title: Substance P increases cell-surface expression of CD74 (receptor for macrophage migration inhibitory factor): in vivo biotinylation of urothelial cell-surface proteins.
abstract: 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 microg/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.
authors.affiliation: Research & Development Service, Bay Pines VA Healthcare System, VA Medical Center, Bay Pines, FL 33744, USA. katherine.siegler@med.va.gov
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Meyer-Siegler
authors.forename: Shen-Ling
authors.initials: SL
authors.lastname: Xia
authors.forename: Pedro L
authors.initials: PL
authors.lastname: Vera