PSORIASIN BINDS CALCIUM AND IS UP-REGULATED BY CALCIUM TO LEVELS THATRESEMBLE THOSE OBSERVED IN NORMAL SKIN

Recently, we described a small molecular weight protein termed psorias in that showed sequence similarity with the S100 calcium-binding prote ins and that highly upregulated in psoriatic epidermis as well as in p rimary human keratinocytes undergoing abnormal differentiation. Here w e present evidence showing that natural and recombinant psoriasin bind s calcium, as judged by the calcium overlay assay, and that it contain s all the sequence features characteristic of the S100 family. Further more, [S-35]-methionine labeling experiments showed that psoriasin syn thesis is upregulated by 2 mM Ca++ (ratio Ca++/control at 88 h = 2.56) to levels that resemble those observed in unfractionated keratinocyte populations obtained from normal skin.