P38 MAPK Promotes Migration and Metastatic Activity of BRAF Mutant Melanoma Cells by Inducing Degradation of PMCA4b.

Metastatic melanoma is the most aggressive type of skin cancer. Previously, we identified the plasma membrane Ca2+ pump isoform 4b (PMCA4b or ATP2B4) as a putative metastasis suppressor in BRAF mutant melanoma cells. Metastasis suppressors are often downregulated in cancer, therefore, it is important to identify the pathways involved in their degradation. Here, we studied the role of p38 MAPK in PMCA4b degradation and its effect on melanoma metastasis. We found that activation of p38 MAPK induces internalization and subsequent degradation of PMCA4b through the endo/lysosomal system that contributes to the low PMCA4b steady-state protein level of BRAF mutant melanoma cells. Moreover, BRAF wild type cell models including a doxycycline-inducible HEK cell system revealed that p38 MAPK is a universal modulator of PMCA4b endocytosis. Inhibition of the p38 MAPK pathway markedly reduced migration, colony formation and metastatic activity of BRAF mutant cells in vitro partially through an increase in PMCA4b and a decrease in beta 4 integrin abundance. In conclusion, our data suggest that the p38 MAPK pathway plays a key role in PMCA4b degradation and inhibition of this pathway-by increasing the stability of PMCA4b-may provide a potential therapeutic target for inhibition of melanoma progression and metastasis.