Insulin-like growth factor-1 (IGF-1) induces the activation/phosphorylation of Akt kinase and cAMP response element-binding protein (CREB) by activating different signaling pathways in PC12 cells.
BACKGROUND
Insulin-like growth factor-1 (IGF-1) is a polypeptide growth factor with a variety of functions in both neuronal and non-neuronal cells. IGF-1 plays anti-apoptotic and other functions by activating multiple signaling pathways including Akt kinase, a serine/threonine kinase essential for cell survival. The nuclear transcription factor cAMP response element-binding protein (CREB) may also be involved although relationships between these two proteins in IGF-1 receptor signaling and protection is not clear, especially in neuronal cells.


RESULTS
IGF-1, in a concentration- and time-dependent manner, induces the activation/phosphorylation of Akt and CREB in PC12 cells by activating different signaling pathways. IGF-1 induced a sustained phosphorylation of Akt while only a transient one was seen for CREB. The phosphorylation of Akt is mediated by the PI3 kinase pathway while that of CREB is dependent on the activation of both MAPK kinase and p38 MAPK. Moreover, the stimulation of PKC attenuated the phosphorylation of Akt induced by IGF-1 while enhancing that of CREB. Survival assays with various kinase inhibitors suggested that the activation/phosphorylation of both Akt and CREB contributes to IGF-1 mediated cell survival in PC12 cells.


CONCLUSIONS
These data suggest that IGF-1 induced the activation of Akt and CREB using distinct pathways in PC12 cells.
Zheng
Wen-Hua
WH
Department of Pharmacology, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China. whzheng123@gmail.com
Quirion
Rémi
R
D000818:Animals; D002470:Cell Survival / Q000187:drug effects / Q000502:physiology; D017362:Cyclic AMP Response Element-Binding Protein / Q000187:drug effects / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000378:metabolism* / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism*; D016716:PC12 Cells; D019869:Phosphatidylinositol 3-Kinases / Q000187:drug effects / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
D017362:Cyclic AMP Response Element-Binding Protein; D004791:Enzyme Inhibitors; D007334:Insulin-Like Growth Factor I; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt