title: Annexin-A6 presents two modes of association with phospholipid membranes. A combined QCM-D, AFM and cryo-TEM study.
abstract: Annexins are soluble proteins that bind to biological membranes in a Ca(2+)-dependent manner. Annexin-A6 (AnxA6) is unique in the annexin family as it consists of the repeat of two annexin core modules, while all other annexins consist of a single module. AnxA6 has been proposed to participate in various membrane-related processes, including endocytosis and exocytosis, yet the molecular mechanism of association of AnxA6 with biological membranes, especially its ability to aggregate membranes, is still unclear. To address this question, we studied the association of AnxA6 with model phospholipid membranes by combining the techniques of quartz crystal microbalance with dissipation monitoring (QCM-D), (cryo-) transmission electron microscopy (TEM) and atomic force microscopy (AFM). The properties of membrane binding and membrane aggregation of AnxA6 were compared to two reference systems, annexin A5 (AnxA5), which is the annexin prototype, and a chimerical AnxA5-dimer molecule, which is able to aggregate two membranes in a symmetrical manner. We show that AnxA6 presents two modes of association with lipid membranes depending on Ca(2+)-concentration. At low Ca(2+)-concentration ( approximately 60-150microM), AnxA6 binds to membranes via its two coplanar annexin modules and is not able to associate two separate membranes. At high Ca(2+)-concentration ( approximately 2mM), AnxA6 molecules are able to bind two adjacent phospholipid membranes and present a conformation similar to the AnxA6 3D crystallographic structure. Possible biological implications of these novel membrane-binding properties of AnxA6 are discussed.
authors.affiliation: IECB, UMR CBMN CNRS-University Bordeaux-ENITAB, Talence, France.
authors.forename: Nikolay
authors.initials: N
authors.lastname: Buzhynskyy
authors.forename: Marcin
authors.initials: M
authors.lastname: Golczak
authors.forename: Joséphine
authors.initials: J
authors.lastname: Lai-Kee-Him
authors.forename: Olivier
authors.initials: O
authors.lastname: Lambert
authors.forename: Béatrice
authors.initials: B
authors.lastname: Tessier
authors.forename: Céline
authors.initials: C
authors.lastname: Gounou
authors.forename: Rémi
authors.initials: R
authors.lastname: Bérat
authors.forename: Anne
authors.initials: A
authors.lastname: Simon
authors.forename: Thierry
authors.initials: T
authors.lastname: Granier
authors.forename: Jean-Marc
authors.initials: JM
authors.lastname: Chevalier
authors.forename: Serge
authors.initials: S
authors.lastname: Mazères
authors.forename: Joanna
authors.initials: J
authors.lastname: Bandorowicz-Pikula
authors.forename: Slawomir
authors.initials: S
authors.lastname: Pikula
authors.forename: Alain R
authors.initials: AR
authors.lastname: Brisson
mesh_terms: D017304:Annexin A5 / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D017317:Annexin A6 / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D020285:Cryoelectron Microscopy / Q000379:methods*; D006801:Humans; D008567:Membranes, Artificial; D018625:Microscopy, Atomic Force / Q000379:methods*; D010743:Phospholipids / Q000737:chemistry*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure
chemical_list: D017304:Annexin A5; D017317:Annexin A6; D008567:Membranes, Artificial; D010743:Phospholipids; D011994:Recombinant Proteins