Structures and biological activities of novel phosphatidylethanolamine lipids of Porphyromonas gingivalis

Frank C. Nichols; Birgit Riep; Jiyoung Mun; Martha D. Morton; Toshihisa Kawai; Floyd E. Dewhirst; Michael B. Smith

doi:10.1194/jlr.M500542-JLR200

Structures and biological activities of novel phosphatidylethanolamine lipids of Porphyromonas gingivalis

^*Department of Periodontology, University of Connecticut School of Dental Medicine, Farmington, CT 06030
^†Department of Periodontology and Synoptic Dentistry, Charité-University Medicine Berlin, 13353 Berlin, Germany
^§Department of Chemistry, U3060, University of Connecticut, Storrs, CT 06269
^**Department of Molecular Genetics, The Forsyth Institute, Boston, MA 02115

1To whom correspondence should be addressed. e-mail: nichols{at}nso.uchc.edu

Abstract

The Gram-negative periodontal pathogen Porphyromonas gingivalis synthesizes several classes of novel phosphorylated complex lipids, including the recently characterized phosphorylated dihydroceramides. These sphingolipids promote the interleukin-1 (IL-1)-mediated secretion of inflammatory mediators from fibroblasts, including prostaglandin E₂ and 6-keto prostaglandin F_2α, and alter gingival fibroblast morphology in culture. This report demonstrates that one additional class of phosphorylated complex lipids of P. gingivalis promotes IL-1-mediated secretory responses and morphological changes in cultured fibroblasts. Structural characterization identified the new phospholipid class as 1,2-diacyl phosphatidylethanolamine, which substituted predominantly with isobranched C_15:0 and C_13:0 fatty acids. The isobranched fatty acids, rather than unbranched fatty acids, and the phosphoethanolamine head group were identified as the essential structural elements required for the promotion of IL-1-mediated secretory responses. These structural components are also observed in specific phosphorylated sphingolipids of P. gingivalis and likely contribute to the biological activity of these substances, in addition to the phosphatidylethanolamine lipids described in this report.