Direct binding of cytosolic NDP kinases to membrane lipids is regulated by nucleotides

The dosage-dependent effect exerted by the NM23-H1/H2 homolog NDK-1 on distal tip cell migration in C. elegans

Abnormal regulation of cell migration and altered rearrangement of the cytoskeleton are fundamental properties of metastatic cells. The first identified metastasis suppressor NM23-H1, which displays nucleoside-diphosphate kinase (NDPK) activity is involved in these processes. NM23-H1 inhibits the migratory and invasive potential of some cancer cells. Correspondingly, numerous invasive cancer cell lines (eg, breast, colon, oral, hepatocellular carcinoma, and melanoma) display low endogenous NM23 levels. In this review, we summarize mechanisms, which are linked to the anti-metastatic activity of NM23. In human cancer cell lines NM23-H1 was shown to regulate cytoskeleton dynamics through inactivation of Rho/Rac-type GTPases. The Drosophila melanogaster NM23 homolog abnormal wing disc (AWD) controls tracheal and border cell migration. The molecular function of AWD is well characterized in both processes as a GTP supplier of Shi/Dynamin whereby AWD regulates the level of chemotactic receptors on the surface of migrating cells through receptor internalization, by its endocytic function. Our group studied the role of the sole group I NDPK, NDK-1 in distal tip cell (DTC) migration in Caenorhabditis elegans. In the absence of NDK-1 the migration of DTCs is incomplete. A half dosage of NDPK as present in ndk-1 (+/-) heterozygotes results in extra turns and overshoots of migrating gonad arms. Conversely, an elevated NDPK level also leads to incomplete gonadal migration owing to a premature stop of DTCs in the third phase of migration, where NDK-1 acts. We propose that NDK-1 exerts a dosage-dependent effect on the migration of DTCs. Our data derived from DTC migration in C. elegans is consistent with data on AWD's function in Drosophila. The combined data suggest that NDPK enzymes control the availability of surface receptors to regulate cell-sensing cues during cell migration. The dosage of NDPKs may be a coupling factor in cell migration by modulating the efficiency of receptor recycling.

Regulation of heterotrimeric G-protein signaling by NDPK/NME proteins and caveolins: an update

Heterotrimeric G proteins are pivotal mediators of cellular signal transduction in eukaryotic cells and abnormal G-protein signaling plays an important role in numerous diseases. During the last two decades it has become evident that the activation status of heterotrimeric G proteins is both highly localized and strongly regulated by a number of factors, including a receptor-independent activation pathway of heterotrimeric G proteins that does not involve the classical GDP/GTP exchange and relies on nucleoside diphosphate kinases (NDPKs). NDPKs are NTP/NDP transphosphorylases encoded by the nme/nm23 genes that are involved in a variety of cellular events such as proliferation, migration, and apoptosis. They therefore contribute, for example, to tumor metastasis, angiogenesis, retinopathy, and heart failure. Interestingly, NDPKs are translocated and/or upregulated in human heart failure. Here we describe recent advances in the current understanding of NDPK functions and how they have an impact on local regulation of G-protein signaling.

Nucleoside Diphosphate Kinase-C Suppresses cAMP Formation in Human Heart Failure

BACKGROUND

Chronic heart failure (HF) is associated with altered signal transduction via β-adrenoceptors and G proteins and with reduced cAMP formation. Nucleoside diphosphate kinases (NDPKs) are enriched at the plasma membrane of patients with end-stage HF, but the functional consequences of this are largely unknown, particularly for NDPK-C. Here, we investigated the potential role of NDPK-C in cardiac cAMP formation and contractility.

METHODS

Real-time polymerase chain reaction, (far) Western blot, immunoprecipitation, and immunocytochemistry were used to study the expression, interaction with G proteins, and localization of NDPKs. cAMP levels were determined with immunoassays or fluorescent resonance energy transfer, and contractility was determined in cardiomyocytes (cell shortening) and in vivo (fractional shortening).

