When substances are produced in one cell, yet required in another, they have to travel long distances in a tissue. So far, common science has not been able to adequately explain this process. Now, MPI-CBG researchers of the groups of Suzanne Eaton and Christoph Thiele have discovered so-called argosomes: Like trucks, they are able to pick up proteins and transport them from one cell to the other within a tissue. Wnt and Hedgehog family proteins are secreted signalling molecules (morphogens) that act at both long and short range to control growth and patterning during development. Both proteins are covalently modified by lipid, and the mechanism by which such
hydrophobic molecules might spread over long distances is unknown. The Dresden labs could show that Wingless, Hedgehog and gpi-linked proteins copurify with lipoprotein particles, and co-localize with them in the developing wing epithelium of Drosophila. In larvae with reduced lipoprotein levels, Hedgehog accumulates near its site of production, and fails to signal over its
normal range. Similarly, the range of Wingless signalling is narrowed. Thus, a novel function for lipoprotein particles has been characterised: they act as vehicles for the movement of lipid-linked morphogens and gpi-linked proteins.