Delivery of Active AKT1 to Human Cells

Delivery of AKT1 phospho-forms to human cells reveals differential substrate selectivity

Protein kinase B (AKT1) is a serine/threonine kinase that regulates fundamental cellular processes, including cell survival, proliferation, and metabolism. AKT1 activity is controlled by two regulatory phosphorylation sites (Thr308, Ser473) that stimulate a downstream signaling cascade through phosphorylation of many target proteins. At either or both regulatory sites, hyperphosphorylation is associated with poor survival outcomes in many human cancers. Our previous biochemical and chemoproteomic studies showed that the phosphorylated forms of AKT1 have differential selectivity toward peptide substrates. Here, we investigated AKT1-dependent activity in human cells, using a cell-penetrating peptide (transactivator of transcription, TAT) to deliver inactive AKT1 or active phospho-variants to cells. We used enzyme engineering and genetic code expansion relying on a phosphoseryl-transfer RNA (tRNA) synthetase (SepRS) and tRNASep pair to produce TAT-tagged AKT1 with programmed phosphorylation at one or both key regulatory sites. We found that all TAT-tagged AKT1 variants were efficiently delivered into human embryonic kidney (HEK 293T) cells and that only the phosphorylated AKT1 (pAKT1) variants stimulated downstream signaling. All TAT-pAKT1 variants induced glycogen synthase kinase (GSK)-3α phosphorylation, as well as phosphorylation of ribosomal protein S6 at Ser240/244, demonstrating stimulation of downstream AKT1 signaling. Fascinatingly, only the AKT1 variants phosphorylated at S473 (TAT-pAKT1S473 or TAT-pAKT1T308,S473) were able to increase phospho-GSK-3β levels. Although each TAT-pAKT1 variant significantly stimulated cell proliferation, cells transduced with TAT-pAKT1T308 grew significantly faster than with the other pAKT1 variants. The data demonstrate differential activity of the AKT1 phospho-forms in modulating downstream signaling and proliferation in human cells.

[Demethylzeylasteral inhibits proliferation, migration and invasion and promotes apoptosis of non-small cell lung cancer cells by inhibiting the AKT/CREB signaling pathway]

OBJECTIVE

To investigate the mechanism underlying the inhibitory effects of Demethylzeylasteral (T-96) on non-small cell lung cancer (NSCLC) cells.

METHODS

We first examined the effects of different concentrations (1, 3, 10, and 30 μmol/L) of demethylzeylasteral on morphology and cell number of A549 and H1299 cells. The changes in proliferation, cell viability, migration, invasion, and apoptosis of A549 and H1299 cells following demethylzeylasteral treatment were detected using clone formation, CCK-8, cell scratch, Transwell, and flow cytometric assays, and the effect of SC79 treatment against demethylzeylasteral-induced cell apoptosis was assessed. Western blotting was performed to detect the changes in expressions of E-cadherin, N-cadherin, vimentin, Bax, Bcl-2 and cleaved caspase-3 and phosphorylation of AKT/CREB in demethylzeylasteral-treated A549 and H1299 cells and the cellular expressions of apoptotic proteins following treatment with both demethylzeylasteral and SC79.

RESULTS

T-96 treatment caused elongation of the cell body and widening of the intercellular space and significantly inhibited cell viability, proliferation, migration and invasion of A549 and H1299 cells (P < 0.05). Flow cytometry showed that demethylzeylasteral induced apoptosis in both A549 and H1299 cells, whereas SC79 treatment obviously attenuated its pro-apoptotic effect (P < 0.05). Western blotting revealed up-regulated expressions of Bax and cleaved caspase-3 proteins and lowered Bcl-2 expression level in demethylzeylasteral-treated A549 and H1299 cells, but cotreatment with SC79 obviously attenuated the expressions of the apoptotic proteins. T-96 significantly up-regulated the expression level of E-cadherin, down-regulated the expressions of N-cadherin and vimentin, and inhibited the phosphorylation of AKT and CREB in the two cell lines (P < 0.05).

CONCLUSION

T-96 inhibits the proliferation, migration and invasion and induces apoptosis of NSCLC cells possibly by inhibiting the AKT/CREB signaling pathway.

