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Biochemistry - Biotechnology - Chemistry - Molecular Biology

Regulation of NF-?B Activation through a Novel PI-3K-Independent and PKA/Akt-Dependent Pathway in Human Umbilical Vein Endothelial Cells
Published: Friday, October 05, 2012
Author: Sakshi Balwani et al.

by Sakshi Balwani, Rituparna Chaudhuri, Debkumar Nandi, Parasuraman Jaisankar, Anurag Agrawal, Balaram Ghosh

The transcription factor NF-?B regulates numerous inflammatory diseases, and proteins involved in the NF-?B-activating signaling pathway are important therapeutic targets. In human umbilical vein endothelial cells (HUVECs), TNF-a-induced I?Ba degradation and p65/RelA phosphorylation regulate NF-?B activation. These are mediated by IKKs (I?B kinases) viz. IKKa, ß and ? which receive activating signals from upstream kinases such as Akt. Akt is known to be positively regulated by PI-3K (phosphoinositide-3-kinase) and differentially regulated via Protein kinase A (PKA) in various cell types. However, the involvement of PKA/Akt cross talk in regulating NF-?B in HUVECs has not been explored yet. Here, we examined the involvement of PKA/Akt cross-talk in HUVECs using a novel compound, 2-methyl-pyran-4-one-3-O-ß-D-2',3',4',6'-tetra-O-acetyl glucopyranoside (MPTAG). We observed that MPTAG does not directly inhibit IKK-ß but prevents TNF-a-induced activation of IKK-ß by blocking its association with Akt and thereby inhibits NF-?B activation. Interestingly, our results also revealed that inhibitory effect of MPTAG on Akt and NF-?B activation was unaffected by wortmannin, and was completely abolished by H-89 treatment in these cells. Thus, MPTAG-mediated inhibition of TNF-a-induced Akt activation was independent of PI-3K and dependent on PKA. Most importantly, MPTAG restores the otherwise repressed activity of PKA and inhibits the TNF-a-induced Akt phosphorylation at both Thr308 and Ser473 residues. Thus, we demonstrate for the first time the involvement of PKA/Akt cross talk in NF-?B activation in HUVECs. Also, MPTAG could be useful as a lead molecule for developing potent therapeutic molecules for diseases where NF-?B activation plays a key role.