Fig. 1

The urokinase plasminogen activator receptor (uPAR). a While usually quiescent in normal tissue, uPAR expression is observed transiently and locally during specific cellular processes such as extravasation and migration by wound healing. b At a cellular level, uPAR interacts in a multitude of pathways where the balance of each dictates the end result. c uPAR itself is a three domain extracellular structure linked to the plasma membrane by a glycosylphosphatidylinositol (GPI) anchor. d Classically uPAR functions as receptor for urokinase plasminogen activator (uPA) which subsequently breaks down the extracellular matrix (ECM) via plasminogen activation. e Intracellular signaling occurs via other receptors including vitronectin and integrins and can be uPA dependent and independent. f Internalization and recycling of uPAR occurs after a uPAR/uPA/PAI-1/LRP-1 complex has formed, which results in the degradation of uPA and PAI-1 and the recycling of uPAR and LRP-1. g uPAR can be cleaved at the GPI-anchor and between D1 and D2 resulting in various isoforms of soluble uPAR which can be quantified in the blood. h After cleavage of D1, uPAR D2-D3 induces chemotaxis by interacting with formyl peptide receptor-like 1 (FPRL1)