Fig. 7: Mst1/2 regulate TCF1 expression by promoting the phosphorylation of STAT3.

A, B Flow cytometry analysis (left) and MFI intensity (right) demonstrate the expression levels of p-STAT5, p-S6, p-AKT473 and p-Erk in NK cells from Mst1/2^fl/fl and Mst1/2^fl/flCD122^Cre mice upon stimulation with or without IL-15 (50 ng/mL) for 30 min (n ≥ 4). C Gene-set enrichment analysis of RNA-seq data shows the enrichment of hallmark-IL6-JAK-STAT3-signaling related genes in Mst1/2-deficient NK cells compared to WT NK cells. D Flow cytometry analysis (left) and MFI intensity (right) reveals the expression level of p-STAT3 (Ser727) in NK cells from Mst1/2^fl/fl and Mst1/2^fl/flCD122^Cre mice upon stimulation with or without IL-15 (50 ng/mL) for 30 min (n = 4). E ChIP-qPCR analysis demonstrated binding of p-STAT3 conserved motifs in the Tcf7 5′ regulatory region (−17.5 kb), while no binding was observed in a region without p-STAT3-binding motifs (+0.2 kb), serving as a negative control. The experiments were using sorted NK cells from WT mice with anti-p-STAT3 antibody or isotype-matched IgG. F–I WT splenocytes were treated with DMSO, Mst1 inhibitor XMU-MP-1 (1 mM, MedChemExpress) or p-STAT3 inhibitor Stattic (1 mM, MedChemExpress) for 24 h, followed by flow cytometry analysis. The representative plots (left) and summary data (right) show the expression level of p-STAT3 (F), TCF1 (G), total cellular ROS (H) and the percentage of 7AAD⁺ NK cells (I) (n = 4). J Schematic illustration of Mst1/2 regulate NK cell survival and function via controlling metabolic state and transcriptional activity. Data A, B and D–I are representative of three independent experiments with similar results.