Mitogenic signaling of urokinase receptor-deficient kidney fibroblasts: actions of an alternative urokinase receptor and LDL receptor-related protein.
The urokinase receptor (uPAR) attenuates myofibroblast recruitment and fibrosis in the kidney. This study examined the role of uPAR and its co-receptor LDL receptor-related protein (LRP) in the regulation of kidney fibroblast proliferation and extracellular signal-regulated kinase (ERK) signaling. Compared with uPAR+/+ cells, uPAR-/- kidney fibroblasts were hyperproliferative. UPAR-/- fibroblast proliferation was 60% inhibited by an ERK kinase inhibitor. LRP protein was reduced and extracellular accumulation of urokinase-type plasminogen activator (uPA) and plasminogen activator inhibitor type 1 (PAI-1) proteins were greater in uPAR-/- cultures. Addition of functional uPA protein or LRP antisense RNA significantly increased ERK signaling and cell mitosis in both genotypes. Enhanced uPAR-/- fibroblast proliferation was reversed by a recombinant nonfunctional uPA peptide. The density of cell-bound fluor-uPA was similar between uPAR-/- and uPAR+/+ fibroblasts (78 +/- 6 versus 92 +/- 16 units). These data suggest that uPAR-deficient kidney fibroblasts express lower levels of its scavenger co-receptor LRP, resulting in greater extracellular accumulation of uPA and PAI-1. Enhanced proliferation of uPAR-/- fibroblasts seems to be mediated by uPA-dependent ERK signaling via an alternative urokinase receptor.
University of Washington, Children's Hospital and Regional Medical Center, Division of Nephrology, Seattle, WA 98105, USA.
Guoqiang
G
Zhang
Xiaohe
X
Cai
Jesús M
JM
López-Guisa
Sarah J
SJ
Collins
Allison A
AA
Eddy
D000818:Animals; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology*; D007668:Kidney / Q000166:cytology* / Q000201:enzymology / Q000473:pathology; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010641:Phenotype; D010766:Phosphorylation; D017395:Plasminogen Activator Inhibitor 1 / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics* / Q000378:metabolism*; D055293:Receptors, Urokinase Plasminogen Activator; D014517:Ureteral Obstruction / Q000378:metabolism / Q000473:pathology; D014568:Urokinase-Type Plasminogen Activator / Q000378:metabolism / Q000494:pharmacology
D026503:Low Density Lipoprotein Receptor-Related Protein-1; D017395:Plasminogen Activator Inhibitor 1; C524899:Plaur protein, mouse; D011956:Receptors, Cell Surface; D055293:Receptors, Urokinase Plasminogen Activator; D020928:Mitogen-Activated Protein Kinases; D014568:Urokinase-Type Plasminogen Activator