ANXA13 is a calcium-dependent phospholipid-binding protein that functions in membrane organization and cellular signaling. Mechanistically, ANXA13 binds anionic membranes (phosphatidylserine, phosphatidylglycerol) in a calcium-dependent manner, requiring approximately 320 μM calcium for half-maximal binding [UniProt], and induces membrane curvature through fragmented rolling of negatively charged membranes 1. ANXA13 serves dual, context-dependent roles in disease: it is renoprotective in acute kidney injury (AKI) by directly binding TGF-β receptor type 1 and inhibiting Smad3 signaling-mediated tubular cell death 2, whereas it promotes tumorigenesis in multiple cancers. ANXA13 is upregulated in clear cell renal cell carcinoma, lung adenocarcinoma, and colorectal cancer, where it enhances cell proliferation, invasion, and migration while suppressing apoptosis 345. High ANXA13 expression predicts poor prognosis and correlates with lymph node metastasis in colorectal cancer patients 5. Additionally, ANXA13 mediates intracellular transport of ribosome-inactivating proteins 6 and serves as a receptor for bacterial adhesion factors on intestinal epithelial cells 7. ANXA13 shows diagnostic value as a biomarker distinguishing cholangiocellular carcinoma from pancreatic adenocarcinoma 8.