Probing the function of melanosomal transporters in pigmentation using metabolic profiling

Beneficiary: David M. Sabatini, Whitehead Institute of Biomedical Research

Grant: 1.278.270 DKK

Studies in human populations have identified dozens of pigmentation genes, many of which encode proteins with well-understood functions, such as in melanocyte development, melanin biosynthesis, and the biogenesis and trafficking of specialized melanin-containing organelles called melanosomes.

Yet, there are other pigmentation genes that we know much less about, such as those that encode putative transporter proteins on the melanosome surface. These putative melanosomal transporters have been reported to import precursor metabolites for melanin synthesis or regulate melanosomal pH; however, many of these findings have been controversial or speculative. Deciphering the molecular function of these putative transporters and their physiological substrates is crucial to our understanding of pigmentation.

To address this problem, we propose to determine the metabolite composition of melanosomes and define the role of individual transporters in melanosomal function. We will develop a purification method to rapidly isolate intact melanosomes and analyse them by liquid chromatography and mass spectrometry to compile the first catalog of melanosomal metabolites. We will subsequently characterize SLC45A2, a putative melanosomal transporter that modulates human pigmentation in response to sunlight. By comparing the metabolite profile of wild-type versus SLC45A2-deficient melanosomes, we will identify candidate SLC45A2 substrates and validate them using biochemical assays, a workflow that will be applied to other putative melanosomal transporters.

This study will present the first detailed analysis of melanosome metabolites, as well as identify key metabolites and their transporters essential for melanogenesis. This work could inform new ways to modulate pigmentation and treat pigmentation pathologies.