NESS - Renalase Inhibition Induces Melanogenesis Via MAPK and PI3K/AKT Signaling Pathways

Back to 2016 Annual Meeting

Renalase Inhibition Induces Melanogenesis Via MAPK and PI3K/AKT Signaling Pathways
*Lindsay Hollander¹^,2^,3, *Xiaojia Guo¹^,3, *Robert Safirstein¹^,3, *Gary Desir¹^,3, Charles Cha¹^,3
¹Yale University, New Haven, CT;²University of Connecticut, Farmington, CT;³VACHS, West Haven, CT

Objective: Renalase (RNLS) is a secreted flavoprotein we have previously demonstrated to promote the growth and progression of melanoma via signaling through the PI3K/AKT and MAPK pathways. The same pathways are vital to the melanocyte’s ability to regulate melanogenesis. Activation of ERK1/2 phosphorylates microphthalmia transcription factor (MITF) at serine 73, which leads to MITF ubiquitination and degradation. p38 activation leads to MITF activation and increased tyrosinase (Tyr) expression. PI3K/AKT inhibition leads to GSK3β activation and MITF phosphorylation at serine 289, which facilitates its binding to the M-box of the Tyr promoter. We tested the hypothesis that RNLS could downregulate melanogenesis by examining the effect of RNLS inhibition on melanin production. Design: Lentiviral particles were used to transduce and stably knockdown RNLS expression in B16-F10 melanoma cells. Intra- and extracellular melanin contents were compared via 475nm absorbance measurements following dissolution in 1N NaOH. Cell lysate mRNA and protein were evaluated with qRT-PCR and western blots to illustrate the involved pathways. Results: Inhibition of RNLS signaling significantly enhanced the melanogenesis of the melanoma cells. Intracellular melanin content increased 2.2-fold (p<0.001), and extracellular melanin content increased 2.0-fold (p<0.001) when RNLS expression was blocked. MITF gene expression was increased 2.6-fold (p=0.003) with the knockdown of RNLS. Western blot analysis demonstrated decreased ERK1/2 and PI3K/AKT activation and increased p38 activation, as well as increased expression of Tyr, tyrosinase-related protein 1 (TRP1), and tyrosinase-related protein 2 (TRP2) in the absence of RNLS. Conclusions: These results further validate that RNLS acts through the PI3K/AKT and MAPK signaling pathways in melanoma. Inhibition of RNLS signaling through these pathways leads to increased expression of MITF, Tyr, TRP1, and TRP2 and downstream increased cellular melanogenesis.

Back to 2016 Annual Meeting