3. The Evolution, Structure, and Trafficking of Pigment Organelles
We have discovered a novel Perilipin protein that is exclusively conserved in bony fishes, like zebrafish, goldfish, and tilapia. Perilipins are an ancient family of proteins that are involved in regulating lipid metabolism in higher vertebrates, including humans. They are embeded into the single membrane of lipid droplets (which are filled with tryglicerides) and regulate their trafficking, usage, and storage. Interestingly, we have discovered that the novel Perilipin in fish is embedded into carotenoid droplets, which are full of a lipophilic yellow/gold pigment called carotenoid. Our work suggests that the carotenoid droplet in a pigment cell is analogous to a lipid droplet in a fat cell and, critically, uses the same family of proteins to regulate intracellular trafficking. We are currently testing the functional role of this novel Perilipin in pigment aggregation and dispersion within the pigment cell.
Carotenoid pigment aggregation and dispersion in adult zebrafish xanthophores. A. Drawing of carotenoid pigment storage in carotenoid droplets (CD), which are substructures of the carotenoid body (CB), a structure analogous to the smooth endoplasmic reticulum. B. Drawing of a xanthophore with CD aggregation (left) and following PKA activation (right). Arrows indicated the perinuclear aggregation of the CB (left) and subsequent dispersion (right) following PKA activation.