ER stress stimulates production of the key antimicrobial peptide, cathelicidin, by forming a previously unidentified intracellular S1P signaling complex

• Published in: Proceedings of the National Academy of Sciences - PNAS 2016-03, Vol.113 (10), p.E1334-E1342
• Main Authors: Park, Kyungho, Ikushiro, Hiroko, Seo, Ho Seong, Shin, Kyong-Oh, Kim, Young il, Kim, Jong Youl, Lee, Yong-Moon, Yano, Takato, Holleran, Walter M., Elias, Peter, Uchida, Yoshikazu
• Format: Article
• Language: English
• Subjects: Animals; Antimicrobial Cationic Peptides - genetics; Antimicrobial Cationic Peptides - metabolism; Biological Sciences; Blotting, Western; Cell Line; Cell Line, Tumor; Cells; Cells, Cultured; Endoplasmic Reticulum Stress; Heat shock proteins; Heat-Shock Proteins - metabolism; Humans; Keratinocytes - cytology; Keratinocytes - metabolism; Lysophospholipids - metabolism; Metabolites; Mice, Knockout; Microscopy, Fluorescence; NF-kappa B - metabolism; Nuclear Pore Complex Proteins - genetics; Nuclear Pore Complex Proteins - metabolism; Peptides; Phosphates; Phosphotransferases (Alcohol Group Acceptor) - genetics; Phosphotransferases (Alcohol Group Acceptor) - metabolism; PNAS Plus; Protein Binding; Receptors, Lysosphingolipid - metabolism; Reverse Transcriptase Polymerase Chain Reaction; RNA-Binding Proteins - genetics; RNA-Binding Proteins - metabolism; Signal Transduction; Sphingosine - analogs & derivatives; Sphingosine - metabolism; TNF Receptor-Associated Factor 2 - genetics; TNF Receptor-Associated Factor 2 - metabolism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.1504555113

We recently identified a previously unidentified sphingosine-1-phosphate (S1P) signaling mechanism that stimulates production of a key innate immune element, cathelicidin antimicrobial peptide (CAMP), in mammalian cells exposed to external perturbations, such as UVB irradiation and other oxidative stressors that provoke subapoptotic levels of endoplasmic reticulum (ER) stress, independent of the well-known vitamin D receptor-dependent mechanism. ER stress increases cellular ceramide and one of its distal metabolites, S1P, which activates NF-κB followed by C/EBPα activation, leading to CAMP production, but in a S1P receptor-independent fashion. We now show that S1P activates NF-κB through formation of a previously unidentified signaling complex, consisting of S1P, TRAF2, and RIP1 that further associates with three stress-responsive proteins; i.e., heat shock proteins (GRP94 and HSP90α) and IRE1α. S1P specifically interacts with the N-terminal domain of heat shock proteins. Because this ER stress-initiated mechanism is operative in both epithelial cells and macrophages, it appears to be a universal, highly conserved response, broadly protective against diverse external perturbations that lead to increased ER stress. Finally, these studies further illuminate how ER stress and S1P orchestrate critical stress-specific signals that regulate production of one protective response by stimulating production of the key innate immune element, CAMP.