Adhesion mediated by fibronectin's alternatively spliced ED(b) (EIIIB) and its neighboring type III repeats

Adhesion functions of cellular fibronectin's (FN) alternatively spliced ED(b) (EIIIB) domain, as well as its neighboring type III repeats III7 and III8, were investigated with several cultured murine and human cell types. Minigene constructs encoding various permutations of these repeats and expressed in bacteria were used as shown previously in function studies of ED(a) and its neighboring repeats (P. Xia and L. A. Gulp Exp. Cell Res. 213, 253-265, 1994). When substrata of recombinant proteins were incubated with several fibroblastic or neuronal derivative cell. lines, cell attachment responses varied widely in a cell-type-specific manner. Balb/c 3T3 cells were shown to adhere to recombinant protein substrata in dose-dependent and EDTA-sensitive manners. Responses also varied with which repeat combinations were being tested, from excellent (Balb/c 3T3, src-3T3), to intermediate (Platt cells), to poor (LZEJ, VA-13, and F11), with ED(b)(+)-containing proteins generally giving better adhesion than ED(b)(-) proteins. On select recombinant proteins, cells showed limited cytoplasmic spreading (3T3 and src-3T3) or neurite extension (Platt and F11), while other cell lines (VA-13 and LZEJ) did not show any morphological changes beyond attachment. Again, ED(b)(+)-containing recombinants were more effective at inducing these morphological changes than the neighboring repeats. These results demonstrate that the ED(b) domain of cellular FNs and its neighboring type III homology repeats contain important adhesion-promoting sequences, which may be regulated by cells through alternative splicing of FN's primary transcript. (C) 1996 Academic Press, Inc.