Annexin A6-regulator of the EGFR/Ras signalling pathway and cholesterol homeostasis

Abstract

Annexin A6 (AnxA6) belongs to the highly conserved annexin protein family. Like other annexins, the function of AnxA6 is linked to its ability to bind phospholipids in a Ca(2+)-dependent manner, thereby interacting with cellular membranes in a dynamic, reversible and regulated fashion. Upon cell activation, AnxA6 is recruited to the plasma membrane, endosomes and caveolae/membrane rafts to interact with signalling proteins, the endocytic machinery and actin cytoskeleton to inhibit epidermal growth factor receptor and Ras signalling. In addition, AnxA6 associates with late endosomes to regulate cholesterol export leading to reduced cytoplasmic phospholipase A2 activity and caveolae formation. Accordingly, AnxA6 may function as an organizer of membrane domains (i) to create a scaffold for the formation of multifactorial signalling complexes, (ii) to regulate transient membrane-actin interactions during endocytic transport, and (iii) to modulate intracellular cholesterol homeostasis. Altogether, this will regulate critical physiological processes including proliferation, differentiation, inflammation and cell migration.