Prodifferentiative role of PKD1 in human hTert keratinocytes

hTert keratinocytes have been obtained from normal human epidermal keratinocytes, which were infected with amphotropic retroviral vectors encoding hTert, the catalytic subunit of telomerase. It was previously supposed that immortalization of keratinocytes by forced expression of telomerase and subsequent spontaneous events leading to loss of p16^INK4a-dependent mechanism generally disrupted neither other normal growth control mechanisms nor affected the ability of the cells to form a differentiated epithelium. In the present study, we have analysed the effect of inhibition of PKD1 expression using siRNA approach in hTert keratinocytes. Transient transfections of cultured keratinocytes with siRNA for PKD1 result in significant reduction of both the level of mRNA of PKD1 and keratinocyte differentiation measured by decreased expression of involucrin and K10. The obtained results suggest prodifferentiative role of PKD1 in these cells which is contrary to its determined role in mouse keratinocytes as a proproliferative and antidifferentiative kinase. One explanation of these differences assumes participation of PKD1 in different transduction pathways in the two cell types.