Our goal is to analyze the molecular mechanisms that underlie the formation of tubulointerstitial (TI) fibrosis, to devise more effective therapies to prevent its progression. We study the collagen receptor integrins ?1?1 and showed that it downregulates collagen synthesis, and its loss leads to increased glomerular fibrosis following injury. Integrin ?1?1 plays an anti-fibrotic action by negatively regulating the phosphorylation state of pro-fibrotic growth factor receptors via activation of the tyrosine phosphatase TCPTP. We have also found that integrin ?1?1 is a negative regulator of TI fibrosis, as integrin ?1KO mice show increased unilateral ureteral obstruction-induced fibrosis. Moreover, integrin ?1KO collecting duct (CD) cells have increased activation of TGF-? receptor (T?R)-dependent pro-fibrotic signaling, such as phosphorylated Smad3 and collagen levels. TGF-? exerts its functions via activation of the serine/threonine kinases T?RI and T?RII. Binding of TGF-? to T?RII leads to phosphorylation of T?RI and subsequent activation of the major pro-fibrotic mediator Smad3. Interestingly, the cytoplasmic tail of T?RII can also be phosphorylated on tyrosine residues. However, whether these tyrosines play any physiological or pathological role in renal cells is unknown. The novelty of this proposal is that integrin ?1KO CD cells show increased basal levels of tyrosine phosphorylated T?RII. This result suggests that, in renal cells, integrin ?1?1 crosstalks with T?RII and it might prevent its pro-fibrotic action by downregulating its tyrosine phosphorylation levels. Interestingly, inhibition of TCPTP in CD cells leads to increased Smad3 activation and collagen synthesis. This result, together with the finding that 3 tyrosines in the T?RII tail can be potential substrates of TCPTP, forms the hypothesis that integrin ?1?1 negatively regulates T?RII tyrosine phosphorylation via activation of TCPTP. Thus, we propose that integrin ?1?1/TCPTP-mediated dephosphorylation of T?RII represents an important, but previously undescribed mechanism to selectively reduce T?RII activation and consequent progression of fibrosis. To test this hypothesis:
Aim 1 will analyze the role of T?RII-mediated pro-fibrotic signaling in TI injury in the integrin ?1KO mice. We will cross integrin ?1KO mice with global null or floxed Smad3 mice to determine if preventing T?R/Smad3 axis in the collecting system is sufficient to ameliorate TI fibrosis in the ?1KO mice. We will then determine if in vivo activation of TCPTP is beneficial in the setting of TI injury by counteracting T?R-mediated pro-fibrotic action.
Aim 2 will determine the mechanisms whereby integrin ?1?1 negatively regulates T?RII. We will use in vitro approaches to analyze i) if TCPTP directly binds and dephosphorylates T?RII; ii) if tyrosine residues are important to control T?RII-mediated Smad3 activation and collagen synthesis; and iii) which tyrosine(s) controls T?RII-mediated functions. This study will lead to the identification of a novel crosstalk between integrin ?1?1 an T?RII and, most importantly, a novel mechanism whereby T?RII-mediated pro-fibrotic signaling can be negatively modulated.

Public Health Relevance

Transforming growth factor-? (TGF-?) is widely recognized as one of the key mediators of renal fibrosis leading to chronic kidney disease (CKD); however anti-TGF-? therapy is not effective for the treatment of CKD because 1) TGF-? also exerts beneficial effects; and 2) activation of TGF-? downstream pro-fibrotic signaling can be TGF-? ligand independent. In this proposal, we provide evidence that in the collecting system of the kidney, the collagen receptor integrin ?1?1 crosstalks with the TGF-? receptor II (T?RII) and plays an anti-fibrotic role by negatively regulating T?RII-mediated pro-fibrotic signaling in a ligand independent fashion. Understanding how integrin ?1?1 negatively controls T?RII pro-fibrotic action will contribute to the identification of 1) a novel crosstalk between integrin ?1?1 and T?RII; 2) a novel mechanism whereby T?RIImediated pro-fibrotic signaling can be negatively modulated; and 3) areas where integrin and/or T?RII functions can be specifically targeted to halt and ideally prevent CKD.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
6R01DK095761-05
Application #
9321730
Study Section
Pathobiology of Kidney Disease Study Section (PBKD)
Program Officer
Rys-Sikora, Krystyna E
Project Start
2013-04-08
Project End
2017-03-31
Budget Start
2016-04-30
Budget End
2017-03-31
Support Year
5
Fiscal Year
2016
Total Cost
$238,417
Indirect Cost
$87,520
Name
Vanderbilt University Medical Center
Department
Type
DUNS #
079917897
City
Nashville
State
TN
Country
United States
Zip Code
37232
Albertolle, Matthew E; Phan, Thanh T N; Pozzi, Ambra et al. (2018) Sulfenylation of Human Liver and Kidney Microsomal Cytochromes P450 and Other Drug-Metabolizing Enzymes as a Response to Redox Alteration. Mol Cell Proteomics 17:889-900
Sausville, Lindsay N; Gangadhariah, Mahesha H; Chiusa, Manuel et al. (2018) The Cytochrome P450 Slow Metabolizers CYP2C9*2 and CYP2C9*3 Directly Regulate Tumorigenesis via Reduced Epoxyeicosatrienoic Acid Production. Cancer Res 78:4865-4877
Brown, Kyle L; Banerjee, Surajit; Feigley, Andrew et al. (2018) Salt-bridge modulates differential calcium-mediated ligand binding to integrin ?1- and ?2-I domains. Sci Rep 8:2916
Borza, Corina M; Pozzi, Ambra; Plosa, Erin J (2018) Discoidin Domain Receptor 2, a Potential Therapeutic Target in Lung Fibrosis. Am J Respir Cell Mol Biol 59:277-278
Gewin, Leslie; Zent, Roy; Pozzi, Ambra (2017) Progression of chronic kidney disease: too much cellular talk causes damage. Kidney Int 91:552-560
Sausville, Lindsay N; Jones, Carissa C; Aldrich, Melinda C et al. (2017) Genetic variation in the eicosanoid pathway is associated with non-small-cell lung cancer (NSCLC) survival. PLoS One 12:e0180471
Albertolle, Matthew E; Kim, Donghak; Nagy, Leslie D et al. (2017) Heme-thiolate sulfenylation of human cytochrome P450 4A11 functions as a redox switch for catalytic inhibition. J Biol Chem 292:11230-11242
Borza, Corina M; Su, Yan; Tran, Truc-Linh et al. (2017) Discoidin domain receptor 1 kinase activity is required for regulating collagen IV synthesis. Matrix Biol 57-58:258-271
Kothiwale, Sandeepkumar; Borza, Corina; Pozzi, Ambra et al. (2017) Quantitative Structure-Activity Relationship Modeling of Kinase Selectivity Profiles. Molecules 22:
Mathew, Sijo; Palamuttam, Riya J; Mernaugh, Glenda et al. (2017) Talin regulates integrin ?1-dependent and -independent cell functions in ureteric bud development. Development 144:4148-4158

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