChR from Inhibition by Aβ

Evgeny P. Barykin 1, Aleksandra I. Garifulina 2,3, Anna P. Tolstova 1, Anastasia A. Anashkina 1 , Alexei A. Adzhubei 1, Yuri V. Mezentsev 4, Irina V. Shelukhina 2, Sergey A. Kozin 1, Victor I. Tsetlin 2 and Alexander A. Makarov 1,* 1 Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Vavilov St. 32, 119991 Moscow, Russia; [email protected] (E.P.B.); [email protected] (A.P.T.); [email protected] (A.A.A.); [email protected] (A.A.A.); [email protected] (S.A.K.) 2 Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Miklukho-Maklaya Street, 16/10, 117997 Moscow, Russia; [email protected] (A.I.G.); [email protected] (I.V.S.); [email protected] (V.I.T.) 3 Department of and Toxicology, University of Vienna, Althanstraße 14 (UZA II), 1090 Vienna, Austria 4 Orekhovich Institute of Biomedical Chemistry, Pogodinskaya street 10/8, 119121 Moscow, Russia; [email protected] * Correspondence: [email protected]; Tel.: +7-499-135-40-95; Fax: +7-499-135-14-05

 Received: 3 August 2020; Accepted: 27 August 2020; Published: 29 August 2020 

Abstract: The deficit in Alzheimer’s disease (AD) may arise from selective loss of cholinergic neurons caused by the binding of Aβ peptide to nicotinic receptors (nAChRs). Thus, compounds preventing such an interaction are needed to address the cholinergic dysfunction. Recent findings suggest that the 11EVHH14 site in Aβ peptide mediates its interaction with α4β2 nAChR. This site contains several charged amino acid residues, hence we hypothesized that the formation of Aβ-α4β2 nAChR complex is based on the interaction of 11EVHH14 with its charge-complementary counterpart in α4β2 nAChR. Indeed, we discovered a 35HAEE38 site in α4β2 nAChR, which is charge-complementary to 11EVHH14, and molecular modeling showed that a stable 11 14 35 38 Aβ42-α4β2 nAChR complex could be formed via the EVHH : HAEE interface. Using surface plasmon resonance and bioinformatics approaches, we further showed that a corresponding 11 14 tetrapeptide Ac-HAEE-NH2 can bind to Aβ via EVHH site. Finally, using two-electrode voltage clamp in Xenopus laevis oocytes, we showed that Ac-HAEE-NH2 tetrapeptide completely abolishes 35 38 the Aβ42-induced inhibition of α4β2 nAChR. Thus, we suggest that HAEE is a potential binding site for Aβ on α4β2 nAChR and Ac-HAEE-NH2 tetrapeptide corresponding to this site is a potential therapeutic for the treatment of α4β2 nAChR-dependent cholinergic dysfunction in AD.

Keywords: Alzheimer’s disease; nicotinic ; cholinergic deficit; peptide drugs; molecular modeling; β-amyloid

1. Introduction Alzheimer’s disease (AD) is the most common neurodegenerative disorder with over 50 million of patients worldwide [1]. Since the approval of by Food and Drug Administration in 2003, no new therapeutics were developed for AD, and no disease-modifying treatments are available [2]. Currently, new therapeutic avenues are being developed on the basis of uncovering the molecular foundations of AD pathogenesis [2]. For a long period, the concepts of AD molecular pathology were focused on the role of amyloid plaques; however, it is becoming clear that neurotoxic oligomers of β-amyloid (Aβ) should be targeted as well [1,3–5]. Soluble neurotoxic Aβ species interact with different

Int. J. Mol. Sci. 2020, 21, 6272; doi:10.3390/ijms21176272 www.mdpi.com/journal/ijms Int. J. Mol. Sci. 2020, 21, 6272 2 of 18 targets, resulting in a systemic impairment of neuronal and glial function [4,6,7]. Important targets of Aβ are brai