Surfactant protein C (SP-C), a lung-specific hydrophobic peptide that enhances the biophysical activity of surfactant phospholipid, is synthesized as a 21 kD propeptide (proSP-C21) and post-translationally processed to yield a 3.7 kD surface active alveolar form. The importance of SP-C to lung health and disease has been underscored by observations that heterozygous expression of mutations in the SP-C gene (SFTPC) in humans is associated with interstitial lung disease (ILD). Recent studies from our laboratory have: (i) identified a novel PPDY motif in the proSP-C NH2 terminus and its ligand the E3 ligase Nedd4-2 as crucial elements in the targeting of proSP-C to the distal secretory pathway; (ii) functionally characterized the consequences of improper folding of the proSP-C COOH terminus for epithelial cell dysfunction seen with aggregation prone SFTPC mutations (BRICHOS domain) found in patients with accompanying ILD; (iii) uncovered a second class of phenotypically distinct ILD-associated SFTPC mutations (Non-BRICHOS) that, while not ER retained, are instead mistrafficked to non-native organelles. Our published and new preliminary data also indicate that non-BRICHOS SP-C mutants disrupt both endosomal/ lysosomal function as well as macroautophagy producing cytotoxicity by ER stress independent pathways. This project seeks to build upon our long-standing discovery program studying cellular and molecular mechanisms underlying the biosynthetic metabolism of SP-C by further focusing on 3 emerging themes critical to lung cell biology: protein trafficking, organelle homeostasis, and cytoprotection.
Specific Aim 1 will focus on defining the role of 4 key factors, the SP-C NH2 PPDY motif, Nedd4-2 WW domains, proSP-C monoubiquitination, and the adapter protein Golgi-associated, ?-adaptin homologues, Arf-binding protein 3 (GGA3) in anterograde trafficking of proSP-C. In addition, the consequences of proximal retention of proSP-C initiated by disruption of this targeting machinery will be studied using both well-characterized in vitro model systems and a new generation inducible, Cre-recombinase-driven mouse model of Nedd4-2 deficiency to evaluate quality control responses in vivo.
In Specific Aim 2, mechanisms underlying AT2 cell dysfunction and cytotoxicity resulting from expression of mistrafficked non-BRICHOS SP-C mutant isoforms will be evaluated and compared with responses to aggregation prone COOH folding mutants. Results from the proposed studies will enhance our understanding of the molecular mechanisms underlying not only the pathophysiology of AT2 cell dysfunction that accompanies fibrotic lung remodeling in ILD but will provide a framework and model systems for personalized manipulation of proteostasis and cellular signaling for other disorders associated with parenchymal lung disease and epithelial dysfunction.

Public Health Relevance

Pulmonary fibrosis is a devastating interstitial lung disease (ILD) marked by unrelenting respiratory failure and death. It is increasingly recognized that lung epithelial cell dysfunction plays an important role in the pathogenesis of ILD. Supported by evidence that mutations in the Surfactant Protein C (SP-C) gene in humans are associated with cases of lung fibrosis in adults and children, the overall goal of this project is to characterize molecular mechanisms regulating surfactant protein C biosynthesis and the abnormal epithelial cell responses to mutant SP-C expression. Results funded by this project will define the role of the various proteostatic responses used by epithelial cells for cytoprotection and will facilitate development and evaluation of new therapeutic targets for treatment of pulmonary fibrosis.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
4R01HL119436-04
Application #
9069460
Study Section
Lung Injury, Repair, and Remodeling Study Section (LIRR)
Program Officer
Lin, Sara
Project Start
2013-09-09
Project End
2018-05-31
Budget Start
2016-06-01
Budget End
2017-05-31
Support Year
4
Fiscal Year
2016
Total Cost
Indirect Cost
Name
University of Pennsylvania
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Nureki, Shin-Ichi; Tomer, Yaniv; Venosa, Alessandro et al. (2018) Expression of mutant Sftpc in murine alveolar epithelia drives spontaneous lung fibrosis. J Clin Invest 128:4008-4024
Beers, Michael F; Mulugeta, Surafel (2017) The biology of the ABCA3 lipid transporter in lung health and disease. Cell Tissue Res 367:481-493
Beers, Michael F; Knudsen, Lars; Tomer, Yaniv et al. (2017) Aberrant lung remodeling in a mouse model of surfactant dysregulation induced by modulation of the Abca3 gene. Ann Anat 210:135-146
Jacob, Anjali; Morley, Michael; Hawkins, Finn et al. (2017) Differentiation of Human Pluripotent Stem Cells into Functional Lung Alveolar Epithelial Cells. Cell Stem Cell 21:472-488.e10
Beers, Michael F; Moodley, Yuben (2017) When Is an Alveolar Type 2 Cell an Alveolar Type 2 Cell? A Conundrum for Lung Stem Cell Biology and Regenerative Medicine. Am J Respir Cell Mol Biol 57:18-27
Paris, Andrew J; Liu, Yuhong; Mei, Junjie et al. (2016) Neutrophils promote alveolar epithelial regeneration by enhancing type II pneumocyte proliferation in a model of acid-induced acute lung injury. Am J Physiol Lung Cell Mol Physiol 311:L1062-L1075
Kook, Seunghyi; Wang, Ping; Young, Lisa R et al. (2016) Impaired Lysosomal Integral Membrane Protein 2-dependent Peroxiredoxin 6 Delivery to Lamellar Bodies Accounts for Altered Alveolar Phospholipid Content in Adaptor Protein-3-deficient pearl Mice. J Biol Chem 291:8414-27
Atochina-Vasserman, Elena N; Guo, Chang-Jiang; Abramova, Elena et al. (2015) Surfactant dysfunction and lung inflammation in the female mouse model of lymphangioleiomyomatosis. Am J Respir Cell Mol Biol 53:96-104
Mulugeta, Surafel; Nureki, Shin-Ichi; Beers, Michael F (2015) Lost after translation: insights from pulmonary surfactant for understanding the role of alveolar epithelial dysfunction and cellular quality control in fibrotic lung disease. Am J Physiol Lung Cell Mol Physiol 309:L507-25
Hawkins, Arie; Guttentag, Susan H; Deterding, Robin et al. (2015) A non-BRICHOS SFTPC mutant (SP-CI73T) linked to interstitial lung disease promotes a late block in macroautophagy disrupting cellular proteostasis and mitophagy. Am J Physiol Lung Cell Mol Physiol 308:L33-47

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