AnxA13

ANXA13 (Annexin A13) is a calcium-dependent phospholipid-binding protein and is widely regarded as the evolutionary founder of the vertebrate annexin family, providing a framework for understanding annexin structure-function relationships and membrane-associated signaling processes^[1][2]. ANXA13 displays highly differentiated, intestine-enriched expression and is associated with intracellular transport and apical membrane trafficking in polarized epithelial cells, where it contributes to the lipid raft-mediated delivery of apical proteins^[1][2][3]. Mechanistically, ANXA13 binds negatively charged membrane phospholipids in a calcium-dependent manner, supporting membrane organization and vesicular transport pathways that are essential for epithelial cell polarity and specialized cellular functions^[2][3]. In experimental systems, ANXA13 expression has been detected in intestinal epithelium, renal tubules, and epithelial structures of the eustachian tube, further supporting a role in apical epithelial biology and tissue-specific membrane dynamics^[4][5]. Disease relevance has recently been demonstrated in acute kidney injury (AKI), where ANXA13 is reduced in injured kidneys and exerts a renoprotective effect by directly interacting with TGF-β receptor type 1, thereby suppressing TGF-β/Smad3 signaling and limiting p21-dependent tubular cell-cycle arrest and cell death^[5]. Compared with other annexin family members, ANXA13 possesses distinctive exon-splicing patterns, intestine-specific expression characteristics, and unique isoforms, including variants containing a KGD motif, highlighting its evolutionary and functional divergence within the annexin superfamily^[1][2]. Currently, no widely established ANXA13-specific agonists or inhibitors have been reported, and most studies employ genetic overexpression, silencing, or knockout approaches to investigate its biological functions and disease-associated mechanisms^[5].