Oral Presentation 2014 International Biophysics Congress

Cooperative binding of annexin A2 to cholesterol and phosphatidylinositol-4,5-biphosphate containing bilayers (#167)

Hans-Joachim Galla 1 , Patrick Druecker 1 , Milena Pejic 1 , David Grill 1 , Volker Gerke 1
  1. University of Muenster, Muenster, Germany

Biological membranes are organized into dynamic microdomains that serve as sites for signal transduction and membrane trafficking. The formation and expansion of these microdomains are driven by intrinsic properties of membrane lipids and integral as well as membrane-associated proteins. Annexin A2 (AnxA2) is a peripherally associated membrane protein that can support microdomain formation in a Ca2+-dependent manner and has been implicated in membrane transport processes. Here we performed a quantitative analysis of the binding of AnxA2 to solid supported membranes containing the annexin binding lipids phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2) and phosphatidylserine (PS) in different compositions. We show that the binding is of high specificity and affinity with dissociation constants ranging between 22.1 and 32.2 nM. We also analyzed binding parameters of a heterotetrameric complex of AnxA2 with its S100A10 protein ligand and show that this complex has a higher affinity for the same membranes with Kd values of 12 to 16.4 nM. Interestingly, binding of the monomeric AnxA2 and the AnxA2-S100A10 complex are characterized by positive cooperativity. By generation and analysis of mutant AnxA2 we also show that this cooperative binding is mediated solely by the conserved C-terminal annexin core domain of the protein. Together our results reveal for the first time that AnxA2 and its derivatives bind cooperatively to membranes containing PS and/or PI(4,5)P2 thus providing a mechanistic model for the lipid clustering activity of AnxA2.