PAI-1 interaction with sortilin-related receptor 1 is required for lung fibrosis
Thomas H. Sisson, John J. Osterholzer, Lisa Leung, Venkatesha Basrur, Alexey Nesvizhskii, Natalya Subbotina, Mark Warnock, Daniel Torrente, Ammara Q. Virk, Sergey S. Gutor, Jeffrey C. Horowitz, Mary Migliorini, Dudley K. Strickland, Kevin K. Kim, Steven K. Huang, Daniel A. Lawrence
Thomas H. Sisson, John J. Osterholzer, Lisa Leung, Venkatesha Basrur, Alexey Nesvizhskii, Natalya Subbotina, Mark Warnock, Daniel Torrente, Ammara Q. Virk, Sergey S. Gutor, Jeffrey C. Horowitz, Mary Migliorini, Dudley K. Strickland, Kevin K. Kim, Steven K. Huang, Daniel A. Lawrence
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Research Article Aging Pulmonology

PAI-1 interaction with sortilin-related receptor 1 is required for lung fibrosis

Abstract

Mutation studies of plasminogen activator inhibitor 1 (PAI-1) have previously implied that PAI-1 promotes lung fibrosis via a vitronectin-dependent (VTN-dependent) mechanism. In the present study, employing 2 distinct murine fibrosis models and VTN-deficient mice, we found that VTN is not required for PAI-1 to drive lung scarring. This result suggested the existence of a profibrotic interaction involving the VTN-binding site on PAI-1 with an unidentified ligand. Using an unbiased proteomic approach, we identified sortilin-related receptor 1 (SorLA) as the most highly enriched PAI-1 binding partner in the fibrosing lung. Investigating the role of SorLA in pulmonary fibrosis demonstrated that deficiency of this protein protected against lung scarring in a murine model. We further found that SorLA is required for PAI-1 to promote scarring in mice, that both SorLA and PAI-1 protein levels are increased in human idiopathic pulmonary fibrosis (IPF) explants, and that these proteins are associated in IPF tissue. Finally, confocal microscopy showed that expression of SorLA in CHO cells increased cellular uptake of PAI-1, and these proteins colocalized in the cytoplasm. Together, these data elucidate a mechanism by which the potent profibrotic mediator PAI-1 drives lung fibrosis and implicate SorLA as a potential therapeutic target in IPF treatment.

Authors

Thomas H. Sisson, John J. Osterholzer, Lisa Leung, Venkatesha Basrur, Alexey Nesvizhskii, Natalya Subbotina, Mark Warnock, Daniel Torrente, Ammara Q. Virk, Sergey S. Gutor, Jeffrey C. Horowitz, Mary Migliorini, Dudley K. Strickland, Kevin K. Kim, Steven K. Huang, Daniel A. Lawrence

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Figure 1

The profibrotic effects of PAI-1 following AEC2 injury are independent of VTN.

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The profibrotic effects of PAI-1 following AEC2 injury are independent o...
(A) Schematics of murine fibrosis models. In the targeted AEC2 injury model, DT (12.5 μg/kg) was administered for 14 days to (i) DTR+ mice, (ii) DTR+:PAI-1–/– mice, (iii) DTR+:VTN–/– mice, and (iv) DTR+:PAI-1–/–:VTN–/– mice. A control cohort of WT (DTR–) mice treated with DT was also included in the study protocol. In the single-dose bleomycin model, bleomycin was administered (2.5 U/kg in 50 μL by the oropharyngeal route) on day 0 to (i) WT mice, (ii) PAI-1–/– mice, (iii) VTN–/– mice, and (iv) double-knockout PAI-1–/–:VTN–/– mice. A group of uninjured WT mice were included as a negative control. (B) In the targeted AEC2 injury model, mice were weighed at regular intervals. (C and E) Lungs were harvested on day 21 (D21) and analyzed for hydroxyproline content. (D and F) BAL samples were obtained on D21 and assayed for total PAI-1 levels. Results in B–F are reported as the mean concentration ± SEM. n = 6–7 (B), n = 7–11 (C), n = 5–11 (D), n = 5–11 (E), and n = 5–8 (F). Representative data are displayed from 1 of 3 (A and B) and 1 of 2 (D) experiments. Significant P values are shown from 2-way ANOVA with Tukey’s multiple-comparison test. (G) H&E- and Picrosirius red–stained D21 lung sections from a representative animal in the targeted AEC2 injury model. Scale bars: 180 μm.