Palate Lung Nasal Clone (PLUNC), a Novel Protein of the Tear Film: Three-Dimensional Structure, Immune Activation, and Involvement in Dry Eye Disease (DED)

Abstract

Citation: Schicht M, Rausch F, Beron M, et al. Palate lung nasal clone (PLUNC), a novel protein of the tear film: three-dimensional structure, immune activation, and involvement in dry eye disease (DED). Invest Ophthalmol Vis Sci. 2015;56:7312-7323. DOI:10.1167/iovs.15-17560 PURPOSE. Palate Lung Nasal Clone (PLUNC) is a hydrophobic protein belonging to the family of surfactant proteins that is involved in fluid balance regulation of the lung. Moreover, it is known to directly act against gram-negative bacteria. The purpose of this study was to investigate the possible expression and antimicrobial role of PLUNC at the healthy ocular surface and in tears of patients suffering from dry eye disease (DED).METHODS. Bioinformatics and biochemical and immunologic methods were combined to elucidate the structure and function of PLUNC at the ocular surface. Tissue-specific localization was performed by using immunohistochemistry. The PLUNC levels in tear samples from non-Sjögren's DED patients with moderate dry eye suffering either from hyperevaporation or tear deficiency were analyzed by ELISA and compared with tears from healthy volunteers.RESULTS. Palate Lung Nasal Clone is expressed under healthy conditions at the ocular surface and secreted into the tear film. Protein modeling studies and molecular dynamics simulations performed indicated surface activity of PLUNC. In vitro experiments revealed that proinflammatory cytokines and bacterial supernatants have only a slight effect on the expression of PLUNC in HCE and HCjE cell lines. In tears from DED patients, the PLUNC concentration is significantly increased (7-fold in evaporative dry eye tears and 17-fold in tears from patients with tear deficiency) compared with healthy subjects. CONCLUSIONS.The results show that PLUNC is a protein of the tear film and suggest that it plays a role in fluid balance and surface tension regulation at the ocular surface.

Tear fluid biomarkers in ocular and systemic disease: potential use for predictive, preventive and personalised medicine

“…This group also found a significant negative correlation of tear MDH2 with clinical parameters, such as tear production and tear quality values, and a positive correlation with soreness symptoms. Recently, a novel protein of the tear film belonging to the family of surfactant proteins, the palate lung nasal clone (PLUNC), has been found to be increased in DED patient tears [ 46 ].…”

SFTA3 – a novel surfactant protein of the ocular surface and its role in corneal wound healing and tear film surface tension

“…The preparation of the samples were performed as previously described by Schicht et al . 15 . All tissue samples were obtained from body donors (5 male, 11 female, aged 33–76 years) donated to the Department of Anatomy and Cell Biology, Martin Luther University Halle-Wittenberg, Germany.…”

“…Tear fluid extraction were performed as previously described by Schicht et al . 15 . Tear fluid samples were collected with Schirmer strips at the Department of Ophthalmology, Friedrich Alexander University Erlangen-Nürnberg, Germany.…”

Tubular lipid binding proteins (TULIPs) growing everywhere

“…CETP/BPI are founders of a much wider protein family of sequence homologues that include the palate lung and nasal epithelial clone (PLUNC, also called BPI fold-containing family, BPIF) proteins. These are highly abundant components of the secretions of upper airways, nasopharynx and tears of mammals [12], [13], [14] and of egg albumen in birds [15], [16]. In addition, there are full length homologues (homology spanning > 450 aa) widely dispersed in all branches of eukaryotic evolution, from fungi to protists, algae and plants.…”