Phospholipase C-gamma 1 is required for calcium-induced keratinocyte differentiation

Phospholipase C-gamma 1 is the most abundant member of the phospholipase C family in keratinocytes and is induced by calcium. Phospholipase C-gamma 1, therefore, may be involved in the signal transduction system leading to ca lcium regulation of keratinocyte differentiation. To test this hypothesis, expression of phospholipase C-gamma 1 in human keratinocytes was blocked by transfecting cells with the antisense human phospholipase C-gamma 1 cDNA c onstruct. These cells demonstrated a dramatic reduction in phospholipase C- gamma 1 protein level compared with the empty vector-transfected cells and a marked reduction in the mRNA and protein levels of the differentiation ma rkers involucrin and transglutaminase following administration of calcium. Similarly, cotransfection of antisense phospholipase C-gamma 1 constructs w ith a luciferase reporter vector containing involucrin or transglutaminase promoters led to a substantial reduction in calcium-stimulated involucrin a nd transglutaminase promoter activities. Similar results were seen followin g treatment with a specific phospholipase C inhibitor U73122. To determine whether phospholipase C-gamma 1 regulated differentiation by controlling in tracellular calcium, we examined the ability of antisense phospholipase C-g amma 1 to block the calcium-induced rise in intracellular calcium and found that it could. These findings indicate that phospholipase C-gamma 1 is a c ritical component of the signaling pathway mediating calcium regulation of keratinocyte differentiation via its mobilization of intracellular calcium.