Background/Rationale: We now have established that NEU1 sialidase is expressed in human lung microvascular endothelial cell (HPMEC)s, where it associates with and desialylates CD31, also known as platelet endothelial cell adhesion molecule (PECAM)-1. Further, NEU1 disrupts CD31-driven HPMEC capillary- like tube formation or in vitro angiogenesis. NEU1 requires association with its own chaperone//transport protein, protective protein/cathepsin A (PPCA), for full catalytic activity. We hypothesize that during barrier formation and angiogenesis, as HPMECs engage each other and the CD31-ectodomain (ED)s homophilically interact, the cytoplasmic adapter protein, TNFa Receptor-Associated Factor (TRAF)6, physically associates with and activates one or more src family kinase (SFK)s, which in turn, increases tyrosine phosphorylation of p120 catenin. This phosphoprotein facilitates recruitment of NEU1, most likely accompanied by PPCA, to CD31, permitting removal of sialic acid residues from the CD31-ED and disruption of CD31-driven angiogenesis. Increased NEU1 expression may contribute to the pathogenesis of lung diseases, including Idiopathic pulmonary Fibrosis (IPF). Objective(s): 1. To define the CD31 domain(s) required for its recruitment of NEU1 and/or PPCA in human lung microvascular endothelia. 2. To define the mechanism(s) through which the adapter protein, TRAF6, in concert with one or more SFK(s), regulate NEU1 recruitment to CD31. 3. To define the mechanism(s) through which NEU1 sialidase regulates in vitro EC capillary-like tube formation and in vivo angiogenesis. 4. To establish patterns of NEU1 expression and catalytic activity in the lung tissues of normal subjects and patients with Idiopathic Pulmonary Fibrosis (IPF). Methods: A primary HPMEC system in which NEU1, PPCA, ST6GAL-I, CD31, SFKs, TRAF6, and p120ctn will be manipulated through siRNA technology or infection with adenoviral vectors encoding for wild-type and catalytically-dead NEU1, PPCA, ST6GAL-I, and wild-type and dominant-negative TRAF6. Lung microvascular ECs harvested from wild-type, NEU1-/-, and CD31-/- mice with and without gene rescue will also be studied. Protein-protein interactions will be studied with co-immunoprecipitation, GST-fusion protein pull-down, and Far Western blotting/gel-overlay assays. Finally, angiogenesis will be measured on Matrigel in vitro, and in mice implanted with HPMECs in which expression of NEU1, CD31, SFK(s), TRAF6, and/or p120ctn, have been manipulated. NEU1 mRNA and protein expression will be quantified in lung tissues from IPF patients. Findings/Results: We have established that in postconfluent HPMECs, NEU1 sialidase is recruited to and desialylates CD31.The NEU1-CD31 association is both TRAF6- and SFK-dependent and p120ctn is involved. NEU1 overexpression reduces EC adhesion to extracellular matrix, restrains EC migration into a wound, and impairs in vitro angiogenesis in a CD31-dependent manner. ST6GAL-I counteracts the NEU1 effect. NEU1 expression is increased in the pulmonary vascular endothelium of IPF patients. Status: This project will explore new concepts that are not an extension of any previously funded project(s). Impact: If our proposed studies are successfully completed, they will generate a paradigm shift in which NEU1 can be selectively recruited to specific receptor(s), to regulate their sialylation state(s) and responsiveness. Increased NEU1 expression may mechanistically contribute to IPF pathophysiology.

Public Health Relevance

The ability of one or more endogenous sialidases, such as NEU1, to regulate the proangiogenic pulmonary microvascular endothelial response to injury, inflammation, and tissue remodeling is highly relevant to the pathophysiology of multiple lung diseases that cause morbidity and mortality amongst Veterans, including: asthma, chronic obstructive pulmonary disease, idiopathic pulmonary fibrosis (IPF), acute lung injury, and both primary and metastatic lung cancer. We now have found that NEU1 expression is increased in lung tissues from IPF patients. A mechanistic understanding as to how the sialylation state of one or more receptors expressed on the pulmonary microvascular endothelial surface regulates their responsiveness may offer novel targets for therapeutic intervention.

Agency
National Institute of Health (NIH)
Institute
Veterans Affairs (VA)
Type
Non-HHS Research Projects (I01)
Project #
5I01BX002352-04
Application #
9487858
Study Section
Respiration (PULM)
Project Start
2014-10-01
Project End
2019-03-31
Budget Start
2017-10-01
Budget End
2019-03-31
Support Year
4
Fiscal Year
2018
Total Cost
Indirect Cost
Name
Baltimore VA Medical Center
Department
Type
DUNS #
796532609
City
Baltimore
State
MD
Country
United States
Zip Code
21201
Hyun, Sang W; Liu, Anguo; Liu, Zhenguo et al. (2016) The NEU1-selective sialidase inhibitor, C9-butyl-amide-DANA, blocks sialidase activity and NEU1-mediated bioactivities in human lung in vitro and murine lung in vivo. Glycobiology 26:834-49
Lillehoj, Erik P; Hyun, Sang Won; Liu, Anguo et al. (2015) NEU1 Sialidase Regulates Membrane-tethered Mucin (MUC1) Ectodomain Adhesiveness for Pseudomonas aeruginosa and Decoy Receptor Release. J Biol Chem 290:18316-31
Miranda-Ribera, Alba; Passaniti, Antonino; Ceciliani, Fabrizio et al. (2014) ?1-acid glycoprotein disrupts capillary-like tube formation of human lung microvascular endothelia. Exp Lung Res 40:507-19
Lee, Chunsik; Liu, Anguo; Miranda-Ribera, Alba et al. (2014) NEU1 sialidase regulates the sialylation state of CD31 and disrupts CD31-driven capillary-like tube formation in human lung microvascular endothelia. J Biol Chem 289:9121-35
Lillehoj, Erik P; Hyun, Sang Won; Feng, Chiguang et al. (2014) Human airway epithelia express catalytically active NEU3 sialidase. Am J Physiol Lung Cell Mol Physiol 306:L876-86
Feng, Chiguang; Zhang, Lei; Nguyen, Chinh et al. (2013) Neuraminidase reprograms lung tissue and potentiates lipopolysaccharide-induced acute lung injury in mice. J Immunol 191:4828-37
Liu, Anguo; Gong, Ping; Hyun, Sang W et al. (2012) TRAF6 protein couples Toll-like receptor 4 signaling to Src family kinase activation and opening of paracellular pathway in human lung microvascular endothelia. J Biol Chem 287:16132-45
Cross, Alan S; Hyun, Sang Won; Miranda-Ribera, Alba et al. (2012) NEU1 and NEU3 sialidase activity expressed in human lung microvascular endothelia: NEU1 restrains endothelial cell migration, whereas NEU3 does not. J Biol Chem 287:15966-80
Demirta?, Güne?; Dege, Necmi; Büyükgüngör, Orhan (2011) A third monoclinic polymorph of 3,4,5-trihy-droxy-benzoic acid monohydrate. Acta Crystallogr Sect E Struct Rep Online 67:o1509-10