Elucidation of a novel signaling pathway responsible for the roles of phospholipase Cepsilon in augmentation of inflammation and carcinogenesis

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We investigated the molecular mechanisms underlying the augmentation of inflammation by phospholipase Cepsilon (PLCepsilon), an effector of the small GTPases Ras and Rap, as well as its function in whole animals. We found that PLCepsilon plays a role in induction of the proinflammatory cytokine expression by facilitating the nuclear translocation of the transcription factor NF-kappaB upon stimulation of cells with tumor necrosis factor (TNF)-alpha. A candidate of the endogenous ligand was identified that is secreted from TNF-alpha-stimulated cells and induces the PLCepsilon-dependent cytokine expression in an autocrine manner. Moreover, we identified a protein kinase which is activated in a PLCepsilon-dependent manner and presumably involved in the induction of the cytokine expression. Furthermore, from the studies using PLCepsilon knockout mice, we clarified the crucial roles of PLCepsilon in the colitis-induced intestinal carcinogenesis and the pathogenesis of bronchial asthma.