FasL (CD95L/APO-1L) resistance of neurons mediated by phosphatidylinositol 3-kinase-Akt/protein kinase B-dependent expression of lifeguard/neuronal membrane protein 35.
The contribution of Fas (CD95/APO-1) to cell death mechanisms of differentiated neurons is controversially discussed. Rat cerebellar granule neurons (CGNs) express high levels of Fas in vitro but are resistant to FasL (CD95L/APO-1L/CD178)-induced apoptosis. We here show that this resistance was mediated by a phosphatidylinositol 3-kinase (PI 3-kinase)-Akt/protein kinase B (PKB)-dependent expression of lifeguard (LFG)/neuronal membrane protein 35. Reduction of endogenous LFG expression by antisense oligonucleotides or small interfering RNA lead to increased sensitivity of CGNs to FasL-induced cell death and caspase-8 cleavage. The inhibition of PI 3-kinase activity sensitized CGNs to FasL-induced caspase-8 and caspase-3 processing and caspase-dependent fodrin cleavage. Pharmacological inhibition of PI 3-kinase, overexpression of the inhibitory protein IkappaB, or cotransfection of an LFG reporter plasmid with dominant-negative Akt/PKB inhibited LFG reporter activity, whereas overexpression of constitutively active Akt/PKB increased LFG reporter activity. Overexpression of LFG in CGNs interfered with the sensitization to FasL by PI 3-kinase inhibitors. In contrast to CGNs, 12 glioma cell lines, which are sensitive to FasL, did not express LFG. Gene transfer of LFG into these FasL-susceptible glioma cells protected against FasL-induced apoptosis. These results demonstrate that LFG mediated the FasL resistance of CGNs and that, under certain circumstances, e.g., inhibition of the PI 3-kinase-Akt/PKB pathway, CGNs were sensitized to FasL.
Beier
Christoph P
CP
Department of Neurology, Medical School, University of Tübingen, 72076 Tübingen, Germany.
Wischhusen
Jörg
J
Gleichmann
Marc
M
Gerhardt
Ellen
E
Pekanovic
Ana
A
Krueger
Andreas
A
Taylor
Verdon
V
Suter
Ueli
U
Krammer
Peter H
PH
Endres
Matthias
M
Weller
Michael
M
Schulz
Jörg B
JB
D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases / Q000378:metabolism; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology; D053222:Fas Ligand Protein; D005786:Gene Expression Regulation / Q000502:physiology; D005910:Glioma; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009419:Nerve Tissue Proteins / Q000235:genetics* / Q000378:metabolism; D009447:Neuroblastoma; D009474:Neurons / Q000166:cytology* / Q000502:physiology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D011401:Promoter Regions, Genetic / Q000502:physiology; D034741:RNA, Small Interfering; D051381:Rats; D017207:Rats, Sprague-Dawley; D014162:Transfection; D048069:Tumor Necrosis Factors / Q000235:genetics / Q000378:metabolism*
D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases; D053222:Fas Ligand Protein; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D019869:Phosphatidylinositol 3-Kinases; D034741:RNA, Small Interfering; D048069:Tumor Necrosis Factors; C114265:Faim2 protein, rat; C505658:Fasl protein, mouse; C505662:Faslg protein, rat; C505409:Casp3 protein, mouse; C505410:Casp3 protein, rat; C505526:Casp8 protein, mouse; C505528:Casp8 protein, rat