Characterization of the expression and function of N-methyl-D-aspartate receptor in keratinocytes.

The N-methyl-D-aspartate (NMDA) receptor is expressed on neural tissue where it gates calcium ion entry upon stimulation. Using immunohistochemistry, it has been demonstrated in this study that the NMDAR1 receptor is also expressed on keratinocytes (KCs) in normal human skin and inflamed psoriatic skin in vivo. Furthermore, the NMDA receptor was functional as demonstrated by the ability of this receptor to trigger Ca++ influx in KCs. Incubation of cultured, human KCs with MK-801 decreases the cell growth and induces an increase in apoptosis. These findings demonstrate that the KC expression of NMDA receptor is a mechanism through which the influx of Ca++ into the cell can be regulated and suggest that the expression of this receptor may play a role in the regulation of KC growth and differentiation.