RESULTS

NDPK-C was essential for the formation of an NDPK-B/G protein complex. Protein and mRNA levels of NDPK-C were upregulated in end-stage human HF, in rats after long-term isoprenaline stimulation through osmotic minipumps, and after incubation of rat neonatal cardiomyocytes with isoprenaline. Isoprenaline also promoted translocation of NDPK-C to the plasma membrane. Overexpression of NDPK-C in cardiomyocytes increased cAMP levels and sensitized cardiomyocytes to isoprenaline-induced augmentation of contractility, whereas NDPK-C knockdown decreased cAMP levels. In vivo, depletion of NDPK-C in zebrafish embryos caused cardiac edema and ventricular dysfunction. NDPK-B knockout mice had unaltered NDPK-C expression but showed contractile dysfunction and exacerbated cardiac remodeling during long-term isoprenaline stimulation. In human end-stage HF, the complex formation between NDPK-C and Gα_i2 was increased whereas the NDPK-C/Gα_s interaction was decreased, producing a switch that may contribute to an NDPK-C-dependent cAMP reduction in HF.

CONCLUSIONS

Our findings identify NDPK-C as an essential requirement for both the interaction between NDPK isoforms and between NDPK isoforms and G proteins. NDPK-C is a novel critical regulator of β-adrenoceptor/cAMP signaling and cardiac contractility. By switching from Gα_s to Gα_i2 activation, NDPK-C may contribute to lower cAMP levels and the related contractile dysfunction in HF.

Two-Step Membrane Binding of NDPK-B Induces Membrane Fluidity Decrease and Changes in Lipid Lateral Organization and Protein Cluster Formation

Nucleoside diphosphate kinases (NDPKs) are crucial elements in a wide array of cellular physiological or pathophysiological processes such as apoptosis, proliferation, or metastasis formation. Among the NDPK isoenzymes, NDPK-B, a cytoplasmic protein, was reported to be associated with several biological membranes such as plasma or endoplasmic reticulum membranes. Using several membrane models (liposomes, lipid monolayers, and supported lipid bilayers) associated with biophysical approaches, we show that lipid membrane binding occurs in a two-step process: first, initiation by a strong electrostatic adsorption process and followed by shallow penetration of the protein within the membrane. The NDPK-B binding leads to a decrease in membrane fluidity and formation of protein patches. The ability of NDPK-B to form microdomains at the membrane level may be related to protein-protein interactions triggered by its association with anionic phospholipids. Such accumulation of NDPK-B would amplify its effects in functional platform formation and protein recruitment at the membrane.

Nucleoside diphosphate kinases (NDPKs) in animal development

In textbooks of biochemistry, nucleoside diphosphate conversion to a triphosphate by nucleoside diphosphate 'kinases' (NDPKs, also named NME or NM23 proteins) merits a few lines of text. Yet this essential metabolic function, mediated by a multimeric phosphotransferase protein, has effects that lie beyond a simple housekeeping role. NDPKs attracted more attention when NM23-H1 was identified as the first metastasis suppressor gene. In this review, we examine these NDPK enzymes from a developmental perspective because of the tractable phenotypes found in simple animal models that point to common themes. The data suggest that NDPK enzymes control the availability of surface receptors to regulate cell-sensing cues during cell migration. NDPKs regulate different forms of membrane enclosure that engulf dying cells during development. We suggest that NDPK enzymes have been essential for the regulated uptake of objects such as bacteria or micronutrients, and this evolutionarily conserved endocytic function contributes to their activity towards the regulation of metastasis.

CFTR: a hub for kinases and crosstalk of cAMP and Ca2+

Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator (CFTR). The resulting disease is pleiotropic consistent with the idea that CFTR acts as a node within a network of signalling proteins. CFTR is not only a regulator of multiple transport proteins and controlled by numerous kinases but also participates in many signalling pathways that are disrupted after expression of its commonest mutant (F508del-CFTR). It operates in membrane compartments creating a scaffold for cytoskeletal elements, surface receptors, kinases and phosphodiesterases. CFTR is exposed to membrane-local second messengers such that a CFTR-interacting, low cellular energy sensor kinase (AMP- and ADP-activated kinase, AMPK) signals through a high energy phosphohistidine protein kinase (nucleoside diphosphate kinase, NDPK). CFTR also translocates a Ca(2+)-dependent adenylate cyclase to its proximity so that a rigid separation between cAMP-dependent and Ca(2+)-dependent regulation of Cl(-) transport becomes obsolete. In the presence of wild-type CFTR, parallel activation of CFTR and outwardly rectifying anoctamin 6 Cl(-) channels is observed, while the Ca(2+)-activated anoctamin 1 Cl(-) channel is inhibited. In contrast, in CF cells, CFTR is missing/mislocalized and the outwardly rectifying chloride channel is attenuated while Ca(2+)-dependent Cl(-) secretion (anoctamin 1) appears upregulated. Additionally, we consider the idea that F508del-CFTR when trapped in the endoplasmic reticulum augments IP3-mediated Ca(2+) release by providing a shunt pathway for Cl(-). CFTR and the IP3 receptor share the characteristic that they both assemble their partner proteins to increase the plasticity of their hub responses. In CF, the CFTR hub fails to form at the plasma membrane, with widespread detrimental consequences for cell signalling.

