CHARACTERIZATION OF THE ROLE OF STIM1 IN MELANOGENESIS

Intracellular Ca2+ homeostasis plays a key role in the control of melanogenesis, the process responsible for the biogenesis of melanosomes, and for melanin accumulation. Ca2+ homeostasis is maintained by several mechanisms, including subcellular compartmentalization and protein pumps and channels. Among the different organelles involved in the control of intracellular Ca2+ concentrations, the endoplasmic reticulum (ER) is essential. In this paper the authors focus their attention on the transmembrane protein Stromal Interaction Molecule 1 (STIM1), which is located at the ER and that is important for Ca2+ handling. They suggest that STIM1 regulate melanogenesis upon UV exposure. The authors characterize the molecular events and factors that control STIM1 expression during melanogenesis. Specifically, they show that STIM1 expression is fostered by αMSH (melanocyte α-stimulating hormone). The stimulation by αMSH induces the cAMP-PKA-CREB-MITF signaling pathway: this evidence prompted the authors to hypothesize that STIM1 expression could dependend on the microphthalmia-associated transcriptional factor (MITF). Some studies have pointed out that overexpression of MITF leads to an increased expression of STIM1, while STIM1 levels decrease after silencing of MITF. The role of STIM1 in melanogenesis is still understudied, and in this paper the authors will try to fill this knowledge gap.