ENTACTIN-2 - A NEW MEMBER OF BASEMENT-MEMBRANE PROTEIN WITH HIGH HOMOLOGY TO ENTACTIN NIDOGEN/

Using the new signal sequence trap (SST) method, we isolated several c lones encoding secreted and transmembrane proteins from KUSA cells, a murrine osteoblast-like cell line. One isolated novel clone, termed en tactin-2, exhibited a high similarity to mouse entactin/nidogen, a bas ement membrane protein. Although deduction of the amino acid sequence of entactin-2 revealed only 27.4% homology to entactin, many structura l similarities were seen between both proteins. Entactin-2 contains fi ve EGF-like and two thyroglobulin-like motifs, which are both cysteine -rich. Comparison of both proteins clearly revealed that entactin-2 al so contains related domain structures. The rod-like domain of entactin -2, containing the RGD integrin recognition sequence, fused to glutath ione-S transferase (GST), revealed a cell surface-binding activity sim ilar to that of entactin. In addition, the tissue distribution of enta ctin-2 mRNA resembled that of entactin. Furthermore, mRNA expression o f both genes decreased as osteoblastic differentiation progressed. The se results suggest that entactin-2 is a member of the entactin gene fa mily, may have entactin-related functions, and might act as a basement membrane component. : (C) 1998 Academic Press.