The mitochondrial nucleoside diphosphate kinase (NDPK-D/NME4), a moonlighting protein for cell homeostasis.

Mitochondrial nucleoside diphosphate kinase (NDPK-D; synonyms: NME4, NM23-H4) represents the major mitochondrial NDP kinase. The homohexameric complex emerged as a protein with multiple functions in bioenergetics and phospholipid signaling. It occurs at different but precise mitochondrial locations and can affect among other mitochondrial shapes and dynamics, as well as the specific elimination of defective mitochondria or cells via mitophagy or apoptosis.

The NDPK/NME superfamily: state of the art.

Nucleoside diphosphate kinases (NDPK) are nucleotide metabolism enzymes encoded by NME genes (also called NM23). Given the fact that not all NME-encoded proteins are catalytically active NDPKs and that NM23 generally refers to clinical studies on metastasis, we use here NME/NDPK to denote the proteins. Since their discovery in the 1950's, NMEs/NDPKs have been shown to be involved in multiple physiological and pathological cellular processes, but the molecular mechanisms have not been fully determined.

NME4/nucleoside diphosphate kinase D in cardiolipin signaling and mitophagy.

Mitophagy is an emerging paradigm for mitochondrial quality control and cell homeostasis. Dysregulation of mitophagy can lead to human pathologies such as neurodegenerative disorders and contributes to the aging process. Complex protein signaling cascades have been described that regulate mitophagy.

Metastasis suppressor NM23 limits oxidative stress in mammals by preventing activation of stress-activated protein kinases/JNKs through its nucleoside diphosphate kinase activity.

(nonmetastatic expressed 1) gene, which encodes nucleoside diphosphate kinase (NDPK) A [also known as nonmetastatic clone 23 (NM23)-H1 in humans and NM23-M1 in mice], is a suppressor of metastasis, but several lines of evidence-mostly from plants-also implicate it in the regulation of the oxidative stress response. Here, our aim was to investigate the physiologic relevance of NDPK A with respect to the oxidative stress response in mammals and to study its molecular basis. -knockout mice died sooner, suffered greater hepatocyte injury, and had lower superoxide dismutase activity than did wild-type (WT) mice in response to paraquat-induced acute oxidative stress.

Mitochondrial NM23-H4/NDPK-D: a bifunctional nanoswitch for bioenergetics and lipid signaling.

A novel paradigm for the function of the mitochondrial nucleoside diphosphate kinase NM23-H4/NDPK-D is proposed: acting as a bifunctional nanoswitch in bioenergetics and cardiolipin (CL) trafficking and signaling. Similar to some other mitochondrial proteins like cytochrome c or AIF, NM23-H4 seems to have dual functions in bioenergetics and apoptotic signaling. In its bioenergetic phosphotransfer mode, the kinase reversibly phosphorylates NDPs into NTPs, driven by mitochondrially generated ATP.

Membrane trafficking. Nucleoside diphosphate kinases fuel dynamin superfamily proteins with GTP for membrane remodeling.

Dynamin superfamily molecular motors use guanosine triphosphate (GTP) as a source of energy for membrane-remodeling events. We found that knockdown of nucleoside diphosphate kinases (NDPKs) NM23-H1/H2, which produce GTP through adenosine triphosphate (ATP)-driven conversion of guanosine diphosphate (GDP), inhibited dynamin-mediated endocytosis. NM23-H1/H2 localized at clathrin-coated pits and interacted with the proline-rich domain of dynamin.

Mitochondrial cardiolipin/phospholipid trafficking: the role of membrane contact site complexes and lipid transfer proteins.

Historically, cellular trafficking of lipids has received much less attention than protein trafficking, mostly because its biological importance was underestimated, involved sorting and translocation mechanisms were not known, and analytical tools were limiting. This has changed during the last decade, and we discuss here some progress made in respect to mitochondria and the trafficking of phospholipids, in particular cardiolipin. Different membrane contact site or junction complexes and putative lipid transfer proteins for intra- and intermembrane lipid translocation have been described, involving mitochondrial inner and outer membrane, and the adjacent membranes of the endoplasmic reticulum.

Dual function of mitochondrial Nm23-H4 protein in phosphotransfer and intermembrane lipid transfer: a cardiolipin-dependent switch.

