Tamas Balla

Eunice Kennedy Shriver National Institute of Child Health and Human Development, Роквилл, Maryland, United States

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Publications (179)1121.51 Total impact

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    ABSTRACT: Sustained agonist-induced production of the second messengers InsP3 and diacylglycerol requires steady delivery of phosphatidylinositol (PtdIns) from its site of synthesis in the ER to the plasma membrane (PM) to maintain PtdIns(4,5)P2 levels. Similarly, phosphatidic acid (PtdOH), generated from diacylglycerol in the PM, has to reach the ER for PtdIns resynthesis. Here, we show that the Drosophila RdgB homolog, Nir2, a presumed PtdIns transfer protein, not only transfers PtdIns from the ER to the PM but also transfers PtdOH to the opposite direction at ER-PM contact sites. PtdOH delivery to the ER is impaired in Nir2-depleted cells, leading to limited PtdIns synthesis and ultimately to loss of signaling from phospholipase C-coupled receptors. These studies reveal a unique feature of Nir2, namely its ability to serve as a highly localized lipid exchanger that ensures that PtdIns synthesis is matched with PtdIns(4,5)P2 utilization so that cells maintain their signaling competence. Copyright © 2015 Elsevier Inc. All rights reserved.
    Developmental Cell 05/2015; 33(5). DOI:10.1016/j.devcel.2015.04.028 · 10.37 Impact Factor
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    PLoS ONE 05/2015; 10(5):e0125601. DOI:10.1371/journal.pone.0125601 · 3.23 Impact Factor
  • Gerald R.V. Hammond · Tamas Balla
    Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids 05/2015; DOI:10.1016/j.bbalip.2015.05.005 · 4.50 Impact Factor
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    ABSTRACT: Polymicrogyria is a structural brain abnormality involving the cerebral cortex that results from impaired neuronal migration and although several genes have been implicated, many cases remain unsolved. In this study, exome sequencing in a family where 3 fetuses had all been diagnosed with polymicrogyria and cerebellar hypoplasia allowed us to identify regions of the genome for which both chromosomes were shared identical-by-descent, reducing the search space for causative variants to 8.6% of the genome. In these regions, the only plausibly pathogenic mutations were compound heterozygous variants in PI4KA, which Sanger sequencing confirmed segregated consistent with autosomal recessive inheritance. The paternally-transmitted variant predicted a premature stop mutation (c.2386C>T; p.R796X) whilst the maternally-transmitted variant predicted a missense substitution (c.5560G>A; p.D1854N) at a conserved residue within the catalytic domain. Functional studies using expressed wild-type or mutant PI4KA enzyme confirmed the importance of p.D1854 for kinase activity. Our results emphasize the importance of phosphoinositide signalling in early brain development. © The Author 2015. Published by Oxford University Press.
    Human Molecular Genetics 04/2015; 24(13). DOI:10.1093/hmg/ddv117 · 6.68 Impact Factor
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    ABSTRACT: Professional phagocytic cells ingest microbial intruders by engulfing them into phagosomes, which subsequently mature into microbicidal phagolysosomes. Phagosome maturation requires sequential fusion of the phagosome with early endosomes, late endosomes, and lysosomes. Although various phosphoinositides (PIPs) have been detected on phagosomes, it remained unclear which PIPs actually govern phagosome maturation. Here, we analyzed the involvement of PIPs in fusion of phagosomes with various endocytic compartments and identified phosphatidylinositol 4-phosphate [PI(4)P], phosphatidylinositol 3-phosphate [PI(3)P], and the lipid kinases that generate these PIPs, as mediators of phagosome-lysosome fusion. Phagosome-early endosome fusion required PI(3)P, yet did not depend on PI(4)P. Thus, PI(3)P regulates phagosome maturation at early and late stages, whereas PI(4)P is selectively required late in the pathway.
