Nerve growth factor inhibits apoptosis in memory B lymphocytes via inactivation of p38 MAPK, prevention of Bcl-2 phosphorylation, and cytochrome c release.
Survival of memory B lymphocytes is tightly linked to the integrity of the Bcl-2 protein and is regulated by a nerve growth factor (NGF) autocrine circuit. In factor-starved memory B cells, the addition of exogenous NGF promptly induced p38 mitogen-activated protein kinase (MAPK), but not c-Jun N-terminal kinase (JNK), dephosphorylation. Conversely, withdrawal of endogenous NGF was followed by p38 MAPK activation and translocation onto mitochondria, whereby it combined with and phosphorylated Bcl-2, as assessed by co-immunoprecipitation and kinase assays in vivo and in vitro. Mitochondria isolated from human memory B cells, then exposed to recombinant p38 MAPK, released cytochrome c, as did mitochondria from Bcl-2-negative MDCK cells loaded with recombinant Bcl-2. Apoptosis induced by NGF neutralization could be blocked by the specific p38 MAPK inhibitor SB203580 or by Bcl-2 mutations in Ser-87 or Thr-56. These data demonstrate that the molecular mechanisms underlying the survival factor function of NGF critically rely upon the continuous inactivation of p38 MAPK, a Bcl-2-modifying enzyme.
Torcia
M
M
Department of Experimental Medicine and Internal Medicine, University of Rome "Tor Vergata," Via di Tor Vergata 135, Rome I-00133, Italy. g.torcia@dfc.unifi.it
De Chiara
G
G
Nencioni
L
L
Ammendola
S
S
Labardi
D
D
Lucibello
M
M
Rosini
P
P
Marlier
L N
LN
Bonini
P
P
Dello Sbarba
P
P
Palamara
A T
AT
Zambrano
N
N
Russo
T
T
Garaci
E
E
Cozzolino
F
F
D000818:Animals; D017209:Apoptosis; D001402:B-Lymphocytes / Q000473:pathology*; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D003574:Cytochrome c Group / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D053938:DNA Fragmentation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D007156:Immunologic Memory; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D020932:Nerve Growth Factor / Q000378:metabolism* / Q000502:physiology*; D010766:Phosphorylation; D011233:Precipitin Tests; D011485:Protein Binding; D021381:Protein Transport; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D011994:Recombinant Proteins / Q000378:metabolism; D012694:Serine / Q000737:chemistry; D013912:Threonine / Q000737:chemistry; D013997:Time Factors; D048051:p38 Mitogen-Activated Protein Kinases
D003574:Cytochrome c Group; D004791:Enzyme Inhibitors; D007093:Imidazoles; D019253:Proto-Oncogene Proteins c-bcl-2; D011725:Pyridines; D011994:Recombinant Proteins; D013912:Threonine; D012694:Serine; D020932:Nerve Growth Factor; D048031:JNK Mitogen-Activated Protein Kinases; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; C093642:SB 203580