Enhanced neurogenesis from neural progenitor cells with G1/S-phase cell cycle arrest is mediated by transforming growth factor beta1.
We have previously demonstrated that a G1/S-phase cell cycle blocker, deferoxamine (DFO), increased the number of new neurons from rat neurosphere cultures, which correlated with prolonged expression of cyclin-dependent kinase (cdk) inhibitor p27(kip1) [H. J. Kim et al. (2006)Brain Research, 1092, 1-15]. The present study focuses on neuronal differentiation mechanisms following treatment of neural stem/progenitor cells (NPCs) with a G1/S-phase cell cycle blocker. The addition of DFO (0.5 mm) or aphidicolin (Aph) (1.5 microm) to neurospheres for 8 h, followed by 3 days of differentiation, resulted in an increased number of neurons and neurite outgrowth. DFO induced enhanced expression of transforming growth factor (TGF)-beta1 and cdk5 at 24 h after differentiation, whereas Aph only increased TGF-beta1 expression. DFO-induced neurogenesis and neurite outgrowth were attenuated by administration of a cdk5 inhibitor, roscovitine, suggesting that the neurogenic mechanisms differ between DFO and Aph. TGF-beta1 (10 ng/mL) did not increase neurite outgrowth but rather the number of beta-tubulin III-positive cells, which was accompanied by enhanced p27(kip1) mRNA expression. In addition, TGF-beta receptor type II expression was observed in nestin-positive NPCs. Results indicated that DFO-induced TGF-beta1 signaling activated smad3 translocation from the cytoplasm to the nucleus. In contrast, TGF-beta1 signaling inhibition, via a TGF-beta receptor type I inhibitor (SB-505124), resulted in decreased DFO-induced neurogenesis, in conjunction with decreased p27(kip1) protein expression and smad3 translocation to the nucleus. These results suggest that cell cycle arrest during G1/S-phase induces TGF-beta1 expression. This, in turn, prompts enhanced neuronal differentiation via smad3 translocation to the nucleus and subsequent p27(kip1) activation in NPCs.
Misumi
Sachiyo
S
Department of Neurophysiology and Brain Science, Nagoya City University Graduate School of Medical Sciences, Mizuho-ku, Nagoya 467-8601, Japan.
Kim
Tae-Sun
TS
Jung
Cha-Gyun
CG
Masuda
Tadashi
T
Urakawa
Susumu
S
Isobe
Yoshiaki
Y
Furuyama
Fujiya
F
Nishino
Hitoo
H
Hida
Hideki
H
D000818:Animals; D016590:Aphidicolin / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D051360:Cyclin-Dependent Kinase 5 / Q000235:genetics / Q000378:metabolism; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics / Q000378:metabolism; D003676:Deferoxamine / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D016193:G1 Phase / Q000187:drug effects / Q000502:physiology*; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D011247:Pregnancy; D051381:Rats; D017208:Rats, Wistar; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D016196:S Phase / Q000187:drug effects / Q000502:physiology*; D017262:Siderophores / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D051900:Smad3 Protein / Q000378:metabolism; D013234:Stem Cells / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D053773:Transforming Growth Factor beta1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D014404:Tubulin / Q000378:metabolism
D004791:Enzyme Inhibitors; D018125:Receptors, Transforming Growth Factor beta; D017262:Siderophores; D051900:Smad3 Protein; C497787:Smad3 protein, rat; D053773:Transforming Growth Factor beta1; D014404:Tubulin; D050760:Cyclin-Dependent Kinase Inhibitor p27; D016590:Aphidicolin; D051360:Cyclin-Dependent Kinase 5; C495907:Cdk5 protein, rat; C049301:microtubule-associated protein-2 phosphatase; D010749:Phosphoprotein Phosphatases; D003676:Deferoxamine; D004298:Dopamine