Do hopanoids mimic sterols properties in membranes?

ELIDA NAHIR PUENTES; DARÍO MARTIN GENOVESE; NATALIA WILKE; AGUSTÍN MANGIAROTTI; CRISTOPH A. NAUMANN

CABA

Simposio; Humboldt Colloquium ?Shaping the Future of German-Argentinian Scientific Cooperation - The Role of Curiosity-Driven Research; 2018

Alexander von Humboldt Foundation

In biological membranes, lipids play multiple roles and thereby influence cell processes, either individually or collectively. The sterols are lipids that have the property of regulating dynamics and maintaining membranes in a microfluid state. While cholesterol is the major sterol in vertebrates, ergosterol plays a key role in fungi, and stigmasterol and sitosterol are the major constituents of sterol profiles of plants species.1 Hopanoids are pentacyclic compounds that are proposed to be sterol surrogates of primitive bacteria.2,3It has been proposed that the sterol modulation of the lipid order emerged as a critical evolutionary step of biological membranes allowing the cells to control their fluidity without compromising their membrane integrity.4 Although prokaryotes lack sterols, it has been demonstrated that hopanoids can form liquid-ordered (Lo) phases in model membranes.3,5 In this manner, the capacity of membranes to form Lo domains, and thus compartmentalize, may be originated before the earth oxygenation and the emergence of sterols and eukaryote organisms.3Despite having proved that Lo phase may be present in the membrane of organisms of different kingdoms, there still is a lack of systematic studies in which the differences and similitudes between the different sterols and hopanoids are evaluated together. In view of this, we have particular interest in developing a systematic platform to study the presence of sterols and hopanoids that regulate the properties of model membranes with liquid-liquid phase coexistence. The first step consists on evaluating the interfacial and diffusional properties of films composed of pure sterols and the hopanoid diplopterol. The aim of this study lies in the comparison of the molecular behavior at the air-water interface. The second step describes binary and ternary lipid mixtures in monolayers and bilayers. This evaluates if the different compounds promote the formation of a liquid-ordered phase based on its distinctive characteristics: retaining of the fluidity while increasing the order of the hydrocarbon chains and decreasing the permeability.(1)     Schaller, H. The Role of Sterols in Plant Growth and Development. Prog. Lipid Res. 2003, 42 (3), 163?175.(2)     Ribeiro, N.; Streiff, S.; Heissler, D.; Elhabiri, M.; Albrecht-Gary, A. M.; Atsumi, M.; Gotoh, M.; Désaubry, L.; Nakatani, Y.; Ourisson, G. Reinforcing Effect of Bi- and Tri-Cyclopolyprenols on ?primitive? Membranes Made of Polyprenyl Phosphates. Tetrahedron 2007, 63 (16), 3395?3407.(3)     Saenz, J. P.; Sezgin, E.; Schwille, P.; Simons, K. Functional Convergence of Hopanoids and Sterols in Membrane Ordering. Proc. Natl. Acad. Sci. 2012, 109 (35), 14236?14240.(4)     Miao, L.; Nielsen, M.; Thewalt, J.; Ipsen, J. H.; Bloom, M.; Zuckermann, M. J.; Mouritsen, O. G. From Lanosterol to Cholesterol: Structural Evolution and Differential Effects on Lipid Bilayers. Biophys. J. 2002, 82 (3), 1429?1444.(5)     Sáenz, J. P.; Grosser, D.; Bradley, A. S.; Lagny, T. J.; Lavrynenko, O.; Broda, M.; Simons, K. Hopanoids as Functional Analogues of Cholesterol in Bacterial Membranes. Proc. Natl. Acad. Sci. U. S. A. 2015, 112 (38), 11971?11976.