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Copyright © 2007 by the Rockefeller University Press.
p75 neurotrophin receptor regulates tissue fibrosis through inhibition of plasminogen activation via a PDE4/cAMP/PKA pathwayBenjamin D. Sachs1, George S. Baillie2, Julianne R. McCall1, Melissa A. Passino1, Christian Schachtrup1, Derek A. Wallace2, Allan J. Dunlop2, Kirsty F. MacKenzie2, Enno Klussmann3, Martin J. Lynch2, Shoana L. Sikorski1, Tal Nuriel1,4, Igor Tsigelny1, Jin Zhang1, Miles D. Houslay2, Moses V. Chao4, , and Katerina Akassoglou1
1 Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093 Correspondence to Katerina Akassoglou: akass{at}ucsd.edu Abstract: Clearance of fibrin through proteolytic degradation is a critical step of matrix remodeling that contributes to tissue repair in a variety of pathological conditions, such as stroke, atherosclerosis, and pulmonary disease. However, the molecular mechanisms that regulate fibrin deposition are not known. Here, we report that the p75 neurotrophin receptor (p75NTR), a TNF receptor superfamily member up-regulated after tissue injury, blocks fibrinolysis by down-regulating the serine protease, tissue plasminogen activator (tPA), and up-regulating plasminogen activator inhibitor-1 (PAI-1). We have discovered a new mechanism in which phosphodiesterase PDE4A4/5 interacts with p75NTR to enhance cAMP degradation. The p75NTR-dependent down-regulation of cAMP results in a decrease in extracellular proteolytic activity. This mechanism is supported in vivo in p75NTR-deficient mice, which show increased proteolysis after sciatic nerve injury and lung fibrosis. Our results reveal a novel pathogenic mechanism by which p75NTR regulates degradation of cAMP and perpetuates scar formation after injury. T. Nuriel's present address is Weill Medical School of Cornell University, 1300 York Avenue, New York, NY 10021. J. Zhang's present address is Department of Pharmacology and Molecular Sciences and Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, MD 21205. Abbreviations used in this paper: 3D, three-dimensional; BDNF, brain-derived neurotrophic factor; CGN, cerebellar granule neuron; FL, full length; FRET, fluorescence resonance energy transfer; ICD, intracellular domain; IP, immunoprecipitation; LPS, lipopolysaccharide; MS, multiple sclerosis; NGF, nerve growth factor, p75NTR, p75 neurotrophin receptor; PA, plasminogen activator; PAI-1, plasminogen activator inhibitor-1; PDE, phosphodiesterase; PTX, pertussis toxin; SC, Schwann cell; tPA, tissue plasminogen activator; uPA, urokinase plasminogen activator; wt, wild-type.
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Science Signaling. ISSN 1937-9145 (online), 1945-0877 (print). Pre-2008: Science's STKE. ISSN 1525-8882