GALECTIN-7, A HUMAN 14-KDA S-LECTIN, SPECIFICALLY EXPRESSED IN KERATINOCYTES AND SENSITIVE TO RETINOIC ACID

A cDNA encoding a novel member of the S-lectin family has been cloned from human epidermis, The 14-kDa protein of pI 7 predicted by the 136- amino-acid open reading frame of the sequence was called galectin-7 ac cording to the presently accepted nomenclature. A GST fusion protein a uthentified the lactose-binding properties expected for a member of th is lectin subfamily. Galectin-7 was identified on two-dimensional gels of keratinocyte protein extracts. Differential and in situ hybridizat ions indicate that this lectin is specifically expressed in keratinocy tes. It is expressed at all stages of epidermal differentiation (i.e., in basal and suprabasal layers). It is moderately repressed by retino ic acid, a behavior contrasting with those of other keratinocyte marke rs sensitive to this agent, which, either basal, are induced, or supra basal, are repressed. This effect of retinoic acid on a keratinocyte c ell type marker such as galectin-7 is more reminiscent of its metaplas iogenic effect in vivo than of its inhibitory effect on terminal epide rmal differentiation in vitro. This interpretation is supported by the fact that in chick epidermis a 14-kDa S-lectin is suppressed during r etinoic acid-induced mucous metaplasia. (C) 1995 Academic Press, Inc.