Decoding class II PI3K signaling: From membrane identity to human disease.

This review provides an integrated overview of the current understanding of class II PI3Ks, with particular attention to their structural and enzymatic properties, lipid substrate specificity, and emerging roles in membrane trafficking, cellular signaling, and disease. Class II phosphoinositide 3-kinases (PI3Ks) are lipid kinases that regulate membrane identity and intracellular signaling by generating phosphatidylinositol 3-phosphate [PI(3)P] and phosphatidylinositol (3,4)-bisphosphate [PI(3,4)P2] at distinct subcellular compartments. Advances over the past decade have clarified the structural organization, regulatory principles, and lipid output of all the three mammalian isoforms (PI3K-C2α, PI3K-C2β, and PI3K-C2γ). These studies have revealed that class II PI3K function is highly context-dependent, governed by compartment-specific cues and the spatial restriction of lipid products. Dysregulation of class II PI3Ks has been implicated in diverse pathological conditions, including cancer, metabolic disorders, epilepsy, congenital myopathies, vascular dysfunction, and premature aging. These findings establish a framework for understanding how localized phosphoinositide synthesis contributes to cellular homeostasis and disease, and underscore the therapeutic potential of selectively targeting class II PI3K isoforms.