The death receptor antagonist FLIP-L interacts with Trk and is necessary for neurite outgrowth induced by neurotrophins.
FLICE-inhibitory protein (FLIP) is an endogenous inhibitor of the signaling pathway triggered by the activation of death receptors. Here, we reveal a novel biological function for the long form of FLIP (FLIP-L) in neuronal differentiation, which can be dissociated from its antiapoptotic role. We show that FLIP-L is expressed in different regions of the mouse embryonic nervous system. Immunohistochemistry of mouse brain sections at different stages reveals that, in neurons, FLIP is expressed early during the embryonic neuronal development (embryonic day 16) and decreases at later stages (postnatal days 5-15), when its expression is essentially detected in glial cells. FLIP-L overexpression significantly enhances neurotrophin-induced neurite outgrowth in motoneurons, superior cervical ganglion neurons, and PC12 cells. Conversely, the downregulation of FLIP-L protein levels by specific RNA interference significantly reduces neurite outgrowth, even in the presence of the appropriate neurotrophin stimulus. Moreover, NGF-dependent activation of two main intracellular pathways involved in the regulation of neurite outgrowth, extracellular signal-regulated kinases (ERKs) and nuclear factor kappaB (NF-kappaB), is impaired when endogenous FLIP-L is downregulated, although TrkA remains activated. Finally, we demonstrate that FLIP-L interacts with TrkA, and not with p75(NTR), in an NGF-dependent manner, and endogenous FLIP-L interacts with TrkB in whole-brain lysates from embryonic day 15 mice embryos. Altogether, we uncover a new role for FLIP-L as an unexpected critical player in neurotrophin-induced mitogen-activated protein kinase/ERK- and NF-kappaB-mediated control of neurite growth in developing neurons.
Moubarak
Rana S
RS
Institut de Neurociències, Departament de Bioquímica i Biologia Molecular, Facultat de Medicina, Universitat Autònoma de Barcelona, Campus de Bellaterra (Edifici M), 08193 Bellaterra, Spain.
Solé
Carme
C
Pascual
Marta
M
Gutierrez
Humberto
H
Llovera
Marta
M
Pérez-García
M José
MJ
Gozzelino
Raffaella
R
Segura
Miguel F
MF
Iglesias-Guimarais
Victoria
V
Reix
Stéphanie
S
Soler
Rosa M
RM
Davies
Alun M
AM
Soriano
Eduardo
E
Yuste
Victor J
VJ
Comella
Joan X
JX
D000818:Animals; D001921:Brain / Q000196:embryology / Q000254:growth & development / Q000502:physiology*; D053446:CASP8 and FADD-Like Apoptosis Regulating Protein / Q000378:metabolism*; D016923:Cell Death / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D051379:Mice; D009046:Motor Neurons / Q000502:physiology; D016328:NF-kappa B / Q000378:metabolism; D009414:Nerve Growth Factors / Q000378:metabolism*; D009419:Nerve Tissue Proteins; D016501:Neurites / Q000502:physiology*; D055495:Neurogenesis / Q000502:physiology*; D009457:Neuroglia / Q000378:metabolism; D016716:PC12 Cells; D051381:Rats; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D020917:Receptor, trkA / Q000378:metabolism; D020813:Receptor, trkB / Q000378:metabolism; D017978:Receptors, Growth Factor; D017475:Receptors, Nerve Growth Factor / Q000378:metabolism; D017783:Superior Cervical Ganglion / Q000196:embryology / Q000254:growth & development / Q000502:physiology
D053446:CASP8 and FADD-Like Apoptosis Regulating Protein; D016328:NF-kappa B; D009414:Nerve Growth Factors; D009419:Nerve Tissue Proteins; D017978:Receptors, Growth Factor; D017475:Receptors, Nerve Growth Factor; C517634:Ngfr protein, mouse; C068313:Ngfr protein, rat; D020794:Receptor Protein-Tyrosine Kinases; D020917:Receptor, trkA; D020813:Receptor, trkB; D048049:Extracellular Signal-Regulated MAP Kinases