Abstract
Glial cell line-derived neurotrophic factor (GDNF) increases survival and neurite extension of spiral ganglion neurons (SGNs), the primary neurons of the auditory system, via yet unknown signaling mechanisms. In other cell types, signaling is achieved by the GPI-linked GDNF family receptor α1 (GFRα1) via recruitment of transmembrane receptors: Ret (re-arranged during transformation) and/or NCAM (neural cell adhesion molecule). Here we show that GDNF enhances neuritogenesis in organotypic cultures of spiral ganglia from 5-day-old rats and mice. Addition of GFRα1-Fc increases this effect. GDNF/GFRα1-Fc stimulation activates intracellular PI3K/Akt and MEK/Erk signaling cascades as detected by Western blot analysis of cultures prepared from rats at postnatal days 5 (P5, before the onset of hearing) and 20 (P20, after the onset of hearing). Both cascades mediate GDNF stimulation of neuritogenesis, since application of the Akt inhibitor Wortmannin or the Erk inhibitor U0126 abolished GDNF/GFRα1-Fc stimulated neuritogenesis in P5 rats. Since cultures of P5 NCAM-deficient mice failed to respond by neuritogenesis to GDNF/GFRα1-Fc, we conclude that NCAM serves as a receptor for GDNF signaling responsible for neuritogenesis in early postnatal spiral ganglion.
| Original language | English |
|---|---|
| Journal | Molecular and Cellular Neuroscience |
| Volume | 54 |
| Pages (from-to) | 30-43 |
| Number of pages | 14 |
| ISSN | 1044-7431 |
| DOIs | |
| Publication status | Published - 01.05.2013 |
Funding
We thank Dr. Gary D. Housley (University of New South Wales, Sydney) for advice on neurite labeling in whole mount preparations and Brendan Brinkman (UCSD) for continuous technical support at UCSD's confocal microscopy core facility. We thank Dr. Constantini (Columbia University, New York) for generously providing the Ret KO mouse line. Achim Dahlmann (Zentrum fuer Molekulare Neurobiologie Hamburg) and Sylvia Grammerstorf-Rosche (University of Lübeck) helped with genotyping of the NCAM mutant mouse line. We thank Edgar Kramer (Zentrum fuer Molekulare Neurobiologie Hamburg) for donation of various Ret antibodies and fruitful discussions on Ret Western blotting results. Financial support was obtained from the Medical Research and Rehabilitation Research and Development Services of the VASDHS (1IRX000977, to A.F.R.), the NIH/NIDCD ( DC000139 , to A.F.R.), the German Research Foundation (DFG, EU 120/1-1 to S.E.) and the Lübeck University, School of Medicine ( E28-2009 to S.E.). UCSD's microscopy core facility is supported by NINDS grant NS047101 . The authors declare no conflict of interest.
