Mammalian Phosphatidylinositol 4‐Kinases

Heilmeyer, Ludwig; Szivák, Ilona; Kakuk, Annamária; Vereb, György

doi:10.1002/tbmb.718540873

Cited by 33 publications

(29 citation statements)

References 25 publications

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“…Consistent with a role for eEF1A2 in phospholipid signaling, we have previously reported that eEF1A2 binds to the lipid kinase phosphatidylinositol-4 kinase III beta (PI4KIII␤) and increases its kinase activity (21). PI4KIII␤ is a member of the PI4K family of lipid kinases that phosphorylates the D4 carbon of the inositol ring in phosphatidylinositol to yield phosphatidylinositol-4 phosphate (PI4P) (5,17). PI4Ks are emerging as important mediators of cell physiology because PI4P is itself a regulatory phospholipid and additionally an obligate precursor for PI(4,5)P 2 and PI(3,4,5)P 3 (4,29).…”

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confidence: 74%

Eukaryotic Elongation Factor 1A2 Cooperates with Phosphatidylinositol-4 Kinase III β To Stimulate Production of Filopodia through Increased Phosphatidylinositol-4,5 Bisphosphate Generation

Jeganathan

Morrow

Amiri

et al. 2008

Molecular and Cellular Biology

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Eukaryotic elongation factor 1 alpha 2 (eEF1A2) is a transforming gene product that is highly expressed in human tumors of the ovary, lung, and breast. eEF1A2 also stimulates actin remodeling, and the expression of this factor is sufficient to induce the formation of filopodia, long cellular processes composed of bundles of parallel actin filaments. Here, we find that eEF1A2 stimulates formation of filopodia by increasing the cellular abundance of cytosolic and plasma membrane-bound phosphatidylinositol-4,5 bisphosphate [PI(4,5)P 2 ]. We have previously reported that the eEF1A2 protein binds and activates phosphatidylinositol-4 kinase III beta (PI4KIII␤), and we find that production of eEF1A2-dependent PI(4,5)P 2 and generation of filopodia require PI4KIII␤. Furthermore, PI4KIII␤ is itself capable of activating both the production of PI(4,5)P 2 and the creation of filopodia. We propose a model for extrusion of filopodia in which eEF1A2 activates PI4KIII␤, and activated PI4KIII␤ stimulates production of PI(4,5)P 2 and filopodia by increasing PI4P abundance. Our work suggests an important role for both eEF1A2 and PI4KIII␤ in the control of PI(4,5)P 2 signaling and actin remodeling.Filopodia are fingerlike projections from the plasma membrane that are the first cellular structures to reach new spaces during cell migration. Filopodia are composed of bundled actin filaments and actin-associated proteins (9, 13). Transmembrane receptors within filopodia respond to extracellular cues and guide directional movement toward chemoattractants (26). In addition, filopodia contain abundant adhesion molecules that regulate cellular attachment to growth substrates and cell-cell interactions (37). As such, filopodia regulate several key physiological processes, including cell migration, wound healing, and development. For example, filopodia are essential for neurogenesis in mice and for cell-cell adhesion during Drosophila melanogaster embryogenesis (9, 13).We have previously described a role for eukaryotic elongation factor 1 alpha 2 (eEF1A2) in the initiation and maintenance of filopodia (1). In several types of mammalian cells, eEF1A2 expression is sufficient to stimulate formation of filopodia (1). eEF1A2 is one of two members of the eEF1A family of proteins, eEF1A1 and eEF1A2. During the elongation phase of protein synthesis, GTP-bound eEF1A proteins interact with amino-acylated tRNA and recruit them to the ribosome (18). While eEF1A1 and eEF1A2 are believed to have equivalent roles in protein translation, their tissue-specific expression patterns are each markedly different. eEF1A1 is expressed ubiquitously, whereas eEF1A2 is detectably expressed only in normal tissues of mammalian heart, brain, and skeletal muscle (24a, 24b, 28). Homozygous deletion of eEF1A2 occurs in the wasted mouse (7). These mice develop normally but suffer from neuromuscular abnormalities and immunodeficiency and die at approximately 1 month of age (35,36). Importantly, eEF1A2 is likely to be a human oncogene, it is highly expressed, and its gene is...

