Wnt Signal Production, Secretion, and Diffusion

This chapter briefly discusses the lipid and sugar modification of Wnt proteins and focuses on the specialized secretion machinery that mediates the release of Wnt from producing cells and the mechanisms that facilitate and control the spreading of Wnt in morphogen gradient formation. Wnts undergo two major types of posttranslational modification, N-glycosylation and lipidation. Lipoprotein particles act as lipid carriers and are therefore ideally suited to facilitate diffusion of Wg and Hh, which may bind to the particles through insertion of their fatty acid and cholesterol tails into the lipid core. Accumulating evidence suggests that packing of Wnts in specialized carriers is necessary for their long-range transport in extracellular space.