Regulation of the activity of an antimicrobial peptide by sterols or hopanoids: possible role in cell recognition

Abstract

It is now accepted that hopanoids act as sterol-surrogates in membranes of some sterol-lacking bacteria. Here 10 we inquiry whether the hopanoid diplopterol (DP) could attenuate the activity of the antimicrobial peptide Polybia-MP1 11 (MP1) similarly to cholesterol (CHO). Survival of P. aeruginosa exposed to MP1 was lower for cells incubated with DP than 12 those incubated with CHO, and the affinity and subsequent effect of the peptide on lipid bilayers were different in the 13 presence of DP than in the presence of CHO. Membrane properties showed a non-monotonic behavior as the peptide 14 adsorbed, penetrated, and translocated bilayers with DP suggesting a reorganization of MP1 during these processes. We 15 conclude that MP1 selectivity is finely tuned by lipid composition, and propose the differential interaction and consequent 16 effect promoted by the peptide in membranes with diplopterol as a promising starting point for targeting antimicrobial 17 peptides to hopanoid-containing bacterial membranes. 18Introduction 19 Cell membranes are simultaneously compact and fluid. These properties, which are conserved in different species, have 20 been proposed to be those that are compatible with life (Heimburg, 2007), and it is accepted that sterols are inducers 21 of these particular mechanical conditions in different kingdoms. It has been shown in pioneer works and recent publi-22 cations that hopanoids can be considered sterol-surrogates in sterol-lacking bacteria. Biophysical studies, using artificial 23 membranes, have demonstrated that hopanoids decrease the membrane permeability and increase the membrane or-24 der without compromising their mechanical properties (Sáenz et al., 2012(Sáenz et al., , 2015 Mangiarotti et al., 2019a). In addition, 25 and in accordance with in vitro studies, hopanoids promote resistance to antibiotics, detergents, extreme pHs, high tem-26 perature, oxidation, and high osmolarity in bacteria (Sáenz, 2010; Belin et al., 2018; Welander et al., 2010; Malott et al., 27 2014; Schmerk et al., 2011; Silipo et al., 2014; Kulkarni et al., 2013). 28 Given the similarities between membranes with hopanoids and those with sterols, here we compared the activity of a 29 known antimicrobial peptide (AMP), Polybia-MP1 (MP1, IDWKKLLDAAKQIL-NH 2 ), against membranes with diplopterol (DP, 30 a major hopanoid) or cholesterol (CHO). This peptide, extracted from the venom of the Brazilian wasp Polybia paulista, 31 exhibits bactericidal activity against Gram-positive and Gram-negative bacteria being non-hemolytic and non-cytotoxic 32 (Souza et al., 2005). The aim of this study is to get an insight into the reasons for this peptide behavior, deepening the 33 understanding of the dependence of membrane composition on the MP1-membrane interaction. We inquired whether 34 diplopterol protects membranes from peptide action as good as cholesterol, which hinders membrane disruption by 35 MP1 (Dos Santos Cabrera et al., 2008, 2012. We showed using in vivo assays that the presence of DP prevents the a...