Fig. 7. Internalised MT1-MMP colocalised with caveolin-1 and clathrin heavy chain and is present in caveolin-1 containing fractions. bbHT1080 cells, which had internalised IgG-bound MT1-MMP complexes for 10 minutes (A,D), were fixed, permeabilised and incubated with antibodies directed against caveolin-1 (B) and clathrin heavy chain (E) followed by a fluorescently labelled secondary antibody. Merged panels (C,F) are shown in the right-hand column. Arrowheads are examples of colocalising structures. Bar, 20 µm. (G) After a detergent-free carbonate-based extraction, HT1080 cells were homogenised and subjected to subcellular fractionation. Fractions (1 ml) were collected from the top of the gradient, separated on a 10% SDS-PAGE gel and immunoblotted using anti-MT1-MMP affinity-purified IgG (upper panel) or with an anti-caveolin-1 pAb (lower panel).