p62/SQSTM1 Cooperates with Hyperactive mTORC1 to Regulate Glutathione Production, Maintain Mitochondrial Integrity, and Promote Tumorigenesis.

Abstract

p62/sequestosome-1 (SQSTM1) is a multifunctional adaptor protein and autophagic substrate that accumulates in cells with hyperactive mTORC1, such as kidney cells with mutations in the tumor suppressor genes tuberous sclerosis complex (TSC)1 or TSC2. Here we report that p62 is a critical mediator of TSC2-driven tumorigenesis, as Tsc2+/- and Tsc2f/f Ksp-CreERT2+ mice crossed to p62-/- mice were protected from renal tumor development. Metabolic profiling revealed that depletion of p62 in Tsc2-null cells decreased intracellular glutamine, glutamate, and glutathione (GSH). p62 positively regulated the glutamine transporter Slc1a5 and increased glutamine uptake in Tsc2-null cells. We also observed p62-dependent changes in Gcl, Gsr, Nqo1, and Srxn1, which were decreased by p62 attenuation and implicated in GSH production and utilization. p62 attenuation altered mitochondrial morphology, reduced mitochondrial membrane polarization and maximal respiration, and increased mitochondrial reactive oxygen species and mitophagy marker PINK1. These mitochondrial phenotypes were rescued by addition of exogenous GSH and overexpression of Sod2, which suppressed indices of mitochondrial damage and promoted growth of Tsc2-null cells. Finally, p62 depletion sensitized Tsc2-null cells to both oxidative stress and direct inhibition of GSH biosynthesis by buthionine sulfoximine. Our findings show how p62 helps maintain intracellular pools of GSH needed to limit mitochondrial dysfunction in tumor cells with elevated mTORC1, highlighting p62 and redox homeostasis as nodal vulnerabilities for therapeutic targeting in these tumors. Cancer Res; 77(12); 3255-67. ©2017 AACR.

• Authors: Hilaire C Lam, Christian V Baglini, Alicia Llorente Lope, Andrey A Parkhitko, Heng-Jia Liu, Nicola Alesi, Izabela A Malinowska, Darius Ebrahimi-Fakhari, Afshin Saffari, Jane J Yu, Ana Pereira, Damir Khabibullin, Barbara Ogorek, Julie Nijmeh, Taylor Kavanagh, Adam Handen, Stephen Y Chan, John M Asara, William M Oldham, Maria T Diaz-Meco, Jorge Moscat, Mustafa Sahin, Carmen Priolo, Elizabeth P Henske
• Journal: Cancer research (Cancer Res) Vol. 77 Issue 12 Pg. 3255-3267 (06 15 2017) ISSN: 1538-7445 [Electronic] United States
• PMID: 28512249 (Publication Type: Journal Article)
• Copyright: ©2017 American Association for Cancer Research.

Chemical References

• Multiprotein Complexes
• Sequestosome-1 Protein
• Sqstm1 protein, mouse
• Tsc2 protein, mouse
• Tuberous Sclerosis Complex 2 Protein
• Tumor Suppressor Proteins
• Mechanistic Target of Rapamycin Complex 1
• TOR Serine-Threonine Kinases
• Glutathione

Topics

• Animals
• Carcinogenesis (metabolism, pathology)
• Disease Models, Animal
• Fluorescent Antibody Technique
• Glutathione (biosynthesis)
• Immunohistochemistry
• Kidney Neoplasms (metabolism, pathology)
• Mechanistic Target of Rapamycin Complex 1
• Mice
• Mice, Knockout
• Mitochondria (pathology)
• Multiprotein Complexes (metabolism)
• Sequestosome-1 Protein (metabolism)
• TOR Serine-Threonine Kinases (metabolism)
• Tuberous Sclerosis (metabolism, pathology)
• Tuberous Sclerosis Complex 2 Protein
• Tumor Suppressor Proteins (metabolism)