Annexin I targets S100C to early endosomes

Immunofluorescence and subcellular fractionation localize annexin I and the EF hand protein S100C to the same membranous structures which in part correspond to transferrin receptor-positive endosomes. The association of S100C with endosomal membranes is strictly dependent on annexin I binding since a D91stop-S100C mutant protein, in which the residues essential for annexin I binding have been removed, fails to colocalize with membraneous structures. This indicates that annexin I and S100C form a complex in vivo and that the endosomal localization of this complex is mediated through an interaction of annexin I with the endosomal membrane.