Lysosomal TRPML1 regulates mitochondrial function in hepatocellular carcinoma cells

Abstract

Liver cancers, including hepatocellular carcinoma (HCC), are the second most lethal cancers worldwide and novel therapeutic strategies are still highly needed. Recently, the endolysosomal cation channel TRPML1 has gained focus in cancer research representing an interesting novel target. We utilized the recently developed isoform-selective TRPML1 activator ML1-SA1 and the CRISPR/Cas9 system to generate tools for over-activation and loss-of-function studies on TRPML1 in HCC. After verification of our tools, we investigated the role of TRPML1 in HCC by studying proliferation, apoptosis, and proteomic alterations. Further, we analyzed mitochondrial function in detail, facilitating confocal and transmission electron microscopy, combined with SeahorseTM and Oroboros® functional analysis. We report that TRPML1 over-activation by a novel, isoform-selective, low-molecular activator induces apoptosis by impairing mitochondrial function calcium dependently. Additionally, TRPML1 loss-of-function deregulates mitochondrial renewal, which leads to proliferation impairment. Thus, our study reveals a novel role for TRPML1 as regulator of mitochondrial function and its modulators as promising molecules for novel therapeutic options in HCC therapy.

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

“…For RIL-175 and B16F10-luc ( Fig. S1 , E and F ) cells we performed a KO of TRPML1 using the CRISPR/Cas9 system, as previously reported ( 32 , 34 ).…”

“…Recently endolysosomal cation channels have emerged as an attractive anticancer target: namely the mucolipin subfamily of transient potential receptors (TRPMLs), which comprises three isoforms—TRPML1 (MCOLN1), TRPML2 (MCOLN2), and TRPML3 (MCOLN3) ( 31 ). TRPML1, the most intensively researched member of the family, is ubiquitously expressed in the membranes of endosomes and lysosomes, whereas TRPML2 and TRPML3 are mainly localized in specialized cells ( e.g., immune cells, hair cells of the inner ear, secretory cells, and melanocytes) ( 32 , 33 ). In past research TRPML1 has been linked to ion homeostasis, vesicular trafficking, and autophagy ( 34 , 35 ).…”

New Players in Neuronal Iron Homeostasis: Insights from CRISPRi Studies

“…The cation channel MCOLN1 (also known as TRPML1) was initially identified as an iron efflux channel from the endolysosomal system, and MCOLN1-deficient cells shows reduced cytoplasmic Fe 2+ levels concomitant with endolysosomal iron retention [ 75 ]. MCOLN1 KO triggers lysosomal dysfunction, disturbed autophagy, and reduced mitochondrial renewal by mitophagy [ 76 ]. CRISPRi of MCOLN1 in neuronal cells replicates the previously observed lysosomal iron retention phenotype.…”

Magnetic modulation of lysosomes for cancer therapy

“…Lysosomes are one of the most important calcium storage of cells, with a concentration ranging from 0.2 to 0.6 mM, compared to 0.1 nM in the cytoplasm (Bagur & Hajnoczky, 2017; Pihan et al, 2022). Calcium signaling regulates important functions of lysosomes, such as biogenesis, exocytosis, and lysosomal fusion with other vesicles (Otsu et al, 2020; Siow et al, 2022). However, as an important intracellular signal, most studies on calcium are limited to the endoplasmic reticulum and mitochondria.…”