SAB is an outer membrane docking protein for JNK mediated impaired mitochondrial function. Deletion of Sab in hepatocytes inhibits sustained JNK activation and cell death. Current work demonstrated that increasing SAB enhanced the severity of APAP liver injury. Female mice were resistant to liver injury and exhibited markedly decreased hepatic SAB protein expression versus males. The mechanism of SAB repression involved a pathway from ERα to p53 expression which induced miR34a-5p. miR34a-5p targeted the Sab mRNA coding region, repressing SAB expression. Fulvestrant or p53 knockdown decreased miR34a-5p and increased SAB in females leading to increased injury from APAP and TNF/galactosamine. In contrast, ERα agonist increased p53 and miR34a-5p which decreased SAB expression and hepatotoxicity in males. Hepatocyte-specific deletion of miR34a also increased severity of liver injury in females, which was prevented by GalNAc-ASO knockdown of Sab. Similar to mice, premenopausal human females also expressed high hepatic p53 and low SAB levels while age-matched males expressed low p53 and high SAB levels, but there was no sex difference of SAB expression in postmenopause. In conclusion, the level of SAB expression determined the severity of JNK dependent liver injury. Females expressed low hepatic SAB protein levels due to an ERα-p53-miR34a pathway which repressed SAB expression, accounting for resistance to liver injury.
Sanda Win, Robert W.M. Min, Christopher Q. Chen, Jun Zhang, Yibu Chen, Meng Li, Ayako Suzuki, Manal F. Abdelmalek, Ying Wang, Mariam Aghajan, Filbert W.M. Aung, Anna Mae Diehl, Roger J. Davis, Tin A. Than, Neil Kaplowitz