title: Muscarinic type 3 receptor induces cytoprotective signaling in salivary gland cells through epidermal growth factor receptor transactivation.
abstract: Muscarinic type 3 receptor (M3R) plays a pivotal role in the induction of glandular fluid secretions. Although M3R is often the target of autoantibodies in Sjögren's syndrome (SjS), chemical agonists for M3R are clinically used to stimulate saliva secretion in patients with SjS. Aside from its activity in promoting glandular fluid secretion, however, it is unclear whether activation of M3R is related to other biological events in SjS. This study aimed to investigate the cytoprotective effect of chemical agonist-mediated M3R activation on apoptosis induced in human salivary gland (HSG) cells. Carbachol (CCh), a muscarinic receptor-specific agonist, abrogated tumor necrosis factor α/interferon γ-induced apoptosis through pathways involving caspase 3/7, but its cytoprotective effect was decreased by a M3R antagonist, a mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (ERK) inhibitor, a phosphatidylinositol 3-kinase/Akt inhibitor, or an epidermal growth factor receptor (EGFR) inhibitor. Ligation of M3R with CCh transactivated EGFR and phosphorylated ERK and Akt, the downstream targets of EGFR. Inhibition of intracellular calcium release or protein kinase C δ, both of which are involved in the cell signaling of M3R-mediated fluid secretion, did not affect CCh-induced ERK or Akt phosphorylation. CCh stimulated Src phosphorylation and binding to EGFR. A Src inhibitor attenuated the CCh/M3R-induced cytoprotective effect and EGFR transactivation cascades. Overall, these results indicated that CCh/M3R induced transactivation of EGFR through Src activation leading to ERK and Akt phosphorylation, which in turn suppressed caspase 3/7-mediated apoptotic signals in HSG cells. This study, for the first time, proposes that CCh-mediated M3R activation can promote not only fluid secretion but also survival of salivary gland cells in the inflammatory context of SjS.
authors.affiliation: Department of Immunology, Forsyth Institute, Cambridge, Massachusetts 02142, USA.
authors.forename: Mikihito
authors.initials: M
authors.lastname: Kajiya
authors.forename: Isao
authors.initials: I
authors.lastname: Ichimonji
authors.forename: Christine
authors.initials: C
authors.lastname: Min
authors.forename: Tongbo
authors.initials: T
authors.lastname: Zhu
authors.forename: Jun-O
authors.initials: JO
authors.lastname: Jin
authors.forename: Qing
authors.initials: Q
authors.lastname: Yu
authors.forename: Soulafa A
authors.initials: SA
authors.lastname: Almazrooa
authors.forename: Seunghee
authors.initials: S
authors.lastname: Cha
authors.forename: Toshihisa
authors.initials: T
authors.lastname: Kawai
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D002118:Calcium / Q000378:metabolism; D002217:Carbachol / Q000494:pharmacology; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D053179:Caspase 7 / Q000235:genetics / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D004815:Epidermal Growth Factor / Q000235:genetics / Q000378:metabolism; D066246:ErbB Receptors / Q000235:genetics* / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007371:Interferon-gamma / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D051745:Protein Kinase C-delta / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000235:genetics / Q000378:metabolism; D043587:Receptor, Muscarinic M3 / Q000819:agonists / Q000235:genetics* / Q000378:metabolism*; D012469:Salivary Glands / Q000187:drug effects / Q000378:metabolism*; D015398:Signal Transduction; D012859:Sjogren's Syndrome / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism; D019061:src-Family Kinases / Q000235:genetics / Q000378:metabolism
chemical_list: D043587:Receptor, Muscarinic M3; D014409:Tumor Necrosis Factor-alpha; D004815:Epidermal Growth Factor; D007371:Interferon-gamma; D002217:Carbachol; D066246:ErbB Receptors; D019061:src-Family Kinases; D051057:Proto-Oncogene Proteins c-akt; D051745:Protein Kinase C-delta; D048049:Extracellular Signal-Regulated MAP Kinases; D053148:Caspase 3; D053179:Caspase 7; D002118:Calcium