Uroplakin-3b (UPK3B)

Uroplakin-3b (UPK3B) is a **single-pass transmembrane glycoprotein** belonging to the uroplakin family, localized to the apical plasma membrane of **umbrella cells** in the urinary bladder urothelium and to mesothelial cells[1][2]. It forms a heterodimer with Uroplakin-1b in the endoplasmic reticulum, which then contributes to the assembly of two-dimensional urothelial plaque structures called **asymmetric unit membrane (AUM) plaques**[1][2]. These plaques are crucial for **stabilizing the bladder epithelium during distension** and controlling membrane permeability. UPK3B serves as a marker for urothelial differentiation and is highly conserved across species. It is expressed chiefly in the urothelium and mesothelial cells, with restricted expression in other normal tissues[1]. Clinically, UPK3B is a **diagnostic and prognostic biomarker**, particularly helpful in distinguishing mesothelioma from other lung cancers and in assessing stage and outcome in bladder cancer[1]. There are currently **no known therapeutic drugs that directly target UPK3B**, and its primary clinical relevance is as a **biomarker** rather than a therapeutic target.

Other names

Uroplakin 3BUPK3BUroplakin-3bUP3bUPIIIbMGC10902p35FLJ32198Uroplakin IIIbUP3BUPIIIB