Control of neurite outgrowth by RhoA inactivation

• Published in: Journal of neurochemistry 2012-03, Vol.120 (5), p.684-698
• Main Authors: Jeon, Chan-Young, Moon, Mi-Young, Kim, Jong-Hyun, Kim, Hee-Jun, Kim, Jae-Gyu, Li, Yi, Jin, Jae-Kwang, Kim, Pyeung-Hyeun, Kim, Hyoung-Chun, Meier, Kathryn E., Kim, Yong-Sun, Park, Jae-Bong
• Format: Article
• Language: English
• Subjects: Adaptor Proteins, Signal Transducing - metabolism; Adrenals. Adrenal axis. Renin-angiotensin system (diseases); Animals; ARAP3; Axonogenesis; Biological and medical sciences; Brain; Bucladesine - pharmacology; cAMP; Cell Differentiation - drug effects; Cell growth; Complement C3 - pharmacology; Cyclic AMP; Endocrinopathies; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation - drug effects; Gene Expression Regulation - genetics; Guanine; Immunoprecipitation; Isolated neuron and nerve. Neuroglia; Lysophosphatidic acid; Medical sciences; Mimicry; Mutagenesis; Nerve growth factor; Nerve Growth Factor - pharmacology; Neurites - drug effects; Neurites - physiology; Neurochemistry; Neurons - cytology; Neurons - drug effects; Non tumoral diseases. Target tissue resistance. Benign neoplasms; Nucleotides; p190RhoGAP; PC12 cell; PC12 Cells; Pheochromocytoma cells; Phosphorylation; Phosphorylation - drug effects; Phosphorylation - genetics; Proteins; Rap1; rap1 GTP-Binding Proteins - metabolism; Rap1 protein; Rats; Regeneration; RhoA; rhoA GTP-Binding Protein - genetics; rhoA GTP-Binding Protein - metabolism; RhoA protein; Rodents; Src protein; Toxins; Transfection; Vertebrates: nervous system and sense organs
• ISSN: 0022-3042; 1471-4159
• DOI: 10.1111/j.1471-4159.2011.07564.x

J. Neurochem. (2012) 120, 684–698. cAMP induces neurite outgrowth in the rat pheochromocytoma cell line 12 (PC12). In particular, di‐butyric cAMP (db‐cAMP) induces a greater number of primary processes with shorter length than the number induced by nerve growth factor (NGF). db‐cAMP up‐ and down‐regulates GTP‐RhoA levels in PC12 cells in a time‐dependent manner. Tat‐C3 toxin stimulates neurite outgrowth, whereas lysophosphatidic acid (LPA) and constitutively active (CA)‐RhoA reduce neurite outgrowth, suggesting that RhoA inactivation is essential for the neurite outgrowth from PC12 cells stimulated by cAMP. In this study, the mechanism by which RhoA is inactivated in response to cAMP was examined. db‐cAMP induces phosphorylation of RhoA and augments the binding of RhoA with Rho guanine nucleotide dissociation inhibitor (GDI). Moreover, RhoA (S188D) mimicking phosphorylated RhoA induces greater neurite outgrowth than RhoA (S188A) mimicking dephosphorylated form does. Additionally, db‐cAMP increases GTP‐Rap1 levels, and dominant negative (DN)‐Rap1 and DN‐Rap‐dependent RhoGAP (ARAP3) block neurite outgrowth induced by db‐cAMP. DN‐p190RhoGAP and the Src inhibitor PP2 suppress neurite outgrowth, whereas transfection of c‐Src and p190RhoGAP cDNAs synergistically stimulate neurite outgrowth. Taken together, RhoA is inactivated by phosphorylation of itself, by p190RhoGAP which is activated by Src, and by ARAP3 which is activated by Rap1 during neurite outgrowth from PC12 cells in response to db‐cAMP. RhoA inactivation is required for neurite outgrowth of PC12 cells in response to cAMP. Hereby, we elucidated the mechanism of RhoA inactivation by cAMP: the phosphorylation of RhoA and the activation of p190RhoGAP and Rap1/ARAP3 participate in RhoA inactivation. Because neuronal regeneration is induced by RhoA inactivation, Rho inhibitors are emerging as the therapeutic reagents to promote neuronal regeneration.