PROMOTION OF CELL-ADHESION BY SINGLE-STRANDED AND TRIPLE-HELICAL PEPTIDE MODELS OF BASEMENT-MEMBRANE COLLAGEN ALPHA-1(IV)531-543 - EVIDENCEFOR CONFORMATIONALLY DEPENDENT AND CONFORMATIONALLY INDEPENDENT TYPE-IV COLLAGEN CELL-ADHESION SITES

Several regions within the triple-helical domain of type IV collagen f unction as cellular recognition sites. We have demonstrated previously that melanoma cell activities promoted by the alpha 1(IV)1263-1277 se quence are enhanced by triple helicity (Fields, C. G., Mickelson, D. J ., Drake, S. L., McCarthy, J. B., and Fields, G. B. (1993) J. Biol. Ch em. 268, 14153-14160), whereas Eble et al. reached similar conclusions for alpha 1 beta 1 integrin-mediated fibrosarcoma cell adhesion to [a lpha 1(IV)](2) alpha(2)(IV)434-472 (Eble, J. A., Golbik, R., Mann, K., and Kuhn, K. (1993) EMBO J. 12, 4795-4802). In the present study, we have examined the cell adhesion activities of a third region in type I V collagen. A single-stranded peptide (SSP) incorporating the alpha 1( IV)531-543 sequence promoted the adhesion of melanoma, ovarian carcino ma, and Jurkat cells in a dose-dependent manner, with 40% cell adhesio n observed at [SSP] = 1.8, 11.5, and 42.2 mu M, respectively. Nearly i dentical results were obtained for cell adhesion to an all-D-enantiome r of the SSP, suggesting that the cell surface receptor(s) for this si te do not discriminate based on chirality. The alpha 1(IV)531-543 sequ ence maintained its cell adhesion promoting activity when incorporated into a homotrimeric triple-helical polypeptide, although relative lev els of adhesion were either slightly enhanced or slightly diminished c ompared with the SSP. Triple-helical conformation was thus not critica l for cellular recognition of the alpha 1(IV)531-543 sequence. Single- site substitution experiments of the SSP showed no overall correlation between the biological effects of substitutions and SSP conformation. The SSP, D-SSP, triple-helical polypeptide, and SSP substitution resu lts suggest that cell recognition of the alpha 1(IV)531-543 sequence i s generally independent of substrate conformation. The present and pri or studies indicate that ''conformationally dependent'' and ''conforma tionally independent'' cellular recognition sites exist within the tri ple helical domain of type IV collagen.