Tissue-type plasminogen activator promotes murine myofibroblast activation through LDL receptor-related protein 1-mediated integrin signaling.
The activation of interstitial fibroblasts to become alpha-SMA-positive myofibroblasts is an essential step in the evolution of chronic kidney fibrosis, as myofibroblasts are responsible for the production and deposition of the ECM components that are a hallmark of the disease. Here we describe a signaling pathway that leads to this activation. Tissue-type plasminogen activator (tPA) promoted TGF-beta1-mediated alpha-SMA and type I collagen expression in rat kidney interstitial fibroblasts. This fibrogenic effect was independent of its protease activity but required its membrane receptor, the LDL receptor-related protein 1 (LRP-1). In rat kidney fibroblasts, tPA induced rapid LRP-1 tyrosine phosphorylation and enhanced beta1 integrin recruitment by facilitating the LRP-1/beta1 integrin complex formation. Blockade or knockdown of beta1 integrin abolished type I collagen and alpha-SMA expression. Furthermore, inhibition of the integrin-linked kinase (ILK), a downstream effector of beta1 integrin, or disruption of beta1 integrin/ILK engagement, abrogated the tPA action, whereas ectopic expression of ILK mimicked tPA in promoting myofibroblast activation. In murine renal interstitium after obstructive injury, tPA and alpha-SMA colocalized with LRP-1, and tPA deficiency reduced LRP-1/beta1 integrin interaction and myofibroblast activation. These findings show that tPA induces LRP-1 tyrosine phosphorylation, which in turn facilitates the LRP-1-mediated recruitment of beta1 integrin and downstream ILK signaling, thereby leading to myofibroblast activation. This study implicates tPA as a fibrogenic cytokine that promotes the progression of kidney fibrosis.
Hu
Kebin
K
Department of Pathology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261, USA.
Wu
Chuanyue
C
Mars
Wendy M
WM
Liu
Youhua
Y
D000199:Actins / Q000096:biosynthesis / Q000235:genetics; D000818:Animals; D002460:Cell Line; D002908:Chronic Disease; D024042:Collagen Type I / Q000096:biosynthesis; D005347:Fibroblasts / Q000378:metabolism* / Q000473:pathology; D005355:Fibrosis; D006801:Humans; D019012:Integrin beta1 / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism / Q000473:pathology; D007674:Kidney Diseases / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D032446:Myoblasts / Q000378:metabolism* / Q000473:pathology; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000235:genetics; D010959:Tissue Plasminogen Activator / Q000235:genetics / Q000378:metabolism*; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000378:metabolism; D000099200:Scaffold Protein ILK
D000199:Actins; D024042:Collagen Type I; D019012:Integrin beta1; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D017346:Protein Serine-Threonine Kinases; D010959:Tissue Plasminogen Activator; D053773:Transforming Growth Factor beta1; D000099200:Scaffold Protein ILK; C498862:Acta2 protein, rat