Influence of the 524-VAAEIL-529 sequence of annexins A6 in their interfacial behavior and interaction with lipid monolayers.

Annexin A6 (AnxA6), a calcium- and membrane-binding protein, is expressed in mammalian cells in two isoforms: AnxA6-1 and AnxA6-2, the latter lacking the 524-VAAEIL-529 sequence at the start of repeat 7. The different intracellular localization of these two isoforms suggests distinct function in membrane dynamics. The aim of this work was to analyze the behavior of AnxA6 isoforms at the air/water interface alone and in the presence of membrane mimicking lipid monolayers.

Interaction of AnxA6 with isolated and artificial lipid microdomains; importance of lipid composition and calcium content.

Niemann-Pick type C (NPC) disease is a lipid storage disorder characterized by accumulation of lipids in the late endosome/lysosome (LE/LY) compartment. In our previous report we isolated membranes of the LE/LY compartment from NPC L1 skin fibroblasts with a mutation in the NPC1 gene and found that they were characterized by low fluidity which likely contributed to the impaired function of membrane proteins involved in storage and turnover of cholesterol. In this report we isolated lipid microdomains (DRMs) from membranes of various cellular compartments and observed an increased amount of DRMs in the LE/LY compartment of NPC L1 cells in comparison to control cells, with no change in the DRM content in the plasma membrane.

Annexin A6 is recruited into lipid rafts of Niemann-Pick type C disease fibroblasts in a Ca2+-dependent manner.

Niemann-Pick type C (NPC) disease is characterized by excessive accumulation of cholesterol in the late endosome/lysosome compartment. Some members of the annexin family of proteins such as annexin A2 (AnxA2) and annexin A6 (AnxA6) follow the same route as cholesterol during the endocytic pathway and are found, as AnxA6, attached to the membranes of the cholesterol storage compartment in NPC disease fibroblasts. Therefore, the purpose of this work was to test the hypothesis that AnxA6 participates in the NPC-induced changes in the organization of membrane microdomains resistant to solubilization by a nonionic detergent, Triton X-100, i.

Interaction of annexin A6 with cholesterol rich membranes is pH-dependent and mediated by the sterol OH.

Annexin A6 (AnxA6), a calcium- and membrane-binding protein, is well-known to play a role in calcium homeostasis, membrane traffic and membrane organization. It had been suggested that, despite calcium-dependent interaction with anionic phospholipids, AnxA6 displays calcium-independent cholesterol binding properties. In this study, the following questions were addressed: does AnxA6 bind preferentially to cholesterol-containing biomimetic membranes? If so, what is the molecular mechanism of the binding? To answer these questions, human recombinant AnxA6-1 isoform was prepared and used with Langmuir monolayers containing various lipids.