TRPML1 Promotes Protein Homeostasis in Melanoma Cells by Negatively Regulating MAPK and mTORC1 Signaling
Stacy Y. Kasitinon,
Ugur Eskiocak,
Misty Martin,
Divya Bezwada,
Vishal Khivansara,
Alpaslan Tasdogan,
Zhiyu Zhao,
Thomas Mathews,
Arin B. Aurora,
Sean J. Morrison
Affiliations
Stacy Y. Kasitinon
Children’s Research Institute and Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
Ugur Eskiocak
Children’s Research Institute and Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
Misty Martin
Children’s Research Institute and Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
Divya Bezwada
Children’s Research Institute and Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
Vishal Khivansara
Children’s Research Institute and Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
Alpaslan Tasdogan
Children’s Research Institute and Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
Zhiyu Zhao
Children’s Research Institute and Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
Thomas Mathews
Children’s Research Institute and Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
Arin B. Aurora
Children’s Research Institute and Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
Sean J. Morrison
Children’s Research Institute and Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Corresponding author
Summary: We screen ion channels and transporters throughout the genome to identify those required by human melanoma cells but not by normal human melanocytes. We discover that Mucolipin-1 (MCOLN1), which encodes the lysosomal cation channel TRPML1, is preferentially required for the survival and proliferation of melanoma cells. Loss of MCOLN1/TRPML1 function impairs the growth of patient-derived melanomas in culture and in xenografts but does not affect the growth of human melanocytes. TRPML1 expression and macropinocytosis are elevated in melanoma cells relative to melanocytes. TRPML1 is required in melanoma cells to negatively regulate MAPK pathway and mTORC1 signaling. TRPML1-deficient melanoma cells exhibit decreased survival, proliferation, tumor growth, and macropinocytosis, as well as serine depletion and proteotoxic stress. All of these phenotypes are partially or completely rescued by mTORC1 inhibition. Melanoma cells thus increase TRPML1 expression relative to melanocytes to attenuate MAPK and mTORC1 signaling, to sustain macropinocytosis, and to avoid proteotoxic stress. : Kasitinon et al. conduct an in vivo short hairpin RNA (shRNA) screen of ion channels/transporters and identify TRPML1, a lysosomal cation channel, as preferentially required by melanoma cells. TRPML1 negatively regulates MAPK and mTORC1 signaling to maintain protein homeostasis, to sustain macropinocytosis, and to promote the survival and proliferation of melanoma cells. Keywords: melanoma, TRPML1, MCOLN1, ion channel, MAPK, signaling, mTOR, proteostasis, macropinocytosis
