TM4 peptide, as a representative model of the AChR, conditions its lipid microenvironment.

FABIANI, C.; GEORGIEV, V; DIMOVA. R.; ANTOLLINI, S. S.

REUNIÓN VIRTUAL

Congreso; XLIX Reunión Anual de la Sociedad Argentina de Biofísica; 2021

Sociedad Argentina de Biofísica

Nicotinic acetylcholine receptors (nAChRs) are integral membrane pentameric proteinsthat belong to the Cys-loop superfamily of ligand-gated ion channels. Given that thenAChR is a transmembrane protein, the properties of the membrane where it is embeddedare essential for its correct functioning, and since even small changes in nAChRs activitycan cause great effects on human biology, the interaction between lipids and the nAChRis of great relevance. The transmembrane domain of each subunit of the nAChR iscomposed of four segments (TM1-TM4) in which TM2 segments form the ion channel poreand TM1, TM3, and TM4 are located more externally. TM4 segment is the most exposedand it isin intimate contact with both the surrounding membrane lipids and the rest of thetransmembrane segments, these being two facts that make it a key participant in lipid-nAChR interaction.Due to the abundance of Chol in neural membranes and its importanceand implication in different human diseases, in this work we studied the relationshipbetween domains either rich in cholesterol (Liquid order domains, Lo) or poor incholesterol (Liquid disorder domains, Ld) and the nAChR. To this end, we worked withGUVs, giant unilamellar vesicles that can be observed under the microscope, formed bytwo different lipid compositions (with nanoscopic or microscopic Lo and Ld domains)containing or not a syntheticpeptide corresponding to the TM4 segment of thenAChR.Confocal Fluorescence Microscopy, Fluorescence Recovery After Photobleaching(FRAP) measurements and experiments of Miscibility Transition Temperature showed thatTM4 peptide concentrates in Ld domains. Furthermore, we observed that its presencealters the intrinsic properties of the domains as well as the whole microscopic membraneorganization. It is well known that lipids condition nAChR functioning, here wedemonstrate that just this peptide, as a minimalist but still representative model of thenAChR, can perturb its lipid microenvironment as well.