title: On multivalent receptor activity of GM1 in cholesterol containing membranes.
abstract: Gangliosides located at the outer leaflet of plasma membrane are molecules that either participate in recognizing of exogenous ligand molecules or exhibit their own receptor activity, which are both essential phenomena for cell communication and signaling as well as for virus and toxin entry. Regulatory mechanisms of lipid-mediated recognition are primarily subjected to the physical status of the membrane in close vicinity of the receptor. Concerning the multivalent receptor activity of the ganglioside GM1, several regulatory strategies dealing with GM1 clustering and cholesterol involvement have been proposed. So far however, merely the isolated issues were addressed and no interplay between them investigated. In this work, several advanced fluorescence techniques such as Z-scan fluorescence correlation spectroscopy, Förster resonance energy transfer combined with Monte Carlo simulations, and a newly developed fluorescence antibunching assay were employed to give a more complex portrait of clustering and cholesterol involvement in multivalent ligand recognition of GM1. Our results indicate that membrane properties have an impact on a fraction of GM1 molecules that is not available for the ligand binding. While at low GM1 densities (~1 %) it is the cholesterol that turns GM1 headgroups invisible, at higher GM1 level (~4 %) it is purely the local density of GM1 molecules that inhibits the recognition. At medium GM1 content, cooperation of the two phenomena occurs. This article is part of a Special Issue entitled: Nanoscale membrane organisation and signalling.
authors.affiliation: Department of Biophysical Chemistry, J. Heyrovsky Institute of Physical Chemistry of the Academy of Sciences of the Czech Republic, Dolejškova 2155/3, Prague 8, Cz-182 23, Czech Republic. Electronic address: radek.sachl@jh-inst.cas.cz.
authors.forename: Radek
authors.initials: R
authors.lastname: Šachl
authors.affiliation: Department of Biophysical Chemistry, J. Heyrovsky Institute of Physical Chemistry of the Academy of Sciences of the Czech Republic, Dolejškova 2155/3, Prague 8, Cz-182 23, Czech Republic. Electronic address: mariana.amaro@jh-inst.cas.cz.
authors.forename: Mariana
authors.initials: M
authors.lastname: Amaro
authors.affiliation: Department of Biophysical Chemistry, J. Heyrovsky Institute of Physical Chemistry of the Academy of Sciences of the Czech Republic, Dolejškova 2155/3, Prague 8, Cz-182 23, Czech Republic. Electronic address: gokcan.aydogan@jh-inst.cas.cz.
authors.forename: Gokcan
authors.initials: G
authors.lastname: Aydogan
authors.affiliation: Department of Biophysical Chemistry, J. Heyrovsky Institute of Physical Chemistry of the Academy of Sciences of the Czech Republic, Dolejškova 2155/3, Prague 8, Cz-182 23, Czech Republic; Faculty of Science, Charles University in Prague, Albertov 6, 128 43, Prague 2, Czech Republic. Electronic address: alenakoukalova@seznam.cz.
authors.forename: Alena
authors.initials: A
authors.lastname: Koukalová
authors.affiliation: Shemyakin- Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Science, Ul. Miklukho-Maklaya, 16/10, 117997 Moscow, GSP-7, Russian Federation. Electronic address: ilya.mikhalyov@gmail.com.
authors.forename: Ilya I
authors.initials: II
authors.lastname: Mikhalyov
authors.affiliation: Shemyakin- Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Science, Ul. Miklukho-Maklaya, 16/10, 117997 Moscow, GSP-7, Russian Federation. Electronic address: ivan@lipids.ibch.ru.
authors.forename: Ivan A
authors.initials: IA
authors.lastname: Boldyrev
authors.affiliation: Department of Biophysical Chemistry, J. Heyrovsky Institute of Physical Chemistry of the Academy of Sciences of the Czech Republic, Dolejškova 2155/3, Prague 8, Cz-182 23, Czech Republic. Electronic address: jana.humpolickova@jh-inst.cas.cz.
authors.forename: Jana
authors.initials: J
authors.lastname: Humpolíčková
authors.affiliation: Department of Biophysical Chemistry, J. Heyrovsky Institute of Physical Chemistry of the Academy of Sciences of the Czech Republic, Dolejškova 2155/3, Prague 8, Cz-182 23, Czech Republic. Electronic address: martin.hof@jh-inst.cas.cz.
authors.forename: Martin
authors.initials: M
authors.lastname: Hof
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D002784:Cholesterol; D016000:Cluster Analysis; D003198:Computer Simulation; D004058:Diffusion; D031541:Fluorescence Resonance Energy Transfer; D005677:G(M1) Ganglioside / Q000737:chemistry / Q000378:metabolism*; D006834:Hydrazines / Q000378:metabolism; D008024:Ligands; D009010:Monte Carlo Method; D011956:Receptors, Cell Surface / Q000378:metabolism*; D012756:Sheep; D017186:Titrimetry
chemical_list: D006834:Hydrazines; D008024:Ligands; D011956:Receptors, Cell Surface; D005677:G(M1) Ganglioside; D002784:Cholesterol
keywords: Antibunching; Cholera toxin; Energy transfer; Fluorescence correlation spectroscopy; Gangliosides