Phosphoinositide Signaling Regulates Melanogenesis

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DESCRIPTION (provided by applicant): Melanin, a skin pigment that protects the skin and eyes from the harmful effects of UV, is synthesized in a specialized lysosome-related organelle called the melanosome. Melanosome maturation is precisely controlled by the sequential delivery of enzymes that synthesize melanin to the developing organelle such that melanin synthesis only occurs in the stage III or IV melanosome. Defects in melanosome maturation are linked to skin cancer susceptibility and skin pigment variation, highlighting the intrinsic biologial relevance of this pathway. While extensive studies have identified vesicle transport pathways that deliver proteins to the melanosome, little is known about what directs transport vesicles to fuse with the developing melanosome. Recent work from our group has identified specific lipid signals that direct vesicles to fuse with the melanosome. In this application, we hypothesize that phosphoinositide signaling coordinates melanosome maturation with the transcription of enzymes that produce melanin. The studies proposed will: 1) identify lipid signals that direct transport vesicles to the melanosome; 2) identify cellular signals that direct transport vesicles t fuse with autophagosomes or melanosomes; 3) determine how cells coordinate melanosome maturation with the transcription of enzymes that produce melanin and examine the relevance of this pathway in tuberous sclerosis. Completion of the proposed studies will not only enhance our fundamental understanding of how intracellular vesicle transport is coordinated and compartmentalized, but will also lead to the design of pharmacologic agents to stimulate melanosome maturation in skin cancer susceptible patients, reducing the disease burden of the most common type of cancer in the United States.