title: cAMP-induced auditory supporting cell proliferation is mediated by ERK MAPK signaling pathway.
abstract: Sensorineural hearing deficiencies result from the loss of auditory hair cells. This hearing loss is permanent in humans and mammals because hair cells are not spontaneously replaced. In other animals such as birds, this is not the case. Damage to the avian cochlea evokes proliferation of supporting cells and the generation of functionally competent replacement hair cells. Signal transduction pathways are clinically useful as potential therapeutic targets, so there is significant interest in identifying the key signal transduction pathways that regulate the formation of replacement hair cells. In a previous study from our lab, we showed that forskolin (FSK) treatment induces auditory supporting cell proliferation and formation of replacement hair cells in the absence of sound or aminoglycoside treatment. Here, we show that FSK-induced supporting cell proliferation is mediated by cell-specific accumulation of cyclic adenosine monophosphate (cAMP) in avian supporting cells and the extracellular signal-regulated kinase (ERK) mitogen-activated protein kinase (MAPK) pathway. By a combination of immunostaining and pharmacological analyses, we show that FSK treatment increases cAMP levels in avian auditory supporting cells and that several ERK MAP inhibitors effectively block FSK-induced supporting cell proliferation. Next, we demonstrate by Western blotting and immunostaining analyses the expression of several ERK MAPK signaling molecules in the avian auditory epithelium and the cell-specific expression of B-Raf in avian auditory supporting cells. Collectively, these data suggest that FSK-induced supporting cell proliferation in the avian auditory epithelium is mediated by increases of cAMP levels in supporting cells and the cell-specific expression of the ERK MAPK family member B-Raf in supporting cells.
authors.affiliation: Division of Neuropathology, Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA 19104, USA. tjbell@upenn.edu
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Bell
authors.forename: John Carl
authors.initials: JC
authors.lastname: Oberholtzer
mesh_terms: D000818:Animals; D000963:Antimetabolites / Q000493:pharmacokinetics; D047310:Apigenin / Q000494:pharmacology; D001717:Birds; D001973:Bromodeoxyuridine / Q000493:pharmacokinetics; D002070:Butadienes / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000166:cytology / Q000201:enzymology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D005419:Flavonoids / Q000494:pharmacology; D006198:Hair Cells, Auditory / Q000166:cytology* / Q000201:enzymology*; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology*; D018942:Macrolides / Q000494:pharmacology; D000081412:Myosin VIIa; D009218:Myosins / Q000378:metabolism; D009570:Nitriles / Q000494:pharmacology; D009924:Organ Culture Techniques; D009925:Organ of Corti / Q000166:cytology; D048493:Proto-Oncogene Proteins B-raf / Q000378:metabolism
chemical_list: D000963:Antimetabolites; D002070:Butadienes; D004791:Enzyme Inhibitors; D005419:Flavonoids; C000631455:MYO7A protein, human; D018942:Macrolides; D000081412:Myosin VIIa; D009570:Nitriles; C113580:U 0126; D005576:Colforsin; D047310:Apigenin; D000242:Cyclic AMP; D048493:Proto-Oncogene Proteins B-raf; D048049:Extracellular Signal-Regulated MAP Kinases; D009218:Myosins; D001973:Bromodeoxyuridine; C035359:monorden; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one