[Frontiers in Bioscience 14, 2494-2503, January 1, 2009]

Multiple activities of a multifaceted receptor: roles of cleaved and soluble uPAR

Nunzia Montuori1, Pia Ragno2

1Department of Cellular and Molecular Biology and Pathology, University "Federico II", Naples, Italy, 2 Department of Chemistry, University of Salerno, Salerno, Italy

TABLE OF CONTENTS

1. Abstract
2. Introduction
3. The uPA receptor
4. uPAR partners and activities
5. Cleaved forms of membrane-bound uPAR: partners and activities
6. Soluble uPAR: partners and activities
7. Cleaved forms of soluble uPAR: partners and activities
7.1. c-suPAR involvement in mobilization of hematopoietic stem cells
8. Summary and perspective
9. Acknowledgement
10. References

1. ABSTRACT

The urokinase-type plasminogen activator receptor (uPAR) is a GPI-anchored cell-surface receptor involved in many physiological and pathological events that include cell migration and tissue invasion. uPAR traditional role was considered the focusing of uPA proteolytic activity on the cell surface; however, different uPAR activities have been demonstrated in the last years. In fact, cell surface uPAR functionally interacts with integrins, fMLP-receptors (fMLP-Rs) and growth factor receptors, thus regulating cell adhesion, migration and proliferation. uPAR also exists in a soluble form (suPAR) that has been detected in human body fluids. Both cell surface and suPAR can be proteolytically cleaved, thus generating truncated forms lacking the N-terminal domain and exposing the specific sequence able to interact with the fMLP-Rs. The cleaved form of suPAR binds and activates the fMLP-Rs and regulates the activity of MCP-1, RANTES and SDF1 receptors. Here, we review the role that shedding and cleavage could play in regulating uPAR structural/functional interaction with other cell-surface receptors and in uPAR-mediated biological and pathological processes.