Research Paper Volume 12, Issue 19 pp 18942—18956

Activation of LKB1 rescues 3T3-L1 adipocytes from senescence induced by Sirt1 knock-down: a pivotal role of LKB1 in cellular aging

Figure 4. (A, B) Western blots of proteins related to and AMPK, LKB1, and Sirt1 signaling and mitochondrial dysfunction at PID 15 in shNegative, shSirt1, and shSirt1+LKB1 K48R cells. p-T172 AMPK and AMPK alpha2 were increased despite decreased p-MARK (LKB1 substrate) in Sirt1 knockdown cells. LKB1 K48R increased p-MARK and decreased p-T172 AMPK. It also significantly upregulated mitochondrial complex I proteins. The ratio of phospho-to-total MARK: A decrease in this ratio indicates a decrease in LKB1 activity caused by Sirt1 knockdown and upregulated by LKB1 K48R expression. Complex 1 expression normalized by HSP90: As seen in (A), expression of LKB1 K48R not only ameliorates LKB1 activity, it also increases mitochondrial complex I expression. (n=4, *p<0.05 vs shNegative). AMPK activity was increased by shSirt1 cells: AMPK activity was assessed by using 32P-ATP in vitro in the SAMS peptide assay. (*p<0.05 vs shNegative, n=6).