Neurofibromatosis type I tumor suppressor neurofibromin regulates neuronal differentiation via its GTPase-activating protein function toward Ras.
Neurofibromin, the neurofibromatosis type 1 (NF1) gene product, contains a central domain homologous to a family of proteins known as Ras-GTPase-activating proteins (Ras-GAPs), which function as negative regulators of Ras. The loss of neurofibromin function has been thought to be implicated in the abnormal regulation of Ras in NF1-related pathogenesis. In this study, we found a novel role of neurofibromin in neuronal differentiation in conjunction with the regulation of Ras activity via its GAP-related domain (GRD) in neuronal cells. In PC12 cells, time-dependent increases in the GAP activity of cellular neurofibromin (NF1-GAP) were detected after NGF stimulation, which were correlated with the down-regulation of Ras activity during neurite elongation. Interestingly, the NF1-GAP increase was due to the induction of alternative splicing of NF1-GRD type I triggered by the NGF-induced Ras activation. Dominant-negative (DN) forms of NF1-GRD type I significantly inhibited the neurite extension of PC12 cells via regulation of the Ras state. NF1-GRD-DN also reduced axonal and dendritic branching/extension of rat embryonic hippocampal neurons. These results demonstrate that the mutual regulation of Ras and NF1-GAP is essential for normal neuronal differentiation and that abnormal regulation in neuronal cells may be implicated in NF1-related learning and memory disturbance.
Department of Tumor Genetics and Biology, Kumamoto University School of Medicine, Kumamoto 860-0811, Japan.
Shunji
S
Yunoue
Hiroshi
H
Tokuo
Kohji
K
Fukunaga
Liping
L
Feng
Tatsuya
T
Ozawa
Toru
T
Nishi
Akira
A
Kikuchi
Seisuke
S
Hattori
Junichi
J
Kuratsu
Hideyuki
H
Saya
Norie
N
Araki
D017398:Alternative Splicing / Q000187:drug effects; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002454:Cell Differentiation; D018076:DNA, Complementary / Q000235:genetics; D004815:Epidermal Growth Factor / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D016297:Mutagenesis, Site-Directed; D020932:Nerve Growth Factor / Q000494:pharmacology; D025542:Neurofibromin 1 / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D016716:PC12 Cells; D017434:Protein Structure, Tertiary; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D020703:ras GTPase-Activating Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
D018076:DNA, Complementary; D025542:Neurofibromin 1; D011994:Recombinant Proteins; D020703:ras GTPase-Activating Proteins; D004815:Epidermal Growth Factor; D020932:Nerve Growth Factor