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Pedersen SF, Flinck M, Pardo LA. The Interplay between Dysregulated Ion Transport and Mitochondrial Architecture as a Dangerous Liaison in Cancer. Int J Mol Sci 2021; 22:ijms22105209. [PMID: 34069047 PMCID: PMC8156689 DOI: 10.3390/ijms22105209] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Revised: 05/08/2021] [Accepted: 05/11/2021] [Indexed: 02/06/2023] Open
Abstract
Transport of ions and nutrients is a core mitochondrial function, without which there would be no mitochondrial metabolism and ATP production. Both ion homeostasis and mitochondrial phenotype undergo pervasive changes during cancer development, and both play key roles in driving the malignancy. However, the link between these events has been largely ignored. This review comprehensively summarizes and critically discusses the role of the reciprocal relationship between ion transport and mitochondria in crucial cellular functions, including metabolism, signaling, and cell fate decisions. We focus on Ca2+, H+, and K+, which play essential and highly interconnected roles in mitochondrial function and are profoundly dysregulated in cancer. We describe the transport and roles of these ions in normal mitochondria, summarize the changes occurring during cancer development, and discuss how they might impact tumorigenesis.
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Affiliation(s)
- Stine F. Pedersen
- Department of Biology, Faculty of Science, University of Copenhagen, 2100 Copenhagen, Denmark;
- Correspondence: (S.F.P.); (L.A.P.)
| | - Mette Flinck
- Department of Biology, Faculty of Science, University of Copenhagen, 2100 Copenhagen, Denmark;
| | - Luis A. Pardo
- Oncophysiology Group, Max Planck Institute for Experimental Medicine, 37075 Göttingen, Germany
- Correspondence: (S.F.P.); (L.A.P.)
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Lin QT, Lee R, Feng AL, Kim MS, Stathopulos PB. The leucine zipper EF-hand containing transmembrane protein-1 EF-hand is a tripartite calcium, temperature, and pH sensor. Protein Sci 2021; 30:855-872. [PMID: 33576522 DOI: 10.1002/pro.4042] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 02/09/2021] [Accepted: 02/09/2021] [Indexed: 12/15/2022]
Abstract
Leucine Zipper EF-hand containing transmembrane protein-1 (LETM1) is an inner mitochondrial membrane protein that mediates mitochondrial calcium (Ca2+ )/proton exchange. The matrix residing carboxyl (C)-terminal domain contains a sequence identifiable EF-hand motif (EF1) that is highly conserved among orthologues. Deletion of EF1 abrogates LETM1 mediated mitochondrial Ca2+ flux, highlighting the requirement of EF1 for LETM1 function. To understand the mechanistic role of this EF-hand in LETM1 function, we characterized the biophysical properties of EF1 in isolation. Our data show that EF1 exhibits α-helical secondary structure that is augmented in the presence of Ca2+ . Unexpectedly, EF1 features a weak (~mM), but specific, apparent Ca2+ -binding affinity, consistent with the canonical Ca2+ coordination geometry, suggested by our solution NMR. The low affinity is, at least in part, due to an Asp at position 12 of the binding loop, where mutation to Glu increases the affinity by ~4-fold. Further, the binding affinity is sensitive to pH changes within the physiological range experienced by mitochondria. Remarkably, EF1 unfolds at high and low temperatures. Despite these unique EF-hand properties, Ca2+ binding increases the exposure of hydrophobic regions, typical of EF-hands; however, this Ca2+ -induced conformational change shifts EF1 from a monomer to higher order oligomers. Finally, we showed that a second, putative EF-hand within LETM1 is unreactive to Ca2+ either in isolation or tandem with EF1. Collectively, our data reveal that EF1 is structurally and biophysically responsive to pH, Ca2+ and temperature, suggesting a role as a multipartite environmental sensor within LETM1.
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Affiliation(s)
- Qi-Tong Lin
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
| | - Rachel Lee
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada.,Temerty Faculty of Medicine, University of Toronto, Toronto, Canada
| | - Allen L Feng
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada.,Faculty of Dentistry, University of Toronto, Toronto, Canada
| | - Michael S Kim
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada.,Department of Radiation Oncology, Dalhousie University, Halifax, Canada
| | - Peter B Stathopulos
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry, University of Western Ontario, London, Ontario, Canada
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