Annexin A5 stabilizes matrix vesicle-biomimetic lipid membranes: unravelling a new role of annexins in calcification

Eur Biophys J. 2023 Nov 8. doi: 10.1007/s00249-023-01687-4. Online ahead of print.ABSTRACTMatrix vesicles are a special class of extracellular vesicles thought to actively contribute to both physiologic and pathologic mineralization. Proteomic studies have shown that matrix vesicles possess high amounts of annexin A5, suggesting that the protein might have multiple roles at the sites of calcification. Currently, Annexin A5 is thought to promote the nucleation of apatitic minerals close to the inner leaflet of the matrix vesicles' membrane enriched in phosphatidylserine and Ca2+. Herein, we aimed at unravelling a possible additional role of annexin A5 by investigating the ability of annexin A5 to adsorb on matrix-vesicle biomimetic liposomes and Langmuir monolayers made of dipalmitoylphosphatidylserine (DPPS) and dipalmitoylphosphatidylcholine (DPPC) in the absence and in the presence of Ca2+. Differential scanning calorimetry and dynamic light scattering measurements showed that Ca2+ at concentrations in the 0.5-2.0 mM range induced the aggregation of liposomes probably due to the formation of DPPS-enriched domains. However, annexin A5 avoided the aggregation of liposomes at Ca2+ concentrations lower than 1.0 mM. Surface pressure versus surface area isotherms showed that the adsorption of annexin A5 on the monolayers made of a mixture of DPPC and DPPS led to a reduction in the area of excess compared to the theoretical values, which confirmed that the protein favored attracti...

Source: European Biophysics Journal : EBJ - November 8, 2023 Category: Physics Authors: Claudio R Ferreira Marcos Ant ônio E Cruz Mayt ê Bolean Luiz Henrique da S Andrilli Jos é Luis Millan Ana Paula Ramos Massimo Bottini Pietro Ciancaglini Source Type: research