The S-100 family of calcium-activated proteins interact with a range of target
proteins to modulate biological signaling pathways. Numerous cancer cell
lines overexpress the plasminogen receptor S-100A10 on the extracellular cell
surface, where it forms a heterotetrameric complex with Annexin II, though
this association is not required for plasma membrane localization or binding
and activation of plasminogen. Additionally, S-100A10 acts as a cellular chaperone
for hepatitis B (Hep B) virus polymerase. Hep B virus polymerase normally
localizes to the cytoplasm only, though in the presence of S-100A10 a
portion relocates to the nucleus, implying a role for S-100A10 and intracellular
calcium in the process of viral replication.