PAK1 Promotes Gluconeogenesis Via the ACSS2/KAT2A/PCK1 Complex to Attenuate Steatotic Liver Ischemia-Reperfusion Injury.

Ischemia-reperfusion (IR) injury is particularly severe in steatotic livers, substantially increasing the risk of graft failure. The growing use of steatotic grafts amid donor shortages has therefore heightened the clinical importance of this problem. The conserved serine/threonine kinase p21-activated kinase 1 (PAK1) regulates cell migration, growth, and redox homeostasis, but its role in steatotic liver IR injury remains unclear. To address this question, we examined the association between PAK1 expression in human steatotic liver grafts and clinical outcomes in 74 liver transplantation (LT) recipients. Liver function, inflammation, and apoptosis were assessed using liver enzyme assays, F4/80 and Ly-6G immunostaining, and TUNEL staining, respectively. Co-immunoprecipitation and RNA sequencing were performed to elucidate the underlying molecular mechanisms. High PAK1 levels in steatotic liver grafts were associated with improved graft function and recipient survival after LT. Consistent with these clinical findings, PAK1 knockout exacerbated IR-induced hepatic inflammation and hepatocyte apoptosis, whereas PAK1 overexpression conferred protection; these findings were corroborated in vitro. Mechanistically, PAK1 interacted directly with ACSS2 and mediated ACSS2 phosphorylation at S267. Phosphorylated ACSS2 subsequently recruited KAT2A to form a multiprotein complex that locally catalyzed PCK1 K547 lactylation, thereby promoting gluconeogenesis. This process suppressed reactive oxygen species (ROS) production and enhanced energy supply. Moreover, fingolimod effectively protected steatotic livers against IR injury in the experimental model. Together, these findings highlight PAK1 as an important regulator of gluconeogenesis through the ACSS2-KAT2A-PCK1 complex and provide new insights into therapeutic strategies for protecting steatotic liver grafts against IR injury.