Division of labor of Schwann cell integrins during migration on peripheral nerve extracellular matrix ligands.

Myelination of the peripheral nervous system (PNS) requires the migration of Schwann cells during both development and regeneration. We have characterized the expression pattern of Schwann cell integrins and analyzed their role in migration on different ECM substrates known to be present within the PNS. We found that Schwann cells in cell culture express four beta1 integrins, alpha1 beta1, alpha2 beta1, alpha6 beta1, and another unidentified beta1 integrin, as well as two alpha v integrins, alpha v beta3 and alpha v beta8. Using the Varani migration assay, we found that laminin-1, laminin-2 (merosin), and fibronectin increased Schwann cell migration, while vitronectin and collagen did not increase migration compared to an uncoated plastic substrate. Schwann cell migration on laminin-1 and laminin-2 (merosin) was blocked by antibodies against beta1 integrins, but not affected by RGD peptides or antibodies against beta3 integrins. In contrast, migration on fibronectin was unaffected by antibodies against beta1 and beta3 integrins but was blocked by RGD peptides. This in vitro study shows that there is a division of labor of Schwann cell integrins in the regulation of migration on peripheral nerve ECM components; beta1 integrins mediate migration on laminin-1 and laminin-2 (merosin), while alpha v integrins mediate migration on fibronectin. Taken together, these results suggest that multiple interactions between Schwann cell integrins and ECM within the PNS will contribute to Schwann cell migration during myelination of the PNS.