FIGURE 4.

Clustering of syndecan-4 bearing one or no heparan sulfate chains, with antibodies triggers incorporation of αSMA into stress fibers. A–L, syndecan-4-null mouse fibroblasts were transfected with the syndecan-4 cDNAs encoding none or one GAG attachment site. Transfected cells were grown in the presence of serum for 24 h prior to serum starvation for 24 h. Syndecan-4 clustering was achieved with a polyclonal anti-syndecan-4 antibody raised against an N-terminal peptide sequence, followed by an Alexafluor-568 conjugated anti-chicken IgY. Transfected cells were identified by GFP from the bicistronic vector, cell surface syndecan-4 visualized directly, and the αSMA detected by an Alexafluor 405 antibody (blue). M, percentage of transfected cells with αSMA incorporated into stress fibers was calculated in syndecan-4-expressing cells that had been clustered as above (black bars) or remained untreated (light gray bars). n = 110–130 cells from each condition. The scale bar is 10 μm.