The nucleoside diphosphate kinase Nm23-H4/NDPK-D forms symmetrical hexameric complexes in the mitochondrial intermembrane space with phosphotransfer activity using mitochondrial ATP to regenerate nucleoside triphosphates. We demonstrate the complex formation between Nm23-H4 and mitochondrial GTPase OPA1 in rat liver, suggesting its involvement in local and direct GTP delivery. Similar to OPA1, Nm23-H4 is further known to strongly bind in vitro to anionic phospholipids, mainly cardiolipin, and in vivo to the inner mitochondrial membrane.

[NM23, an example of a metastasis suppressor gene].

Metastasis suppressor genes - unlike tumor suppressor genes - are defined by their capacity to control metastatic dissemination in vivo without affecting growth of the primary tumor. The first of these metastasis suppressor genes, NM23, was identified in 1988. Since then, expression of NM23 has been studied widely in human tumor cohorts, often with contradictory results.

KIF20A mRNA and its product MKlp2 are increased during hepatocyte proliferation and hepatocarcinogenesis.

Mitotic kinesin-like protein 2 (MKlp2), a microtubule-associated motor, is required during mitosis exit for the final step of cytokinesis. It also contributes to retrograde vesicular trafficking from the Golgi apparatus to the endoplasmic reticulum in interphase. The KIF20A gene encoding MKlp2 is controlled by the E2F-retinoblastoma protein-p16 pathway, and its widely expressed mRNA is found in fetal and proliferating adult tissues.

CXCR7 is up-regulated in human and murine hepatocellular carcinoma and is specifically expressed by endothelial cells.

Development of hepatocellular carcinoma (HCC) is a complex and progressive disease that involves cycles of liver cell death, inflammation, and tissue regeneration/remodelling. Chemokines and chemokine receptors play numerous and integral roles in the disease progression of HCC. Here we investigated the novel chemokine receptor CXCR7/RDC1 in HCC progression, its two known ligands CXCL12 and CXCL11, as well as the other CXCL12 receptor, CXCR4.

Learning about the functions of NME/NM23: lessons from knockout mice to silencing strategies.

The human NME gene family (also known as NM23) comprises ten genes that are involved in diverse physiological and pathological processes including proliferation, differentiation, development, ciliary functions, and metastasis. For the moment, only the NME1, NME2, and NME7 genes have been inactivated in transgenic knockout mice, as well as a double NME1-NME2 gene knockout. Mice lacking NME1 or NME2 grow to adulthood without health problems, although NME1 (-/-) mice have modest growth retardation.

Proteomic analysis of NME1/NDPK A null mouse liver: evidence for a post-translational regulation of annexin IV and EF-1Bα.

NME/NDPK family proteins are involved in the control of intracellular nucleotide homeostasis as well as in both physiological and pathological cellular processes, such as proliferation, differentiation, development, apoptosis, and metastasis dissemination, through mechanisms still largely unknown. One family member, NME1/NDPK-A, is a metastasis suppressor, yet the primary physiological functions of this protein are still missing. The purpose of this study was to identify new NME1/NDPK-A-dependent biological functions and pathways regulated by this gene in the liver.

Aggregation of the neuroblastoma-associated mutant (S120G) of the human nucleoside diphosphate kinase-A/NM23-H1 into amyloid fibrils.

The human nucleoside diphosphate (NDP) kinase A, product of the NME1 gene also named NM23-H1, is known as a metastasis suppressor protein. A naturally occurring variant, S120G, identified in neuroblastomas, possesses native three-dimensional structure and enzymatic activity but displays reduced conformational stability and a folding defect with the accumulation of a "molten globule" folding intermediate during refolding in vitro. As such intermediate has been postulated to be involved in amyloid formation, NDP kinase A may serve as a model protein for studying the relationship between folding intermediates and amyloid fibrils.

Implication of metastasis suppressor NM23-H1 in maintaining adherens junctions and limiting the invasive potential of human cancer cells.

Loss of NM23-H1 expression correlates with the degree of metastasis and with unfavorable clinical prognosis in several types of human carcinoma. However, the mechanistic basis for the metastasis suppressor function of NM23-H1 is obscure. We silenced NM23-H1 expression in human hepatoma and colon carcinoma cells and methodologically investigated effects on cell-cell adhesion, migration, invasion, and signaling linked to cancer progression.

