Melanosomes are specialized lysosomes that store pigment for eventual release by
ID: 204208 • Letter: M
Question
Melanosomes are specialized lysosomes that store pigment for eventual release by exocytosis. Various cells such as skin and hair cells then take up the pigment, which accounts for their characteristic pigmentation. Mouse mutants that have defective melanosomes often have pale or unusual coat colors. One such light-colored mouse, the Mochamouse, has a defect in the gene for one of the subunits of the adaptor protein complex AP3, which is associated with coated vesicles budding from the TGN. How might the loss of adaptor protein complexes function cause a defect in melanosomes?
Explanation / Answer
Melanosomes are the organelle present in the animal cells. These are the sites for storage, synthesis and melanin transport. Melanosomes are the light absorbing pigments. These are responsible for the photoprotection and color in the cells and tissues of the animal.
The incorporation of the specific cargo proteins into the clathrin coated vesicles by the linking the clatherin coat to specific cargo receptors is mediated by the adaptor proteins. Melanosomes are the specialized lysosomes, it would seem reasonable that the defect in AP3 affects the pathway for the delivery of pigment granule from the trans Golgi network, which involves clathrin coated vesicles. AP3 lacalized to coated vesicles budding from the trans Golgi network, and are involved in the transport from the Golgi to lysosomes.