title: Probing the interaction between heparan sulfate proteoglycan with biologically relevant molecules in mimetic models for cell membranes: a Langmuir film study.
abstract: Investigating the role of proteoglycans associated to cell membranes is fundamental to comprehend biochemical process that occurs at the level of membrane surfaces. In this paper, we exploit syndecan-4, a heparan sulfate proteoglycan obtained from cell cultures, in lipid Langmuir monolayers at the air-water interface. The monolayer served as a model for half a membrane, and the molecular interactions involved could be evaluated with tensiometry and vibrational spectroscopy techniques. Polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS) employed in a constant surface pressure regime showed that the main chemical groups for syndecan-4 were present at the air-water interface. Subsequent monolayer decompression and compression showed surface pressure-area isotherms with a large expansion for the lipid monolayers interacting with the cell culture reported to over-express syndecan-4, which was also an indication that the proteoglycan was inserted in the lipid monolayer. The introduction of biological molecules with affinity for syndecam-4, such as growth factors, which present a key role in biochemical process of cell signaling, changed the surface properties of the hybrid film, leading to a model, by which the growth factor binds to the sulfate groups present in the heparan sulfate chains. The polypeptide moiety of syndecan-4 responds to this interaction changing its conformation, which leads to lipid film relaxation and further monolayer condensation.
authors.affiliation: Instituto de Ciências Ambientais, Químicas e Farmacêuticas, Universidade Federal de São Paulo, Diadema, SP, Brazil. lcaseli@unifesp.br
authors.forename: Luciano
authors.initials: L
authors.lastname: Caseli
authors.forename: Renan Pelluzzi
authors.initials: RP
authors.lastname: Cavalheiro
authors.forename: Helena B
authors.initials: HB
authors.lastname: Nader
authors.forename: Carla Cristina
authors.initials: CC
authors.lastname: Lopes
mesh_terms: D000818:Animals; D040761:Biomimetic Materials / Q000737:chemistry*; D002417:Cattle; D002462:Cell Membrane / Q000737:chemistry*; D002478:Cells, Cultured; D008567:Membranes, Artificial; D008956:Models, Chemical; D044367:Phase Transition; D051381:Rats; D053671:Syndecan-4 / Q000737:chemistry* / Q000378:metabolism
chemical_list: D008567:Membranes, Artificial; D053671:Syndecan-4