ULTRAVIOLET RAYS INDUCED EXPRESSION OF LECTINS ON THE SURFACE OF A SQUAMOUS CARCINOMA KERATINOCYTE CELL-LINE

Human keratinocytic cells from squamous carcinoma (SCL-1) present, und er resting conditions, relatively low amounts of endogenous lectins (s ugar-binding proteins). Upon uv irradiation, they express on their cel l surface large amounts of endogenous lectin molecules able to bind ne oglycoproteins bearing either alpha-L-rhamnosyl or alpha-D-glucosyl re sidues, A similar binding specificity was found with normal human kera tinocytes under the same culture conditions. At sunlike doses, uv.A (3 65 nm) was more efficient than uv.B (312 nm) in the expression of such receptors on the surface of SCL-1 cells, The increased presentation o f lectins by SCL-1 cells was transient and reached a maximum 4 h after irradiation, Such a specific modulation of receptor expression upon u v irradiation might be biologically significant, considering the numer ous intercellular recognition phenomena in skin biology, alpha-L-Rhamn ose-specific receptor on SCL-1 could not be distinguished from alpha-D -glucose-specific receptor on the basis of neoglycoproteins binding, u ptake, and related inhibitions. Lectin expression was mainly detected on the cell. surface, and its overexpression due to uv rays required a de novo protein synthesis process. (C) 1997 Academic Press.