    Proceedings of the National Academy of Sciences 03/2015; 112(15). DOI:10.1073/pnas.1423456112 · 9.81 Impact Factor
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    ABSTRACT: Biased agonism on the type I angiotensin receptor (AT1-R) can achieve different outcomes, via activation of G protein-dependent and -independent cellular responses. In this study, we investigated whether the biased activation of the AT1-R can lead to different regulation and intracellular processing of the receptor. We analyzed β-arrestin binding, endocytosis and subsequent trafficking steps such as early and late phases of recycling of the AT1-R in HEK293 cells expressing wild type or biased mutant receptors in response to different ligands. We used Renilla luciferase tagged receptors and yellow fluorescent protein (YFP) tagged β-arrestin2, Rab5, Rab7 and Rab11 proteins in bioluminescence resonance energy transfer (BRET) measurements to follow the fate of the receptor after stimulation. We found that not only is the signaling of the receptor different upon using selective ligands, but the fate within the cells is also determined by the type of the stimulation. β-arrestin binding and the internalization kinetics of the angiotensin II (AngII)-stimulated AT1-R differed from those stimulated by the biased agonists. Similarly, AngII-stimulated wild type AT1-R showed differences compared to a biased mutant AT1-R (DRY/AAY AT1-R) regarding β-arrestin binding and endocytosis. We suggest that the differences in the internalization kinetics of the receptor in response to biased agonist stimulation are due to the differences in plasma membrane PtdIns(4,5)P2 depletion. Moreover, the stability of the β-arrestin binding is a major determinant of the later fate of the internalized AT1-R receptor. The American Society for Pharmacology and Experimental Therapeutics.
    Molecular pharmacology 03/2015; 87(6). DOI:10.1124/mol.114.097030 · 4.12 Impact Factor
  • Gerald R V Hammond · Tamas Balla
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    ABSTRACT: Polyphosphoinositides (PPIn) are an important family of phospholipids located on the cytoplasmic leaflet of eukaryotic cell membranes. Collectively, they are critical for the regulation of many aspects of membrane homeostasis and signaling, with notable relevance to human physiology and disease. This regulation is achieved through the selective interaction of these lipids with hundreds of cellular proteins, and thus the capability to study these localized interactions is crucial to understanding their functions. In this review, we discuss current knowledge of the principle types of PPIn-protein interactions, focusing on specific lipid-binding domains. We then discuss how these domains have been re-tasked by biologists as molecular probes for these lipids in living cells. Finally, we describe how the knowledge gained with these probes, when combined with other techniques, has led to the current view of the lipids' localization and function in eukaryotes, focusing mainly on animal cells. This article is part of a Special Issue entitled Phosphoinositides. Copyright © 2015. Published by Elsevier B.V.
    Biochimica et Biophysica Acta (BBA) - Molecular and Cell Biology of Lipids 02/2015; 1851(6). DOI:10.1016/j.bbalip.2015.02.013 · 4.50 Impact Factor
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    ABSTRACT: The yeast Efr3p protein is a major regulator of the Stt4p phosphatidylinositol 4-kinase at ER-PM contact sites. Its mutant fly homologue, Rbo displays diminishing light responses attributed to progressively impaired PLC signaling. Here we find that Efr3s play a role in maintaining responsiveness to angiotensin II (AngII) receptors. RNAi-mediated depletion of EFR3A and EFR3B impaired the sustained phase of cytosolic Ca(2+) response to high concentration of AngII in HEK293 cells expressing the wild type but not a truncated AT1a receptor, missing the phosphorylation sites. Efr3 depletion had minimal effect on the recovery of plasma membrane phosphoinositides during stimulation, and AT1 receptors still underwent ligand-induced internalization. A higher level of basal receptor phosphorylation and a larger response was observed after stimulation. Moreover, Gq activation more rapidly desensitized after AngII stimulation in Efr3 downregulated cells. Similar but smaller effect of EFR3 depletion was observed on the desensitization of the cAMP response after isoproterenol stimulation. These data suggest that mammalian Efr3s contribute to the control of the phosphorylation state and hence desensitization of AT1a receptors and could affect GPCR responsiveness in higher eukaryotes.
