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Mediators of Inflammation
Volume 2009, Article ID 535348, 8 pages
Research Article

Substance P Increases Cell-Surface Expression of CD74 (Receptor for Macrophage Migration Inhibitory Factor): In Vivo Biotinylation of Urothelial Cell-Surface Proteins

1Research & Development Service, Bay Pines VA Healthcare System, VA Medical Center, Bay Pines, FL 33744, USA
2Department of Molecular Medicine, University of South Florida, Tampa, FL 33620, USA
3Research Service, North Florida/South Georgia Veterans Health System; Department of Medicine, University of Florida College of Medicine, Gainesville, FL 32608, USA
4Division of Urology, Department of Surgery, University of South Florida, Tampa, FL 33620, USA

Received 10 September 2008; Revised 2 December 2008; Accepted 7 January 2009

Academic Editor: Eeva Moilanen

Copyright © 2009 Katherine L. Meyer-Siegler et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Macrophage migration inhibitory factor (MIF), an inflammatory cytokine, and its receptor CD74 are upregulated by bladder inflammation. MIF-mediated signal transduction involves binding to cell-surface CD74, this study documents, in vivo, MIF-CD74 interactions at the urothelial cell surface. N-hydroxysulfosuccinimide biotin ester-labeled surface urothelial proteins in rats treated either with saline or substance P (SP, 40 μg/kg). The bladder was examined by histology and confocal microscopy. Biotinylated proteins were purified by avidin agarose, immunoprecipitated with anti-MIF or anti-CD74 antibodies, and detected with strepavidin-HRP. Only superficial urothelial cells were biotinylated. These cells contained a biotinylated MIF/CD74 cell-surface complex that was increased in SP-treated animals. SP treatment increased MIF and CD74 mRNA in urothelial cells. Our data indicate that intraluminal MIF, released from urothelial cells as a consequence of SP treatment, interacts with urothelial cell-surface CD74. These results document that our previously described MIF-CD74 interaction occurs at the urothelial cell surface.