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confidence: 74%

Eukaryotic Elongation Factor 1A2 Cooperates with Phosphatidylinositol-4 Kinase III β To Stimulate Production of Filopodia through Increased Phosphatidylinositol-4,5 Bisphosphate Generation

Jeganathan

Morrow

Amiri

et al. 2008

Molecular and Cellular Biology

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“…While the yeast orthologue of PI4KIII␣ is located at the plasma membrane (17), mammalian PI4KIII␣ mainly resides at the ER (18) but is also located at Golgi membranes (19) and at nucleoli upon exogenous expression (20). The localization of PI4KIII␣ also differs among cell types, since in neuronal cells and other cell types, like COS-7 or B50 cells, it is prominently found in the nuclei (21).…”

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confidence: 99%

Mapping of Functional Domains of the Lipid Kinase Phosphatidylinositol 4-Kinase Type III Alpha Involved in Enzymatic Activity and Hepatitis C Virus Replication

Harak

Radujkovic

Taveneau

et al. 2014

J Virol

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The lipid kinase phosphatidylinositol 4-kinase III alpha (PI4KIII␣) is an endoplasmic reticulum (ER)-resident enzyme that synthesizes phosphatidylinositol 4-phosphate (PI4P). PI4KIII␣ is an essential host factor for hepatitis C virus (HCV) replication. Interaction with HCV nonstructural protein 5A (NS5A) leads to kinase activation and accumulation of PI4P at intracellular membranes. In this study, we investigated the structural requirements of PI4KIII␣ in HCV replication and enzymatic activity. Therefore, we analyzed PI4KIII␣ mutants for subcellular localization, reconstitution of HCV replication in PI4KIII␣ knockdown cell lines, PI4P induction in HCV-positive cells, and lipid kinase activity in vitro. All mutants still interacted with NS5A and localized in a manner similar to that of the full-length enzyme, suggesting multiple regions of PI4KIII␣ are involved in NS5A interaction and subcellular localization. Interestingly, the N-terminal 1,152 amino acids were dispensable for HCV replication, PI4P induction, and enzymatic function, whereas further N-terminal or C-terminal deletions were deleterious, thereby defining the minimal PI4KIII␣ core enzyme at a size of ca. 108 kDa. Additional deletion of predicted functional motifs within the C-terminal half of PI4KIII␣ also were detrimental for enzymatic activity and for the ability of PI4KIII␣ to rescue HCV replication, with the exception of a proposed nuclear localization signal, suggesting that the entire C-terminal half of PI4KIII␣ is involved in the formation of a minimal enzymatic core. This view was supported by structural modeling of the PI4KIII␣ C terminus, suggesting a catalytic center formed by an N-and C-terminal lobe and an armadillo-fold motif, which is preceded by three distinct alpha-helical domains probably involved in regulation of enzymatic activity. IMPORTANCEThe lipid kinase PI4KIII␣ is of central importance for cellular phosphatidylinositol metabolism and is a key host cell factor of hepatitis C virus replication. However, little is known so far about the structure of this 240-kDa protein and the functional importance of specific subdomains regarding lipid kinase activity and viral replication. This work focuses on the phenotypic analysis of distinct PI4KIII␣ mutants in different biochemical and cell-based assays and develops a structural model of the C-terminal enzymatic core. The results shed light on the structural and functional requirements of enzymatic activity and the determinants required for HCV replication. W orldwide, about 170 million people are chronically infected with hepatitis C virus (HCV). HCV is a positive-strand RNA virus and belongs to the family Flaviviridae. The viral genome encompasses about 9.6 kb and codes mainly for a polyprotein of about 3,000 amino acids (aa) that is flanked by nontranslated regions. The polyprotein is cleaved into 10 mature proteins by cellular and viral proteases: core, envelope glycoprotein 1 (E1) and E2, p7, and the nonstructural (NS) proteins NS2, NS3, NS4A, NS4B, NS5A, and NS5B (reviewed...