    Journal of Cell Science 11/2014; 128(1). DOI:10.1242/jcs.157495 · 5.33 Impact Factor
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    ABSTRACT: CDP-diacylglycerol Synthases (CDS)1 are critical enzymes that catalyze the formation of CDP-diacylglycerol (CDP-DAG) from phosphatidic acid (PA). Here we show in vitro that the two isoforms of human CDS, CDS1 and CDS2, show different acyl chain specificities for its lipid substrate. CDS2 is selective for the acyl chains at the sn-1 and sn-2 positions, the most preferred species being 1-stearoyl-2-arachidonoyl-sn-phosphatidic acid. CDS1, conversely, shows no particular substrate specificity, displaying similar activities for almost all substrates tested. Additionally, we show that inhibition of CDS2 by phosphatidylinositol is also acyl chain dependent, with the greatest inhibition seen with the 1-stearoyl-2-arachidonoyl species. CDS1 shows no acyl chain dependent inhibition. Both CDS1 and CDS2 are inhibited by their anionic phospholipid end products, with phosphatidylinositol-(4,5)-bisphosphate showing the greatest inhibition. Our results indicate that CDS1 and CDS2 could create different CDP-DAG pools that may serve to enrich different phospholipid species with specific acyl chains.
    Biochemistry 11/2014; 53(47). DOI:10.1021/bi501250m · 3.01 Impact Factor
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    ABSTRACT: Phosphoinositides are a class of phospholipids generated by the action of phosphoinositide kinases with key regulatory functions in eukaryotic cells. Here, we present the atomic structure of phosphatidylinositol 4-kinase type IIα (PI4K IIα), in complex with ATP solved by X-ray crystallography at 2.8 Å resolution. The structure revealed a non-typical kinase fold that could be divided into N- and C-lobes with the ATP binding groove located in between. Surprisingly, a second ATP was found in a lateral hydrophobic pocket of the C-lobe. Molecular simulations and mutagenesis analysis revealed the membrane binding mode and the putative function of the hydrophobic pocket. Taken together, our results suggest a mechanism of PI4K IIα recruitment, regulation, and function at the membrane.
    EMBO Reports 10/2014; 15(10):1085-1092. DOI:10.15252/embr.201438841 · 7.86 Impact Factor
  • Gerald R V Hammond · Tamas Balla
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    ABSTRACT: The inositol lipids play many essential roles in eukaryotic physiology, although the action has usually focused on the special properties of their headgroup. Now, a study by Clark et al (2014) re-focuses attention on the hydrophobic lipid tails, showing that these too exhibit unique biochemical properties—and are also likely to play a fundamental role in the biology of the lipid.
    The EMBO Journal 09/2014; 33(19). DOI:10.15252/embj.201489773 · 10.75 Impact Factor
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    ABSTRACT: Specificity of membrane fusion in vesicular trafficking is dependent on proper subcellular distribution of soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNAREs). Although SNARE complexes are fairly promiscuous in vitro, significant specificity is achieved in cells due to spatial segregation and shielding of SNARE motifs prior to association with cognate Q-SNAREs. In this study we identified phosphatidylinositol 4-kinase IIα (PI4K2A) as a binding partner of vesicle-associated membrane protein 3 (VAMP3), a small R-SNARE involved in recycling and retrograde transport, and found that the two proteins co-reside on tubulo-vesicular endosomes. PI4K2A knockdown inhibited VAMP3 trafficking to perinuclear membranes and impaired the rate of VAMP3-mediated recycling of the transferrin receptor. Moreover, depletion of PI4K2A significantly decreased association of VAMP3 with its cognate Q-SNARE, Vti1a. Although binding of VAMP3 to PI4K2A did not require kinase activity, acute depletion of PtdIns4P on endosomes significantly delayed VAMP3 trafficking. Phospholipid modulation of SNARE function has been proposed based on in vitro studies and our study provides mechanistic evidence in support of these claims by identifying PI4K2A and PtdIns4P as regulators of an R-SNARE in intact cells.
