Fig. 4

Cucurbitacin E can bind to the PI3K protein and inhibit its phosphorylation. A Cellular thermal shift assays of the PI3K protein. B Heatmap showing the results of the cellular thermal shift assays of the PI3K protein; the darker the colour, the higher the protein expression level. C Global view of interacting proteins and molecules: Cucurbitacin E–PI3K docking conformation (affinity = − 8.29 kcal/mol). D 3D interaction local view: the PI3K protein secondary structure is shown in the green cartoon, the ligand carbon atoms are shown in magenta, oxygen atoms are shown in red, nitrogen atoms are shown in blue, and the yellow dashed lines indicate hydrogen bonds. Cucurbitacin E formed hydrogen bonds with Lys833 and Asp950 in the protein. E 2D interaction view, with green arrows indicating hydrogen bonds. F Western blotting was performed to measure the expression of PI3K/Akt pathway proteins in IL-1β-stimulated osteoarthritis chondrocytes treated with different concentrations of Cucurbitacin E (1, 5, and 10 nM). G and H The expression of the PI3K/Akt pathway proteins in Figure F was analysed by ImageJ software. I and J SC79 was used to investigate the effect of CuE on IL-1β-stimulated chondrocytes, and ImageJ software was used for quantitative analysis of protein levels. The significance of differences between groups is expressed as P values (***P < 0.001, **P < 0.01, *P < 0.05,^nsP > 0.05)