EXPRESSION OF THE NEURAL CELL-ADHESION MOLECULE NCAM BY PEPTIDE-PRODUCING AND STEROID-PRODUCING ENDOCRINE-CELLS AND TUMORS - ALTERNATIVELY SPLICED FORMS AND POLYSIALYLATION

The adhesive properties of neural cell adhesion molecules (NCAMs) can be modified by alternative splicing of the primary transcript or by po sttranslational modifications, such as sialylation. In this article, w e describe distinct forms of alternative splicing and posttranslationa l modification of the extracellular domain of NCAM of various endocrin e tissues and derived tumor cells of the rat and of steroid- and pepti de-hormone producing endocrine cells in humans. NCAM-140 is the major isoform expressed in the rat adrenal gland, adenohypophysis, and in gr anulosa and granulosa-lutein cells. NCAM-180 is predominant in the neu rohypophysis. Polysialylated NCAM is expressed in different endocrine tissues and tumor cells of the rat. Different amounts of NCAM mRNA con taining the ''extra-exon'' VASE at the exon 7/8 splice boundary were d etected in endocrine cells of rats. Human granulosa cells in culture u ndergo luteinization. During this process, the VASE-containing NCAM is oform is supplemented by an alternatively spliced isoform without this insert. Thus, modifications of NCAM may be important for adhesive int eractions in normal and neoplastic endocrine cells. In addition, the d ifferential expression and the alternative splicing of NCAM during lut einization of granulosa cells raise the possibility that NCAM could be involved in folliculogenesis and the formation of the corpus luteum i n humans.