Identification of the scavenger receptors SREC-I, Cla-1 (SR-BI), and SR-AI as cellular receptors for Tamm-Horsfall protein.
Tamm-Horsfall protein (THP) is expressed exclusively in the kidney and constitutes the most abundant protein in urine. An important role for THP in antibacterial host defense but also in inflammatory disorders of the urogenital tract has been suggested. In line with this, THP has been shown recently to potently activate macrophages and dendritic cells (DC) via the toll-like receptor 4 (TLR4) pathway. We show here that THP interacts specifically with surface structures on DC and provides evidence that they are distinct from TLR4. Using retroviral expression cloning, we have identified one such receptor as the scavenger receptor (SR) expressed by endothelial cells I (SREC-I). In addition, we found that two other receptors for acetylated low-density lipoprotein (AcLDL), namely scavenger receptors AI (SR-AI) and Cla-1 (SR-BI), also serve as receptors for THP. SREC-I/THP interaction is of high affinity (16.8+/-6.8 nM), whereas Cla-1 and SR-AI have lower affinities for THP (396 nM+/-114 nM and 802 nM+/-157 nM, respectively). The interaction of THP with these molecules is fully blocked by AcLDL. However, AcLDL only partially blocks binding of THP to DC, and a series of experiments did not support a role in DC activation for SR interacting with THP and AcLDL. Thus, our data point to the existence of additional receptors for THP, which mediate TLR4-dependent DC activation. Interaction and up-take of THP by SR might play an important role in local host defense and could contribute to inflammatory kidney diseases associated with THP-specific antibody responses.
Pfistershammer
Katharina
K
Institute of Immunology, Center of Physiology and Pathophysiology, Medical University of Vienna, Borschkegasse 8a, A-1090, Vienna, Austria.
Klauser
Christoph
C
Leitner
Judith
J
Stöckl
Johannes
J
Majdic
Otto
O
Weichhart
Thomas
T
Sobanov
Yuri
Y
Bochkov
Valery
V
Säemann
Marcus
M
Zlabinger
Gerhard
G
Steinberger
Peter
P
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D002478:Cells, Cultured; D003001:Cloning, Molecular; D003713:Dendritic Cells / Q000276:immunology; D006801:Humans; D051379:Mice; D009088:Mucoproteins / Q000276:immunology*; D016133:Polymerase Chain Reaction / Q000379:methods; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D051122:Scavenger Receptors, Class B / Q000235:genetics* / Q000378:metabolism; D051128:Scavenger Receptors, Class F / Q000235:genetics* / Q000378:metabolism; D000068103:Serine-Arginine Splicing Factors; D058949:Uromodulin
D002352:Carrier Proteins; D009088:Mucoproteins; D011956:Receptors, Cell Surface; C503566:SCAF1 protein, human; C495124:SCARB1 protein, human; C495126:SCARF1 protein, human; D051122:Scavenger Receptors, Class B; D051128:Scavenger Receptors, Class F; C548612:UMOD protein, human; C548613:Umod protein, mouse; D058949:Uromodulin; D000068103:Serine-Arginine Splicing Factors