Endolysosomal TRPML1 channel regulates cancer cell migration by altering intracellular trafficking of E-cadherin and β1-integrin

Metastasis still accounts for 90 % of all cancer related death cases. An increase of cellular mobility and invasive traits of cancer cells mark two crucial prerequisites of metastasis. Recent studies highlight the involvement of the endolysosomal cation channel TRPML1 in cell migration. Our results identified a widely anti-migratory effect upon loss of TRPML1 function in a panel of cell lines in vitro and reduced dissemination in vivo. As mode-of-action, we established TRPML1 as a crucial regulator of cytosolic calcium levels, actin polymerisation and intracellular trafficking of two pro-migratory proteins: E-cadherin and β1-integrin. Interestingly, knockout (KO) of TRPML1 differentially interferes with the recycling process of E-cadherin and β1-integrin in a cell line dependant manner, whilst resulting in the same phenotype of decreased migratory and adhesive capacities in vitro. Additionally, we observed a coherence between reduction of E-cadherin levels at membrane site and phosphorylation of NF-κB in a β-catenin/p38-mediated manner. As a result, an E-cadherin/ NF-κB feedback loop is generated regulating E-cadherin expression on a transcriptional level. Consequently, our findings highlight the role of TRPML1 as a regulator in migratory processes and suggest the ion channel as a suitable target for the inhibition of migration and invasion.