Figure 3.

Retrograde trafficking in migratory cells, During migration (directionality indicated by thick arrow), the cell exhibits two distinct domains: the retracting rear and the migration front, also known as leading edge. Here again, the Golgi apparatus is localized in a polarized manner such that it directly faces the leading edge. (a) The nonligand-bound integrin α5β1 uses the retrograde route to the Golgi before being re-secreted in a polarized manner to the leading edge. Of note, α5β1 integrin uses both clathrin-dependent and clathrin-independent endocytosis processes. The possible link between retrograde transport and the modality of endocytosis remains unexplored. (b) The matrix metalloproteinase MT1-MMP also follows a similar retrograde transport and polarized secretion cycle. Of note, MT1-MMP expression is regulated by the clathrin-independent cargo CD147, and both are recruited to the same lipid raft nanodomains. Other metalloproteinases such as MMP9 are also found at the leading edge and are positively regulated by Gal3. Altogether, this may suggest a general scheme where adhesion molecules and metalloproteinases cooperate and share similar endocytic and intracellular delivery pathways, further regulated by galectins to facilitate efficient cell migration.