Molecular mechanisms of pigment transport in melanophores

We present an overview of the research on intracellular transport in pigmen t cells, with emphasis on the most recent discoveries. Pigment cells of low er vertebrates have been traditionally used as a model for studies of intra cellular transport mechanisms, because these cells transport pigment organe lles to the center or to the periphery of the cell in a highly co-ordinated fashion. It is now well established that both aggregation and dispersion o f pigment in melanophores require two elements of the cytoskeleton: microtu bules and actin filaments. Melanosomes are moved along these cytoskeletal t racks by motor proteins. Recent studies have identified the motors responsi ble for pigment dispersion and aggregation in melanophores, We propose a mo del for the possible roles of the two cytoskeletal transport systems and ho w they might interact. We also discuss the putative mechanisms of regulatio n of pigment transport, especially phosphorylation, Last, we suggest areas of research that will receive attention in the future in order to elucidate the mechanisms of organelle transport.