PI4KII

PI4KII comprises type II phosphatidylinositol 4-kinases that generate PI(4)P, a lipid signal central to cell signaling, membrane traffic, and vesicle trafficking^[1]. Mechanistically, PI4KIIα acts at endosomes and the trans-Golgi network, where AP-3-dependent sorting requires both its AP-3 sorting motif and kinase-active site^[2]. In lysosomal trafficking, PI4KIIα controls post-Golgi delivery of the LIMP-2/GBA complex, linking PI4P metabolism to Gaucher disease enzyme targeting and sphingolipid homeostasis^[3]. In cancer models, PI4KIIα regulates tumor growth through angiogenesis, HIF-1α expression, and HER-2/PI3K/ERK signaling^[4]. Compared with PI4KIIα, PI4KIIβ is cytosolic and peripheral membrane-associated, recruits to plasma membrane ruffles through Rac, and stimulates PI(4,5)P₂ synthesis at the plasma membrane^[5]. Distinctly, PI4KIIβ suppresses invasive behavior by maintaining MT1-MMP traffic in the degradative pathway and reducing invadopodia formation^[6]. For experimental applications, PI-273 is a substrate-competitive, subtype-specific PI4KIIα inhibitor that reduces PI4P content, AKT signaling, breast cancer cell viability, and MCF-7 tumor growth^[7].