Revving the engine: PKB/AKT as a key regulator of cellular glucose metabolism

Glucose metabolism is of critical importance for cell growth and proliferation, the disorders of which have been widely implicated in cancer progression. Glucose uptake is achieved differently by normal cells and cancer cells. Even in an aerobic environment, cancer cells tend to undergo metabolism through glycolysis rather than the oxidative phosphorylation pathway. Disordered metabolic syndrome is characterized by elevated levels of metabolites that can cause changes in the tumor microenvironment, thereby promoting tumor recurrence and metastasis. The activation of glycolysis-related proteins and transcription factors is involved in the regulation of cellular glucose metabolism. Changes in glucose metabolism activity are closely related to activation of protein kinase B (PKB/AKT). This review discusses recent findings on the regulation of glucose metabolism by AKT in tumors. Furthermore, the review summarizes the potential importance of AKT in the regulation of each process throughout glucose metabolism to provide a theoretical basis for AKT as a target for cancers.

Multiple forms of cell death: A focus on the PI3K/AKT pathway

Cell death is a natural biological process that occurs in living organisms. Since 1963, extensive research has shed light on the occurrence, progress, and final outcome of cell death. According to different cell phenotypes, it is classified into different types, including apoptosis, pyroptosis, necroptosis, autophagy, ferroptosis, cuproptosis, and so on. However, regardless of the form of cell death, what we ultimately expect is the disappearance of abnormal cells, such as tumor cells, while normal cells survive. As a result, it is vital to investigate the details of cell death, including death triggers, potent regulators, and executioners. Although significant progress has been made in understanding molecular pathways of cell death, many aspects remain unclear because of the complex regulatory networks in cells. Among them, the phosphoinositide-3-kinase (PI3K)/protein kinase B(AKT) pathway is discovered to be a crucial regulator of the cell death process. AKT, as a proto-oncogene, has become a major focus of attention in the medical community due to its role in regulating a multiplicity of cellular functions counting metabolism, immunity, proliferation, survival, transcription, and protein synthesis. Here, we explored the connection between the PI3K/AKT pathway and cell death, aiming to enhance our comprehension of the mechanism underlying this process. Such knowledge may pave the way for the subsequent development of more effective disease treatments, such as finding suitable targets for drug intervention.

Mechanism of Taxanes in the Treatment of Lung Cancer Based on Network Pharmacology and Molecular Docking

Taxanes are natural compounds for the treatment of lung cancer, but the molecular mechanism behind the effects is unclear. In the present study, through network pharmacology and molecular docking, the mechanism of the target and pathway of taxanes in the treatment of lung cancer was studied. The taxanes targets were determined by PubChem database, and an effective compounds-targets network was constructed. The GeneCards database was used to determine the disease targets of lung cancer, and the intersection of compound targets and disease targets was obtained. The Protein-Protein Interaction (PPI) network of the intersection targets was analyzed, and the PPI network was constructed by Cytoscape 3.6.0 software. The hub targets were screened according to the degree value, and the binding activity between taxanes and hub targets was verified by molecular docking. The results showed that eight taxane-active compounds and 444 corresponding targets were screened out, and 131 intersection targets were obtained after mapping with lung cancer disease targets. The hub targets obtained by PPI analysis were TP53, EGFR, and AKT1. Gene Ontology (GO) biological function enrichment analysis obtained 1795 biological process (BP) terms, 101 cellular component (CC) terms, and 164 molecular function (MF) terms. There were 179 signaling pathways obtained by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. Twenty signaling pathways were screened out, mainly pathways in cancer, proteoglycans in cancer pathway, microRNAs in cancer pathway, and so on. Molecular docking shows that the binding energies of eight taxanes with TP53, EGFR, and AKT1 targets were less than -8.8 kcal/mol, taxanes acts on TP53, EGFR, and AKT1 targets through pathways in cancer, proteoglycans in cancer pathway and microRNAs in cancer pathway, and plays a role in treating lung cancer in biological functions such as protein binding, enzyme binding, and identical protein binding.