Mitochondrial kinases and their molecular interaction with cardiolipin.

Mitochondrial isoforms of creatine kinase (MtCK) and nucleoside diphosphate kinase (NDPK-D) are not phylogenetically related but share functionally important properties. They both use mitochondrially generated ATP with the ultimate goal of maintaining proper nucleotide pools, are located in the intermembrane/cristae space, have symmetrical oligomeric structures, and show high affinity binding to anionic phospholipids, in particular cardiolipin. The structural basis and functional consequences of the cardiolipin interaction have been studied and are discussed in detail in this review.

The mammalian Nm23/NDPK family: from metastasis control to cilia movement.

Nucleoside diphosphate kinases (NDPK) are encoded by the NME genes, also called NM23. They catalyze the transfer of gamma-phosphate from nucleoside triphosphates to nucleoside diphosphates by a ping-pong mechanism involving the formation of a high energy phospho-histidine intermediate [1, 2]. Besides their known functions in the control of intracellular nucleotide homeostasis, they are involved in multiple physiological and pathological cellular processes such as differentiation, development, metastastic dissemination or cilia functions.

Interaction of NDPK-D with cardiolipin-containing membranes: Structural basis and implications for mitochondrial physiology.

Nucleoside diphosphate kinases (NDPKs/Nm23), responsible for intracellular di- and tri-phosphonucleoside homeostasis, play multi-faceted roles in cellular energetic, signaling, proliferation, differentiation and tumor invasion. The mitochondrial NDPK-D, the NME4 gene product, is a peripheral protein of the inner membrane. Several new aspects of the interaction of NDPK-D with the inner mitochondrial membrane have been recently characterized.

Rescue of the neuroblastoma mutant of the human nucleoside diphosphate kinase A/nm23-H1 by the natural osmolyte trimethylamine-N-oxide.

The point mutation S120G in human nucleoside diphosphate kinase A, identified in patients with neuroblastoma, causes a protein folding defect. The urea-unfolded protein cannot refold in vitro, and accumulates as a molten globule folding intermediate. We show here that the trimethylamine-N-oxide (TMAO) corrects the folding defect and stimulated subunit association.

The nucleoside diphosphate kinase D (NM23-H4) binds the inner mitochondrial membrane with high affinity to cardiolipin and couples nucleotide transfer with respiration.

Nucleoside diphosphate kinase (NDPK/Nm23), responsible for intracellular di- and triphosphonucleoside homeostasis, plays multiple roles in cellular energetics, signaling, proliferation, differentiation and tumor invasion. The only human NDPK with a mitochondrial targeting sequence is NDPK-D, the NME4 gene product, which is a peripheral protein of mitochondrial membranes. Subfractionation of rat liver and HEK 293 cell mitochondria revealed that NDPK-D is essentially bound to the inner membrane.

[NM23 and metastasis suppressor genes: update].

Metastatic dissemination represents a leading cause of death in cancer patients. Elucidating the mechanisms of the metastatic process is therefore essential to control it. Since 1988, when the NME (NM23) gene was discovered, several genes specifically suppressing the metastatic potential of tumor cells, have been identified.

Nm23-H1 homologs suppress tumor cell motility and anchorage independent growth.

Nm23-H1 suppresses metastasis, as well as in vitro cell motility, invasion and anchorage independent growth, in a variety of cancer models. Eight human homologs of Nm23 have been identified that share 26-88% identity with the prototype Nm23-H1. Here, we examine the potential of its homologs, -H2, DR-, -H4 and -H5, to inhibit in vitro correlates of metastasis in two highly metastatic human cell lines, MDA-MB-435 and MDA-MB-231.

Nm23-H1 suppresses tumor cell motility by down-regulating the lysophosphatidic acid receptor EDG2.

Exogenous overexpression of the metastasis suppressor gene Nm23-H1 reduces the metastatic potential of multiple types of cancer cells and suppresses in vitro tumor cell motility and invasion. Mutational analysis of Nm23-H1 revealed that substitution mutants P96S and S120G did not inhibit motility and invasion. To elucidate the molecular mechanism of Nm23-H1 motility suppression, expression microarray analysis of an MDA-MB-435 cancer cell line overexpressing wild-type Nm23-H1 was done and cross-compared with expression profiles from lines expressing the P96S and S120G mutants.