TGFbeta, which exists in 3 isoforms, is a pleiotropic cytokine involved in a variety of lung processes and diseases, e.g., development, pulmonary fibrosis, tuberculosis, asthmatic airway remodeling and cancer. TGFbeta bioavailability is tightly regulated in the extracellular space: TGFbeta is secreted in a latent form, which is sequestered in matrix binding sites by the action of an adapter protein (LTBP), and must be activated before it can signal via TGFbeta receptors. TGFbeta latency occurs as a result of binding to the TGFbeta propeptide Latency-Associated Peptide (LAP), and activation involves releasing TGFbeta from LAP. Because all TGFbeta signaling occurs subsequent to TGFbeta activation, the activation mechanisms are critical control points. Mechanisms of TGFbeta activation have been proposed (e.g., thrombospondin-1, proteases and oxidants), but their roles in vivo are unclear. We showed that an epithelium-specific integrin, alphaVbeta6, binds latent TGFbeta1 at an RGD sequence within LAP. Cells expressing alphaVbeta6 activate TGFbeta1, and mice lacking alphaVbeta6 do not develop bleomycin-induced pulmonary fibrosis. We have also shown that alphaVbeta6 can activate TGFbeta3, and that another integrin expressed in lung epithelium (alphaVbeta8) can activate TGFbeta1/3. The goal of this work is to define the role of integrin-mediated TGFbeta1 activation in vivo. To that end, we have generated knockin mice with a mutation in the TGFbeta1 gene that encodes a nonfunctional integrin-binding site in the LAP propeptide. The phenotype of these mice (designated TGFbeta1-RGE) reproduces the most prominent aspect of the TGFbeta1-/- phenotype: severe, multiorgan inflammation that causes death at 3-4 weeks of age. This important finding suggests the possibility that integrin-mediated TGFbeta1 activation occurs upstream of most TGFbeta1 effects.
The specific aims of this work are to (1) characterize the TGFbeta1-RGE mice in comparison to TGFbeta1-/- mice, (2) test the hypothesis that the only TGFbeta1-activating integrins in vivo are alphaVbeta6 and alphaVbeta8, and (3) test the hypothesis that the phenotype of certain integrin KO mice (alphaV-/- and (beta8-/-) is due to combined lack of TGFbeta1 and TGFbeta3 activation. These studies will further delineate the role of RGD-binding integrins in TGFbeta biology and provide a basis for important studies of their role in lung pathology.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL063786-06
Application #
6921339
Study Section
Lung Injury, Repair, and Remodeling Study Section (LIRR)
Program Officer
Reynolds, Herbert Y
Project Start
2000-02-07
Project End
2008-06-30
Budget Start
2005-07-01
Budget End
2006-06-30
Support Year
6
Fiscal Year
2005
Total Cost
$422,500
Indirect Cost
Name
New York University
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
121911077
City
New York
State
NY
Country
United States
Zip Code
10016
Liu, Li; Kugler, Matthias C; Loomis, Cynthia A et al. (2013) Hedgehog signaling in neonatal and adult lung. Am J Respir Cell Mol Biol 48:703-10
Aluwihare, Poshala; Mu, Zhenyu; Zhao, Zhicheng et al. (2009) Mice that lack activity of alphavbeta6- and alphavbeta8-integrins reproduce the abnormalities of Tgfb1- and Tgfb3-null mice. J Cell Sci 122:227-32
Aluwihare, Poshala; Munger, John S (2008) What the lung has taught us about latent TGF-beta activation. Am J Respir Cell Mol Biol 39:499-502
Mu, Zhenyu; Yang, Zhiwei; Yu, Dawen et al. (2008) TGFbeta1 and TGFbeta3 are partially redundant effectors in brain vascular morphogenesis. Mech Dev 125:508-16
Puthawala, Khalid; Hadjiangelis, Nicos; Jacoby, Steven C et al. (2008) Inhibition of integrin alpha(v)beta6, an activator of latent transforming growth factor-beta, prevents radiation-induced lung fibrosis. Am J Respir Crit Care Med 177:82-90
Yang, Zhiwei; Mu, Zhenyu; Dabovic, Branka et al. (2007) Absence of integrin-mediated TGFbeta1 activation in vivo recapitulates the phenotype of TGFbeta1-null mice. J Cell Biol 176:787-93
Annes, Justin P; Munger, John S; Rifkin, Daniel B (2003) Making sense of latent TGFbeta activation. J Cell Sci 116:217-24
Annes, Justin P; Rifkin, Daniel B; Munger, John S (2002) The integrin alphaVbeta6 binds and activates latent TGFbeta3. FEBS Lett 511:65-8
Mu, Dezhi; Cambier, Stephanie; Fjellbirkeland, Lars et al. (2002) The integrin alpha(v)beta8 mediates epithelial homeostasis through MT1-MMP-dependent activation of TGF-beta1. J Cell Biol 157:493-507