title: Identification of a New Exo-Endocytic Mechanism Triggered by Corticotropin-Releasing Hormone in Mast Cells.
abstract: The key role of mast cells (MC), either in development of inflammatory pathologies or in response to environmental stress, has been widely reported in recent years. Previous studies have described the effects of corticotropin-releasing hormone (CRH), which is released from inflamed tissues by cellular stress signals, on MC degranulation, a process possibly driven by selective secretion of mediators (piecemeal degranulation). In this study, we introduce a novel granular exo-endocytic pathway induced by CRH on peritoneal MC. We found that CRH triggers substantial exocytosis, which is even stronger than that induced by Ag stimulation and is characterized by large quantal size release events. Membrane fluorescence increases during stimulation in the presence of FM1-43 dye, corroborating the strength of this exocytosis, given that discrete upward fluorescence steps are often observed and suggesting that secretory granules are preferentially released by compound exocytosis. Additionally, the presence of a depot of large tubular organelles in the cytoplasm suggests that the exocytotic process is tightly coupled to a fast compound endocytosis. This CRH-stimulated mechanism is mediated through activation of adenylate cyclase and an increase of cAMP and intracellular Ca(2+), as evidenced by the fact that the effect of CRH is mimicked by forskolin and 8-bromo-cAMP. Thus, these outcomes constitute new evidence for the critical role of MC in pathophysiological conditions within a cellular stress environment and an alternative membrane trafficking route mediated by CRH.
authors.affiliation: Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, 41009 Seville, Spain.
authors.forename: Santiago
authors.initials: S
authors.lastname: Balseiro-Gomez
authors.affiliation: Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, 41009 Seville, Spain.
authors.forename: Juan A
authors.initials: JA
authors.lastname: Flores
authors.affiliation: Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, 41009 Seville, Spain.
authors.forename: Jorge
authors.initials: J
authors.lastname: Acosta
authors.affiliation: Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, 41009 Seville, Spain.
authors.forename: M Pilar
authors.initials: MP
authors.lastname: Ramirez-Ponce
authors.affiliation: Departamento de Fisiología Médica y Biofísica, Facultad de Medicina, Universidad de Sevilla, 41009 Seville, Spain eales@us.es.
authors.forename: Eva
authors.initials: E
authors.lastname: Ales
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015550:Cell Degranulation / Q000187:drug effects; D002478:Cells, Cultured; D005576:Colforsin / Q000494:pharmacology; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology*; D000242:Cyclic AMP / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects*; D004789:Enzyme Activation / Q000187:drug effects; D005089:Exocytosis / Q000187:drug effects*; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D008407:Mast Cells / Q000378:metabolism* / Q000502:physiology; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal; D011726:Pyridinium Compounds / Q000378:metabolism; D000644:Quaternary Ammonium Compounds / Q000378:metabolism; D017208:Rats, Wistar; D022142:Secretory Vesicles / Q000378:metabolism
chemical_list: C073804:FM1 43; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D005576:Colforsin; D015124:8-Bromo Cyclic Adenosine Monophosphate; D003346:Corticotropin-Releasing Hormone; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D002118:Calcium