Loss of phospholipase C δ1 impairs keratinocyte differentiation and epidermal barrier

Abstract

Phospholipase C (PLC) is a key enzyme in phosphoinositide turnover, an important signal transduction process in cells. PLC activation leads to various cellular responses through mobilization of intracellular calcium ion and protein kinase C activation. There are 13 PLC isozymes in mammals. Among them, one of PLC isozymes, PLCδ1 is abundantly expressed in differentiated layers of epidermis, suggesting that PLCδ1 plays important roles in epidermal differentiation. In this study, we examined whether loss of PLCδ1 affected differentiation of human keratinocyte. siRNA-mediated silencing of PLCδ1 revealed that PLCδ1-deficient organotypic skin culture showed decreased intensity of lypophilic dye staining in the stratum corneum. In addition, filaggrin showed broader expression in the stratum corneum of PLCδ1-deficient organotypic skin culture by immunohistochemistry. Furthermore, silencing of PLCδ1 resulted in abnormal tight junction (TJ) formation in human primary keratinocytes. Since stratum corneum lipids, filaggrin, and TJ play critical roles in formation and maintenance of the cutaneous barrier, we investigated whether loss of PLCδ1 affected barrier functions by lucifer yellow permeability assay. Lucifer yellow permeability was enhanced in PLCδ1-deficient organotypic skin culture, indicating that outside-inside barrier was impaired in PLCδ1-deficient organotypic skin culture. Taken together, our results indicate that loss of PLCδ1 disturbed keratinocyte differentiation and epidermal barrier.