LaNt α31 modulates LM332 organisation during matrix deposition leading to cell-matrix adhesion and migration defects.

The laminin N terminus (LaNt) proteins are a family of laminin and netrin related proteins derived by alternative splicing from laminin encoding genes. There are few reports to date on LaNt protein function. However, one family member, LaNt α31, has been shown to regulate epidermal keratinocyte migration and adhesion, although the mechanism for these effects is unknown. Based on its protein architecture, we predicted that LaNt α31 would influence laminin organisation. To test this prediction, we induced expression of GFP tagged LaNt α31 via adenoviral delivery into human epidermal and corneal keratinocytes. Consistent with the LaNt/laminin interaction hypothesis, LaNt α31 GFP co-distributed with laminin α3 in the extracellular matrix and formed a complex together as indicated by co-immunoprecipitation, while live cell assays revealed the proteins to be deposited together during new matrix synthesis. Moreover, the induced expression of LaNt α31 led to changes to laminin β3 organisation into tight clusters compared with wide arcs in control cells. These changes were associated with early maturation of hemidesmosomes and mislocalization of focal adhesion complexes. At the cellular level, epithelial cells expressing LaNt α31 GFP displayed decreased scratch closure and single cell motility rates and increased cell spread area. These differences were rescued through the provision of a pre-formed cell-derived matrix. Together these data identify a new mechanism that influences the early stages of laminin matrix assembly and adds the LaNt proteins as new players in defining cell-to-matrix adhesion and migration characteristics.