UPK3A is a member of the uroplakin-3 family. Uroplakins （UP） which are transmembrane proteins are important components of the urothelium that pass the lipid bilayer once （UPII， UPIIIa， and UPIIIb） or four times （UPIa and UPIb； both members of the "tetraspanin" family）. All hold great luminal/extracellular domains， but only UPIIIa and UPIIIb have significant cytoplasmic shares in their C-termini. UPK3A is an extremely specific and moderately sensitive immunohistochemical marker for primary and metastatic urothelial carcinomas. Alterations in this gene are related to renal adysplasia.