Nucleoside diphosphate kinase B is required for the formation of heterotrimeric G protein containing caveolae

Caveolae are flask-shaped invaginations in the plasma membrane that serve to compartmentalize and organize signal transduction processes, including signals mediated by G protein-coupled receptors and heterotrimeric G proteins. Herein we report evidence for a close association of the nucleoside diphosphate kinase B (NDPK B) and caveolin proteins which is required for G protein scaffolding and caveolae formation. A concomitant loss of the proteins NDPK B, caveolin isoforms 1 (Cav1) and 3, and heterotrimeric G proteins occurred when one of these proteins was specifically depleted in zebrafish embryos. Co-immunoprecipitation of Cav1 with the G protein Gβ-subunit and NDPK B from zebrafish lysates corroborated the direct association of these proteins. Similarly, in embryonic fibroblasts from the respective knockout (KO) mice, the membrane content of the Cav1, Gβ, and NDPK B was found to be mutually dependent on one another. A redistribution of Cav1 and Gβ from the caveolae containing fractions of lower density to other membrane compartments with higher density could be detected by means of density gradient fractionation of membranes derived from NDPK A/B KO mouse embryonic fibroblasts (MEFs) and after shRNA-mediated NDPK B knockdown in H10 cardiomyocytes. This redistribution could be visualized by confocal microscopy analysis showing a decrease in the plasma membrane bound Cav1 in NDPK A/B KO cells and vice versa and a decrease in the plasma membrane pool of NDPK B in Cav1 KO cells. Consequently, ultrastructural analysis revealed a reduction of surface caveolae in the NDPK A/B KO cells. To prove that the disturbed subcellular localization of Cav1 in NDPK A/B KO MEFs as well as NDPK B in Cav1 KO MEFs is a result of the loss of NDPK B and Cav1, respectively, we performed rescue experiments. The adenoviral re-expression of NDPK B in NDPK A/B KO MEFs rescued the protein content and the plasma membrane localization of Cav1. The expression of an EGFP-Cav1 fusion protein in Cav1-KO cells induced a restoration of NDPK B expression levels and its appearance at the plasma membrane. We conclude from these findings that NDPK B, heterotrimeric G proteins, and caveolins are mutually dependent on each other for stabile localization and caveolae formation at the plasma membrane. The data point to a disturbed transport of caveolin/G protein/NDPK B complexes from intracellular membrane compartments if one of the components is missing.

A Cys/Ser mutation of NDPK-A stabilizes its oligomerization state and enhances its activity

Nucleoside diphosphate phosphate transferase A (NDPK-A) has been shown to play critical roles in the regulation of proliferation, differentiation, growth and apoptosis of cells. Our previous study suggested that the disulphide cross-linkage between cysteine 4 (C4) and cysteine 145 (C145) of NDPK-A might be a possible regulator of its activity. To confirm this hypothesis, the C145 residue of NDPK-A was mutated to serine, and the isomerization and biological activities of the mutant were investigated and compared with those of its wild-type counterpart. It was found the C145S mutation eliminated the intramolecular disulphide bond (DB) and prevented the formation of intermolecular DB, which was known to dissociate the hexameric NDPK-A into dimeric one. We also demonstrated that the C145S mutation didn't affect the autologous hexamerization of this protein, and the mutant had increased bioactivities including phosphate transferase and DNase. These findings support the hypothesis that the formation of DBs in NDPK-A is involved in the regulation of the oligomerization and bioactivity of this multiple function protein, and that C145 is a key residue in the regulation of NDPK-A. In addition, the C145S mutant that we have constructed might be an attractive candidate for use in applications that require NDPK-A.

