LAMININ AND HEPARAN-SULFATE PROTEOGLYCAN MEDIATE EPITHELIAL-CELL POLARIZATION IN ORGANOTYPIC CULTURES OF EMBRYONIC LUNG-CELLS - EVIDENCE IMPLICATING INVOLVEMENT OF THE INNER GLOBULAR REGION OF LAMININ BETA-1 CHAIN AND THE HEPARAN-SULFATE GROUPS OF HEPARAN-SULFATE PROTEOGLYCAN

The extracellular matrix and in particular the basement membrane (BM) play an important role in the induction of organotypic rearrangement o f cells in culture. This process involves cell aggregation, sorting in to epithelial and mesenchymal components, epithelial cell polarization , and lumen formation. In this study, a combination of laminin (LM) an d heparan sulfate proteoglycan (HSPG), two major BM constituents, indu ced organotypic rearrangement of embryonic mouse lung cells. In the ab sence of LM/HSPG supplementation, the cells sorted into epithelial and mesenchymal compartments but epithelial cell polarization and lumen f ormation did not occur. Neither LM, nor HSPG alone could trigger this process. Synthetic peptide F-9, representing an amino acid sequence fr om the inner globular region of the laminin beta 1 chain (RYVVLPRPVCFE KGMNYTVR) induced organotypic cell rearrangement when substituted for LM. Exogenous LM as well as peptide F-9 were localized at the epitheli al-mesenchymal interface of organotypic cultures, where a BM-like stru cture is formed de novo. Organotypic cell rearrangement was blocked by heparin, heparan sulfate, or antibodies against peptide F-9. Binding assays indicated that peptide F-9 interacts with HSPG but not with LM or type IV collagen. Preincubation of embryonic lung cells with peptid e F-9 resulted in a significant increase in cell attachment to HSPG bu t not to other major BM constituents. These findings suggest that the interaction between LM and BM HSPG is critical for the development of epithelial cell polarization and lumen formation. This interaction occ urs at the epithelial-mesenchymal interface and is mediated by a site in the LM molecule represented by peptide F-9 and the heparan sulfate groups of HSPG. (C) 1996 Academic Press, Inc.