The mitochondrially-localized nucleoside diphosphate kinase D (NME4) is a novel metastasis suppressor

Abstract

Background Mitochondrial nucleoside diphosphate kinase (NDPK-D, NME4, NM23-H4) is a multifunctional enzyme mainly localized in the intermembrane space, bound to the inner membrane. Results We constructed loss-of-function mutants of NDPK-D, lacking either NDP kinase activity or membrane interaction and expressed mutants or wild-type protein in cancer cells. In a complementary approach, we performed depletion of NDPK-D by RNA interference. Both loss-of-function mutations and NDPK-D depletion promoted epithelial-mesenchymal transition and increased migratory and invasive potential. Immunocompromised mice developed more metastases when injected with cells expressing mutant NDPK-D as compared to wild-type. This metastatic reprogramming is a consequence of mitochondrial alterations, including fragmentation and loss of mitochondria, a metabolic switch from respiration to glycolysis, increased ROS generation, and further metabolic changes in mitochondria, all of which can trigger pro-metastatic protein expression and signaling cascades. In human cancer, NME4 expression is negatively associated with markers of epithelial-mesenchymal transition and tumor aggressiveness and a good prognosis factor for beneficial clinical outcome. Conclusions These data demonstrate NME4 as a novel metastasis suppressor gene, the first localizing to mitochondria, pointing to a role of mitochondria in metastatic dissemination.

NME6 is a phosphotransfer-inactive, monomeric NME/NDPK family member and functions in complexes at the interface of mitochondrial inner membrane and matrix

“…TMRM-labelled cells were further incubated for 15 min with 250 µM CCCP (carbonylcyanide m-chlorophenyl hydrazone, Sigma-Aldrich, France), and the mitochondrial membrane potential calculated as a difference of TMRM fluorescence before and after CCCP addition, normalized to mitochondrial mass. Confocal images of Mitotracker GreenFM-stained cells were used for quantification of mitochondrial shape and network parameters as described [ 43 ].…”

“…The aim of this study was to identify basic structural and functional features of the barely studied human NME6, using MDA-MB-231T cells, already extensively used as a model system in NME studies [ 40 – 43 ]. We identify two different NME6 isoforms that are expressed in human cells.…”

ZIP11 Regulates Nuclear Zinc Homeostasis in HeLa Cells and Is Required for Proliferation and Establishment of the Carcinogenic Phenotype

“…Cells were starved for 24 h in DMEM without FBS and cell proliferation was inhibited by treating the cells with Cytosine β-D-Arabinofuranoside (AraC) for 2 h. The monolayers were then scratch-wounded using a sterile 200 μl pipette tip and suspended cells were washed away with PBS twice. The progress of cell migration into the wound was monitored every 24 h until wound closure using the ×10 objective of an Echo Rebel Microscope as previously described ( Lacombe et al, 2021 ). The bottom of the plate was marked for reference, and the same field of the monolayers was photographed immediately after performing the wound (time = 0 h) and at different time points after performing the scratch, as indicated in the figures.…”

The Complex Functions of the NME Family—A Matter of Location and Molecular Activity

“…By genetically manipulating NME1 and NME2 in different cancer cells, Huna et al (University of Lyon, and Sorbonne, Paris, France [ 32 ]) provide now evidence that only NME1, but not NME2 can inhibit early stages of metastasis. Most recently, NME4 was also identified as the first mitochondrial metastasis suppressor [ 33 ]. However, the mechanistic basis of the anti-metastatic role of NMEs is not yet fully understood and likely comprises multiple molecular activities [ 34 ].…”

“…In an alternative anti-metastatic signaling pathway, NME1 interacts with p110α, a catalytic subunit of phosphoinositide 3-kinase (PI3K), to inhibit downstream PI3K-Akt signaling by so far unclear mechanisms [ 37 ]. In case of metastasis suppression by NME4, a primary mechanism is likely the maintenance of a fused mitochondrial network via NME4-controlled, Opa1-dependent mitochondrial fusion [ 33 ], analogous to the NME1/2-controlled dynamin-dependent endocytosis. Loss of NME4 induces fragmentation of the mitochondrial network, which together with altered mitochondria-nuclear retrograde signaling and gene expression favors metastasis.…”