The molecular machinery for the biogenesis of lysosome-related organelles: lessons from Hermansky-Pudlak syndrome.

Hermansky-Pudlak syndrome (HPS) defines a group of autosomal recessive disorders characterized by defects in lysosome-related organelles such as melanosomes and platelet dense granules. The genes that are defective in each of the different forms of HPS in humans, or in HPS-like disorders in mice, are thought to encode components of a putative molecular machinery required for the formation of specialized organelles of the lysosomal system. This review discusses the biochemical and functional properties of the products of identified HPS genes, which include subunits of the AP-3 complex and the novel proteins HPS1p, HPS3p, HPS4p, pallidin and muted.