Nicein/kalinin is an epithelium-specific adhesion molecule involved in maintaining dermo-epidermal cohesion and promoting attachment of keratinocytes (Rousselle et al. 1991; Verrando et al. 199 I). The protein co-localizes with the hemidesmosomal filaments connecting the epidermal basal cells to the anchoring fibrils network of papillary dermis (Rousselle et al. 1991;Verrando et al. 1987). Nicein was first purified from keratinocyte-conditioned medium and proved to be a heterotrimer comprising disulfidelinked subunits of 100, 125, and 150 kDa (Verrando et al. 1987). Sequence analysis revealed that each subunit is unique and that homologies exist between nicein and human laminin (Baudoin et al. 1994;Gerecke et al. 1994; Vailly et al. 1994a).
Laminin is a major non-collagenous component involved in cell attachment, spreading, growth, and differentiation. This cross-shaped molecule consists of a heavy A chain (400 kDa) and two light B 1 and B2 chains (-200 kDa each;Engel 1992). Laminin chains restricted to basement membranes of specific tissues have been recently identified S-laminin, homologous to the B 1 chain, is detected in the synaptic sites of muscles, in peripheral nerves, and in kidney blood vessels and glomeruli (Hunter et al. 1989). Merosin and K-laminin are homologous to the chain A. Merosin is found in striated muscles and peripheral nerves (Ehrig et al. 1990). K-laminin is limited to the dertoo-epidermal junction of the skin (Marinkovich et al. 1992). It is likely that nicein constitutes a new isoform of laminin, since the 100-kDa subunit of nicein is homologous to the laminin B2 chain (Vailly et al. 1994a), the 125-kDa subunit of nicein is homologous to the laminin B 1 chain (Gerecke et al. 1994), and the 150-kDa subunit of nicein is weakly homologous to the laminin A chain (Baudoin et al. 1994). Nicein and laminin are immunologically distinct
The nucleotide sequence data reported in this paper have been submitted to GenBank (accession numbers: L20476, L20477, and L20478).