Evaluation of chloroform/methanol extraction to facilitate the study of membrane proteins of non-model plants

Membrane proteins are of great interest to plant physiologists because of their important function in many physiological processes. However, their study is hampered by their low abundance and poor solubility in aqueous buffers. Proteomics studies of non-model plants are generally restricted to gel-based methods. Unfortunately, all gel-based techniques for membrane proteomics lack resolving power. Therefore, a very stringent enrichment method is needed before protein separation. In this study, protein extraction in a mixture of chloroform and methanol in combination with gel electrophoresis is evaluated as a method to study membrane proteins in non-model plants. Benefits as well as disadvantages of the method are discussed. To demonstrate the pitfalls of working with non-model plants and to give a proof of principle, the method was first applied to whole leaves of the model plant Arabidopsis. Subsequently, a comparison with proteins extracted from leaves of the non-model plant, banana, was made. To estimate the tissue and organelle specificity of the method, it was also applied on banana meristems. Abundant membrane or lipid-associated proteins could be identified in both tissues, with the leaf extract yielding a higher number of membrane proteins.

Nucleoside diphosphate kinase (NDPK, NM23, AWD): recent regulatory advances in endocytosis, metastasis, psoriasis, insulin release, fetal erythroid lineage and heart failure; translational medicine exemplified

The guest editor (AM) provides his perspective on the most recent advances on nucleoside diphosphate kinase (NDPK, otherwise known as AWD or NM23) showcasing phospho-histidine biochemistry and its impact on diverse pathology when disordered. His co-author (SO) provides state-of-the-art analyses from the European institute of Bioinformatics in an appendix to support the most recent advances made by the NDPK community. Unfortunately, to those outside the field, NDPK is often dismissed as a tiny ‘ancient housekeeper’ protein found in marine sponges, social amoebae, worms, fruit flies, rodents and humans but the state-of-the-art papers overviewed here show that NDPK does not act simply in mindless rote, inter-converting cellular ‘energy currencies’. That two NDPK isoforms regulate fetal erythroid lineage is a developmental case in point. Seminal Cancer Research UK support is gratefully acknowledged that generated additional resources to enable the NDPK community to meet in Dundee in 2007 (www.dundee.ac.uk/mchs/ndpk; next meeting is planned: 2010/Mannheim-Heidelberg). The presented papers illustrate the point that when scientists are left alone ‘shut up in the narrow cell of their laboratory’ (as the philosopher Ortega once said, a sentiment echoed by Erwin Schrödinger), then progress will ultimately occur bridging the gap between specialization and translation for human benefit. To aid translation, this overview initially introduces the NDPK family to the non-specialist, who serendipitously finds these proteins in their biology. This is immediately followed by examples of the diverse biology generated by this self-aggregating group of multi-functional proteins and finally capped by an emerging idea explaining how this diversity might arise.

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. Over the past 15 years, ten human genes have been discovered encoding partial, full length, and/or tandemly repeated Nm23/NDPK domains, with or without N-or C-terminal extensions and/or additional domains. These genes encode proteins exhibiting different functions at various tissular and subcellular localizations. Most of these genes appear late in evolution with the emergence of the vertebrate lineage. This review summarizes the present knowledge on these multitalented proteins.

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. Over the past 15 years, ten human genes have been discovered encoding partial, full length, and/or tandemly repeated Nm23/NDPK domains, with or without N-or C-terminal extensions and/or additional domains. These genes encode proteins exhibiting different functions at various tissular and subcellular localizations. Most of these genes appear late in evolution with the emergence of the vertebrate lineage. This review summarizes the present knowledge on these multitalented proteins.

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. Surface plasmon resonance analysis using recombinant NDPK-D and different phospholipid liposomes showed that NDPK-D interacts electrostatically with anionic phospholipids, with highest affinity observed for cardiolipin, a phospholipid located mostly in the mitochondrial inner membrane. Mutation of the central arginine (R90) in a surface exposed cationic RRK motif unique to NDPK-D strongly reduced phospholipid interaction in vitro and in vivo. Stable expression of NDPK-D proteins in HeLa cells naturally almost devoid of this isoform revealed a tight functional coupling of NDPK-D with oxidative phosphorylation that depends on the membrane-bound state of the enzyme. Owing to its symmetrical hexameric structure exposing membrane binding motifs on two opposite sides, NDPK-D could bridge liposomes containing anionic phospholipids and promote lipid transfer between them. In vivo, NDPK-D could induce intermembrane contacts and facilitate lipid movements between mitochondrial membranes. Most of these properties are reminiscent to those of the mitochondrial creatine kinase. We review here the common properties of both kinases and we discuss their potential roles in mitochondrial functions such as energy production, apoptosis and mitochondrial dynamics.