T-COMPLEX-ASSOCIATED EMBRYONIC SURFACE-ANTIGEN HOMOLOGOUS TO MLAMP-1 .1. BIOCHEMICAL AND MOLECULAR ANALYSES

Previously we described an embryonic cell surface glycoprotein, ESGp, associated with the t-embryonic lethal alleles of the mouse t complex. This antigen is expressed on the cell surface of both early mouse emb ryos and embryonal carcinoma (EC) cell lines. The antigen is localized to areas of cell-cell contact in EC lines and redistributes to the ou ter edges of the blastomeres during compaction, thereby indicating a p otential role in embryonic cell-cell interaction. We now report that t his t-complex-associated ESGp is homologous to the mouse lysosomal-ass ociated membrane protein-1 (LAMP-1). Limited protein sequence analyses of the amino terminal and an internal peptide indicate considerable h omology with the LAMP-1 protein. Biochemical parameters such as protei n core size, sulfation and phosphorylation status, and resistance to p roteolysis also demonstrate homology. While we detect only a single me ssage with a mouse LAMP-1 cDNA probe via Northern blotting, Southern a nalyses indicate the existence of at least two homologous LAMP-1 genes . Additionally, we present evidence suggesting that ESGp/LAMP-1 serves as a substrate which may be differentially glycosylated by the activi ties of the gene products of the different t-lethal alleles. (C) 1997 Academic Press.