    Journal of Cell Science 07/2014; 127(17). DOI:10.1242/jcs.148809 · 5.33 Impact Factor
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    ABSTRACT: Polyphosphoinositides are an important class of lipid that recruit specific effector proteins to organelle membranes. One member, phosphatidylinositol 4-phosphate (PtdIns4P) has been localized to Golgi membranes based on the distribution of lipid binding modules from PtdIns4P effector proteins. However, these probes may be biased by additional interactions with other Golgi-specific determinants. In this paper, we derive a new PtdIns4P biosensor using the PtdIns4P binding of SidM (P4M) domain of the secreted effector protein SidM from the bacterial pathogen Legionella pneumophila. PtdIns4P was necessary and sufficient for localization of P4M, which revealed pools of the lipid associated not only with the Golgi but also with the plasma membrane and Rab7-positive late endosomes/lysosomes. PtdIns4P distribution was determined by the localization and activities of both its anabolic and catabolic enzymes. Therefore, P4M reports a wider cellular distribution of PtdIns4P than previous probes and therefore will be valuable for dissecting the biological functions of PtdIns4P in its assorted membrane compartments.
    The Journal of Cell Biology 04/2014; 205(1). DOI:10.1083/jcb.201312072 · 9.69 Impact Factor
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    ABSTRACT: Vascular endothelial growth factor (VEGF) is a critical regulator of endothelial cell differentiation and vasculogenesis during both development and tumor vascularization. VEGF-165 is a major form that is secreted from the cells via a poorly characterized pathway. Here we used GFP and epitope-tagged VEGF-165 and found that its early trafficking between the ER and the Golgi requires the small GTP binding proteins, Sar1 and Arf1- and that its glycosylation in the Golgi compartment is necessary for efficient post Golgi transport and secretion from the cells. The relative temperature insensitivity of VEGF secretion and its Sar1 and Arf1 inhibitory profiles distinguished it from other cargoes using the "constitutive" secretory pathway. Prominent features of VEGF secretion were: the retention of the protein on the outer surface of the plasma membrane and the stimulation of its secretion by Ca(2+) and PKC. Importantly, shedding of VEGF-165 from the cell surface together with other membrane components appears to be a unique feature by which some of VEGF is delivered to the surroundings to exert its known biological actions. Understanding VEGF trafficking can reveal additional means by which tumor vascularization can be inhibited by pharmacological interventions.
    Molecular biology of the cell 02/2014; 25(7). DOI:10.1091/mbc.E13-07-0418 · 5.98 Impact Factor
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    ABSTRACT: Phosphatidylinositol 4-kinase type IIIα (PI4KA) is a host factor essential for hepatitis C virus replication and hence is a target for drug development. PI4KA has also been linked to endoplasmic reticulum exit sites and generation of plasma membrane phosphoinositides. Here, we developed highly specific and potent inhibitors of PI4KA and conditional knock-out mice to study the importance of this enzyme in vitro and in vivo. Our studies showed that PI4KA is essential for the maintenance of plasma membrane phosphatidylinositol 4,5-bisphosphate pools but only during strong stimulation of receptors coupled to phospholipase C activation. Pharmacological blockade of PI4KA in adult animals leads to sudden death closely correlating with the drug's ability to induce phosphatidylinositol 4,5-bisphosphate depletion after agonist stimulation. Genetic inactivation of PI4KA also leads to death; however, the cause in this case is due to severe intestinal necrosis. These studies highlight the risks of targeting PI4KA as an anti-hepatitis C virus strategy and also point to important distinctions between genetic and pharmacological studies when selecting host factors as putative therapeutic targets.
    Journal of Biological Chemistry 01/2014; 289(9). DOI:10.1074/jbc.M113.531426 · 4.57 Impact Factor
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    ABSTRACT: Glycosphingolipid (GSL) trafficking and metabolism are closely linked with cell fate determination, balancing signaling cascades controlling proliferation, apoptosis and autophagy. Altered cellular levels of complex glycosphingolipids often correlate with cancer progression, yet little is known about the principles that guide trafficking of these lipids.