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“…The first phosphorylation step is undertaken by phosphatidylinositol-4-kinase (PI4K) leading to the production of phosphatidylinositol-4 phosphate (PIP). Two groups of PI4 kinases, PI4K II and PI4K III, that show different sensitivity to the inhibitors Wortmannin, phenyl arsine oxide, and 5′-p-fluorosulfonylbenzoyladenosine (Barylko et al, 2002;Heilmeyer et al, 2003), are known to date. High levels of PI4K III mRNA can be found in various regions of the brain, among them the hippocampus (Zolyomi et al, 2000).…”

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confidence: 99%

Inositol 1,4,5 trisphosphate receptor and chromogranin B are concentrated in different regions of the hippocampus

Nicolay

Hertle

Boehmerle

et al. 2007

J of Neuroscience Research

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Calcium (Ca 2+ ) release from intracellular stores plays a crucial role in many cellular functions in the brain. These intracellular signals have been shown to be transmitted within and between cells. We report a non-uniform distribution of proteins essential for Ca 2+ signaling in acutely prepared brain slice preparations and organotypic slice cultures, both made from rat hippocampus. The Type I inositol-1,4,5 trisphosphate receptor (InsP 3 R1) is the main InsP 3 R subtype in neurons. Immunohistochemistry experiments showed a prominent expression of InsP 3 R1 in the CA1 region of the hippocampus whereas the CA3 region and dentate gyrus (DG) showed only moderate immunoreactivity. In contrast, chromogranin B (CGB), a protein binding to the InsP 3 R1 on the luminal side of the endoplasmic reticular membrane was enriched in the CA3 region whereas DG and the CA1 region showed only faint CGB signals. The neuronal kinases leading to the formation of inositol-1,4,5 trisphosphate (InsP 3 ), phosphatidylinositol-4-kinase (PI4K), and phosphatidylinositol-4-phosphate-5-kinase (PIPK), showed strong immunoreactivity throughout all hippocampal cell fields with differences in the subcellular distribution. Moreover, a distinct band of strong CGB and PIPK immunoreactivity was observed in the CA3 region that coincides with the mossy fiber tract (stratum lucidum). These data show differential expression of the components of the signaling toolkit leading to InsP 3 -mediated Ca 2+ release in cells of the hippocampus. The regulation of these differences may play an important role in various neuropathologic conditions such as Alzheimer's disease, epilepsy, or schizophrenia. Keywords rat; intracellular signaling; calcium; immunohistochemistry; organotypic slice culture Calcium (Ca 2+ ) as an intracellular second messenger plays a crucial role in a variety of neuronal functions like development, excitability, neurotransmitter release, synaptic plasticity, gene transcription, and neurodegeneration (Berridge, 1998 NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript side through voltage-gated, ligand-gated, and possibly store-operated channels (Berridge, 1998) or from internal stores through Ca 2+ channels in the endoplasmatic reticulum (ER), the Golgi apparatus, and the mitochondria (Rizzuto, 2001). The ER is the main intracellular calcium store and it is found throughout the cell (Spacek and Harris, 1997) forming a complex network (Terasaki et al., 1994;Berridge, 1998).Different Ca 2+ signals exhibit distinct temporal and spatial patterns. An increase of intracellular Ca 2+ can either be restricted to the site of Ca 2+ entry or spread throughout the neuron (Augustine et al., 2003). Because an increase in cytosolic Ca 2+ can cause a plethora of cellular effects, all Ca 2+ signals have to be regulated accurately (Usachev and Thayer, 1999). For this purpose, all neurons use a variety of channels, receptors, enzymes, and associated proteins that form a complex Ca 2+ signaling toolkit (Berridge et al., 2003). Th...

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Mammalian Phosphatidylinositol 4‐Kinases

Cited by 33 publications

References 25 publications

Eukaryotic Elongation Factor 1A2 Cooperates with Phosphatidylinositol-4 Kinase III β To Stimulate Production of Filopodia through Increased Phosphatidylinositol-4,5 Bisphosphate Generation

Eukaryotic Elongation Factor 1A2 Cooperates with Phosphatidylinositol-4 Kinase III β To Stimulate Production of Filopodia through Increased Phosphatidylinositol-4,5 Bisphosphate Generation

Mapping of Functional Domains of the Lipid Kinase Phosphatidylinositol 4-Kinase Type III Alpha Involved in Enzymatic Activity and Hepatitis C Virus Replication

Inositol 1,4,5 trisphosphate receptor and chromogranin B are concentrated in different regions of the hippocampus

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