Abstract
BackgroundAkt regulates various cellular processes, including cell growth, survival, and metabolism. Recently, Akt's role in neurite outgrowth has also emerged. We thus aimed to identify neuronal function-related genes that are regulated by Akt.MethodsWe performed suppression subtractive hybridization on two previously established PC12 sublines, one of which overexpresses the wild-type (WT) form and the other, the dominant-negative (DN) form of Akt. These sublines respond differently to NGF's neuronal differentiation effect.ResultsA variety of genes was identified and could be classified into several functional groups, one of which was developmental processes. Two genes involved in neuronal differentiation and function were found in this group. v-Maf musculoaponeurotic fibrosarcoma oncogene homolog K (MafK) induces the neuronal differentiation of PC12 cells and immature telencephalon neurons, and synaptotagmin I (SytI) is essential for neurotransmitter release. Another gene, syntenin-1 (Syn-1) was also recognized in the same functional group into which MafK and SytI were classified. Syn-1 has been reported to promote the formation of membrane varicosities in neurons. Quantitative reverse transcription polymerase chain reaction analyses show that the transcript levels of these three genes were lower in PC12 (WT-Akt) cells than in parental PC12 and PC12 (DN-Akt) cells. Furthermore, treatment of PC12 (WT-Akt) cells with an Akt inhibitor resulted in the increase of the expression of these genes and the improvement of neurite outgrowth. These results indicate that dominant-negative or pharmacological inhibition of Akt increases the expression of MafK, SytI, and Syn-1 genes. Using lentiviral shRNA to knock down endogenous Syn-1 expression, we demonstrated that Syn-1 promotes an increase in the numbers of neurites and branches.ConclusionsTaken together, these results indicate that Akt negatively regulates the expression of MafK, SytI, and Syn-1 genes that all participate in regulating neuronal integrity in some way or another.
Highlights
Akt regulates various cellular processes, including cell growth, survival, and metabolism
Nerve growth factor (NGF) 2.5 S was obtained from Roche (NJ, USA) and the iQTM SYBR® Green Supermix came from Bio-Rad (CA, USA)
PC12 (WT-Akt) cells barely differentiate in response to NGF, whereas PC12 (DN-Akt) cells have an accelerated rate of neurite outgrowth [3]
Summary
Akt regulates various cellular processes, including cell growth, survival, and metabolism. Akt has been well recognized as an important regulator for multiple biological processes, including metabolism, cell size, apoptosis, and cell cycle progression [1]. A number of Akt substrates and Akt-regulated genes have been identified, but these are mostly involved in metabolism, cell size, apoptosis, and cell cycle progression These include Gsk, BAD, p21Cip1/ WAF1, p27Kip, and certain transcription factors and transcription factor regulators such as cAMP-response element binding protein (CREB), the FOXO family of Forkhead transcription factors, IκB kinase, and Mdm2 [7,8,9,10,11,12,13,14,15,16]
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