Cyclic AMP promotes a peripheral distribution of melanosomes and stimulates melanophilin/Slac2-a and actin association

SPECIFIC AIMSThe aim of the present study was to investigate the possible regulation of melanosome transport in mammalian melanocytes by α-MSH, a physiologic melanocyte-differentiating agent that stimulates the cyclic AMP (cAMP) pathway. We studied, at the molecular level, the effect of the activation of the cAMP pathway on proteins involved in the control of melanosome transport.PRINCIPAL FINDINGS1. cAMP induces rapid melanosome docking at the cell periphery: role of the actin networkUsing time-lapse video microscopy, we observed in basal conditions a bi-directional movement of melanosomes with no change in melanosome repartition after 70 min (Fig. 1⤻ A). We added forskolin (20 μM) and observed the same cell an additional 100 min (Fig. 1B⤻ , movie 1). As early as 14 min after forskolin addition, we noted that melanosomes started to gather at the extremities of dendrite outgrowths. This was more obvious after longer exposure to forskolin. αMSH, a physiological cAMP-elevating agent, also induced melanosome...