Up‐regulation of cofilin‐1 in cell senescence associates with morphological change and p27(kip1)‐mediated growth delay

Morphological change is an explicit characteristic of cell senescence, but the underlying mechanisms remains to be addressed. Here, we demonstrated, after a survey of various actin‐binding proteins, that the post‐translational up‐regulation of cofilin‐1 was essential for the reduced rate of actin depolymerization morphological enlargement in senescent cells. Additionally, up‐regulated cofilin‐1 mainly existed in the serine‐3 phosphorylated form, according to the 2D gel immunoblotting assay. The up‐regulation of cofilin‐1 was also detected in aged mammalian tissues. The over‐expression of wild‐type cofilin‐1 and constitutively phosphorylated cofilin‐1 promoted cell senescence with an increased cell size. Additionally, senescent phenotypes were also reduced by knockdown of total cofilin‐1, which led to a decrease in phosphorylated cofilin‐1. The senescence induced by the over‐expression of cofilin‐1 was dependent on p27(Kip1), but not on the p53 and p16(INK4) expressions. The knockdown of p27(Kip1) alleviated cell senescence induced by oxidative stress or replicative stress. We also found that the over‐expression of cofilin‐1 induced the expression of p27(Kip1) through transcriptional suppression of the transcriptional enhancer factors domain 1 (TEAD1) transcription factor. The TEAD1 transcription factor played a transrepressive role in the p27(Kip1) gene promoter, as determined by the promoter deletion reporter gene assay. Interestingly, the down‐regulation of TEAD1 was accompanied by the up‐regulation of cofilin‐1 in senescence. The knockdown and restoration of TEAD1 in young cells and old cells could induce and inhibit p27(Kip1) and senescent phenotypes, respectively. Taken together, the current data suggest that cofilin‐1/TEAD1/p27(Kip1) signaling is involved in senescence‐related morphological change and growth arrest.