Endolysosomal transient receptor potential mucolipins and two-pore channels: implications for cancer immunity.

Past research has identified that cancer cells sustain several cancer hallmarks by impairing function of the endolysosomal system (ES). Thus, maintaining the functional integrity of endolysosomes is crucial, which heavily relies on two key protein families: soluble hydrolases and endolysosomal membrane proteins. Particularly members of the TPC (two-pore channel) and TRPML (transient receptor potential mucolipins) families have emerged as essential regulators of ES function as a potential target in cancer therapy. Targeting TPCs and TRPMLs has demonstrated significant impact on multiple cancer hallmarks, including proliferation, growth, migration, and angiogenesis both in vitro and in vivo. Notably, endosomes and lysosomes also actively participate in various immune regulatory mechanisms, such as phagocytosis, antigen presentation, and the release of proinflammatory mediators. Yet, knowledge about the role of TPCs and TRPMLs in immunity is scarce. This prompts a discussion regarding the potential role of endolysosomal ion channels in aiding cancers to evade immune surveillance and destruction. Specifically, understanding the interplay between endolysosomal ion channels and cancer immunity becomes crucial. Our review aims to comprehensively explore the current knowledge surrounding the roles of TPCs and TRPMLs in immunity, whilst emphasizing the critical need to elucidate their specific contributions to cancer immunity by pointing out current research gaps that should be addressed.

Endolysosomal TRPML1 channel regulates cancer cell migration by altering intracellular trafficking of E-cadherin and ß1-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 antimigratory 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 polymerization, and intracellular trafficking of two promigratory proteins: E-cadherin and ß1-integrin. Interestingly, KO of TRPML1 differentially interferes with the recycling process of E-cadherin and ß1-integrin in a cell line-dependant manner, while 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 ß-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.