Analysis of Ret knockin mice reveals a critical role for IKKs, but not PI 3-K, in neurotrophic factor-induced survival of sympathetic neurons.
We analyzed the survival responses and downstream signaling elicited by GDNF on sympathetic neurons from different Ret knockin mice. Lack of tyrosine 1062, a multidocking site in Ret, completely prevented GDNF-mediated survival. Importantly, lack of tyrosine 981, although abrogating Akt phosphorylation, had no effect on neuronal survival, indicating that the PI 3-K/Akt pathway is not necessary for survival of sympathetic neurons. In contrast, silencing of B-Raf completely prevented not only GDNF-mediated but also NGF-mediated cell survival, independently of MEK-1/2. We identified IKKs as the main effectors of the protective effects of B-Raf. First, B-Raf interacted with and activated IKKs. Second, knockdown of IKKs reversed the protection afforded by a constitutively active form of B-Raf. Third, knockdown of IKKs prevented both NGF- and GDNF-mediated survival. In conclusion, our data delineate a novel survival pathway for sympathetic neurons linking B-Raf to IKKs, independently of both PI 3-K and MEK-1/2 pathways.
Encinas
M
M
Cell Signaling and Apoptosis Group, Departament de Medicina Experimental, Lleida 25198, Spain. mario.encinas@mex.udl.cat
Rozen
E J
EJ
Dolcet
X
X
Jain
S
S
Comella
J X
JX
Milbrandt
J
J
Johnson
E M
EM
D000818:Animals; D048429:Cell Size; D002470:Cell Survival; D002478:Cells, Cultured; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D051100:Glial Cell Line-Derived Neurotrophic Factor / Q000494:pharmacology*; D006801:Humans; D051550:I-kappa B Kinase / Q000502:physiology*; D051379:Mice; D008817:Mice, Mutant Strains; D009154:Mutation; D020932:Nerve Growth Factor / Q000494:pharmacology; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D019869:Phosphatidylinositol 3-Kinases / Q000502:physiology*; D048493:Proto-Oncogene Proteins B-raf / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051096:Proto-Oncogene Proteins c-ret / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013564:Sympathetic Nervous System / Q000166:cytology; D014443:Tyrosine / Q000235:genetics
D051100:Glial Cell Line-Derived Neurotrophic Factor; D014443:Tyrosine; D020932:Nerve Growth Factor; D019869:Phosphatidylinositol 3-Kinases; D051096:Proto-Oncogene Proteins c-ret; C099282:RET protein, human; D048493:Proto-Oncogene Proteins B-raf; D051057:Proto-Oncogene Proteins c-akt; D051550:I-kappa B Kinase; D048049:Extracellular Signal-Regulated MAP Kinases