Figure 5.

Laminin polymer bonds are required for network formation on the cell surface. Laminins were treated with reagents that block laminin polymerization, but not cell adhesion activities. Myotubes were incubated with these polymer-deficient laminins for 1 h at 1 μg/ml (top) or for 4 h at 10 μg/ml (bottom) then evaluated for the presence of laminin aggregates. In the presence of short arm fragments E1′ and E4, laminin was unable to organize into reticular clusters in 1 h (untreated laminin shown at left). Similarly, AEBSF-treated laminin (Fig. 4) did not reorganize on the cell surface into aggregates. Formation of ordered laminin networks (at 4 h) was also blocked by polymer-disrupting reagents E1′ and AEBSF. Bar, 5 μm.