Leptin increases axonal growth cone size in developing mouse cortical neurons by convergent signals inactivating glycogen synthase kinase-3beta.
We examined the effects of the adipose hormone leptin on the development of mouse cortical neurons. Treatment of neonatal and adult mice with intraperitoneal leptin (5 mg/kg) induced extracellular signal-regulated kinase (ERK) 1/2 phosphorylation in pyriform and entorhinal cortex neurons. Stimulation of cultured embryonic cortical neurons with leptin evoked Janus kinase 2 and ERK1/2 phosphorylation and activated the downstream effector 90-kDa ribosomal protein S6 kinase. Moreover, leptin elicited the phosphorylation of the phosphatidylinositol 3-kinase effector Akt and evoked Ser-9 phosphorylation of glycogen synthase kinase-3beta (GSK3beta), an event inactivating this kinase. Leptin-mediated GSK3beta phosphorylation was prevented by the MEK/ERK inhibitor PD98059, the phosphatidylinositol 3-kinase inhibitor LY294002, or the protein kinase C inhibitor GF109203X. Exposure of cortical neurons to leptin also induced Ser-41 phosphorylation of the neuronal growth-associated protein GAP-43, an effect prevented by LY294002 and GF109203X but not by PD98059. Ser-41-GAP-43 phosphorylation is usually high in expanding axonal growth cones. Neurons exposed to 100 ng/ml leptin for 72 h displayed reduced rate of growth cone collapse, a shift of growth cone size distribution toward higher values, and a 4-fold increase in mean growth cone surface area compared with control cultures. The leptin-induced growth cone spreading was hampered in cortical neurons from Lepr(db/db) mice lacking functional leptin receptors; it was associated with localized Ser-9-GSK3beta phosphorylation and mimicked by the GSK3beta inhibitor SB216763. At concentrations preventing GSK3beta phosphorylation, PD98059, LY294002, or GF109203X reversed the leptin-induced growth cone surface enlargement. We concluded that the leptin-mediated regulation of growth cone morphogenesis in cortical neurons relies on upstream regulators of GSK3beta activity.
Valerio
Alessandra
A
Center for Study and Research on Obesity, School of Medicine, University of Milan, 20129 Milan, Italy.
Ghisi
Valentina
V
Dossena
Marta
M
Tonello
Cristina
C
Giordano
Antonio
A
Frontini
Andrea
A
Ferrario
Marina
M
Pizzi
Marina
M
Spano
PierFranco
P
Carruba
Michele O
MO
Nisoli
Enzo
E
D000818:Animals; D001369:Axons / Q000378:metabolism*; D002465:Cell Movement; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D020439:Growth Cones / Q000378:metabolism*; D020738:Leptin / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009474:Neurons / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C / Q000037:antagonists & inhibitors
D004791:Enzyme Inhibitors; D020738:Leptin; D000081082:Phosphoinositide-3 Kinase Inhibitors; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D011493:Protein Kinase C; D038362:Glycogen Synthase Kinase 3