TNFα driven HIF-1α-hexokinase II axis regulates MHC-I cluster stability through actin cytoskeleton

Hypoxia-inducible Factor-la (HIF-1 alpha)-regulated expression of Hexokinase-II (HKII) remains a cornerstone in the maintenance of high metabolic demands subserving various pro -tumor functions including immune evasion in gliomas. Since inflammation-induced HIF-1 alpha regulates Major Histocompatibility Complex class I (MHC-I) gene expression, and as cytoskeletal dynamics affect MHC-I membrane clusters, we investigated the involvement of HIF-1 alpha a-HKII axis in Tumor Necrosis Factor-alpha (TNF alpha)-mediated MHCI membrane cluster stability in glioma cells and the involvement of actin cytoskeleton in the process. TNF alpha increased the clustering and colocalization of MHC-I with cortical actin in a HIF-1 alpha dependent manner. siRNA mediated knockdown of HIF-1 alpha as well as enzymatic inhibition of HK II by Lonidamine, delocalized mitochondrially bound HKII. This altered subcellular HKII localization affected TNFa-induced cofilin activation and actin turnover, as pharmacological inhibition of HKII by Lonidamine decreased Actin -related protein 2 (ARP2)/cofilin interaction. Photobleaching studies revealed destabilization of TNF alpha- induced stable MHC-I membrane clusters in the presence of Lonidamine and ARP2 inhibitor CK666. This work highlights how TNF alpha triggers a previously unknown function of metabolic protein HKII to influence an immune related outcome. Our study establishes the importance of inflammation induced HIF-1 alpha in integrating two crucial components- the metabolic and immune, through reorganization of cytoskeleton. (C) 2015 Elsevier Inc. All rights reserved.