    The FASEB Journal 01/2014; 28(1 Supplement). · 5.48 Impact Factor
  • Tamas Balla
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    ABSTRACT: Phosphoinositides (PIs) make up only a small fraction of cellular phospholipids, yet they control almost all aspects of a cell's life and death. These lipids gained tremendous research interest as plasma membrane signaling molecules when discovered in the 1970s and 1980s. Research in the last 15 years has added a wide range of biological processes regulated by PIs, turning these lipids into one of the most universal signaling entities in eukaryotic cells. PIs control organelle biology by regulating vesicular trafficking, but they also modulate lipid distribution and metabolism via their close relationship with lipid transfer proteins. PIs regulate ion channels, pumps, and transporters and control both endocytic and exocytic processes. The nuclear phosphoinositides have grown from being an epiphenomenon to a research area of its own. As expected from such pleiotropic regulators, derangements of phosphoinositide metabolism are responsible for a number of human diseases ranging from rare genetic disorders to the most common ones such as cancer, obesity, and diabetes. Moreover, it is increasingly evident that a number of infectious agents hijack the PI regulatory systems of host cells for their intracellular movements, replication, and assembly. As a result, PI converting enzymes began to be noticed by pharmaceutical companies as potential therapeutic targets. This review is an attempt to give an overview of this enormous research field focusing on major developments in diverse areas of basic science linked to cellular physiology and disease.
    Physiological Reviews 07/2013; 93(3):1019-137. DOI:10.1152/physrev.00028.2012 · 29.04 Impact Factor
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    ABSTRACT: The BAR (Bin/Amphiphysin/Rvs) domain proteins arfaptin1 and arfaptin2 are localized to the trans-Golgi network (TGN) and, by virtue of their ability to sense and/or generate membrane curvature, could play an important role in the biogenesis of transport carriers. We report that arfaptins contain an amphipathic helix (AH) preceding the BAR domain, which is essential for their binding to phosphatidylinositol 4-phosphate (PI(4)P)-containing liposomes and the TGN of mammalian cells. The binding of arfaptin1, but not arfaptin2, to PI(4)P is regulated by protein kinase D (PKD) mediated phosphorylation at Ser100 within the AH. We also found that only arfaptin1 is required for the PKD-dependent trafficking of chromogranin A by the regulated secretory pathway. Altogether, these findings reveal the importance of PI(4)P and PKD in the recruitment of arfaptins at the TGN and their requirement in the events leading to the biogenesis of secretory storage granules.
    The EMBO Journal 05/2013; 32(12). DOI:10.1038/emboj.2013.116 · 10.75 Impact Factor
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    ABSTRACT: The highly dynamic membranous network of eukaryotic cells allows spatial organization of biochemical reactions to suit the complex metabolic needs of the cell. The unique lipid composition of organelle membranes in the face of dynamic membrane activities assumes that lipid gradients are constantly generated and maintained. Important advances have been made in identifying specialized membrane compartments and lipid transfer mechanisms that are critical for generating and maintaining lipid gradients. Remarkably, one class of minor phospholipids - the phosphoinositides - is emerging as important regulators of these processes. Here, we summarize several lines of research that have led to our current understanding of the connection between phosphoinositides and the transport of structural lipids and offer some thoughts on general principles possibly governing these processes.
    Trends in cell biology 03/2013; 23(6). DOI:10.1016/j.tcb.2013.01.009 · 12.31 Impact Factor
  • The FASEB Journal 01/2013; 27(1_MeetingAbstracts):1017.6. · 5.48 Impact Factor

Publication Stats

11k Citations
1,121.51 Total Impact Points

Institutions

  • 2008–2015
    • Eunice Kennedy Shriver National Institute of Child Health and Human Development
      Роквилл, Maryland, United States
  • 1989–2015
    • National Institutes of Health
      • • Section on Molecular Signal Transduction
      • • Section on Reproductive Endocrinology
      베서스다, Maryland, United States
  • 1987–2012
    • National Institute of Child Health and Human Development
      Maryland, United States
  • 1981–2008
    • Semmelweis University
      • • Department of Physiology
      • • Department of Medical Biochemistry
      Budapeŝto, Budapest, Hungary
  • 2007
    • National Heart, Lung, and Blood Institute
      Maryland, United States
    • Howard Hughes Medical Institute
      Ashburn, Virginia, United States
  • 2005
    • National Eye Institute
      Maryland, United States
  • 2000
    • University of California, San Francisco
      • Department of Cellular and Molecular Pharmacology
      San Francisco, California, United States
  • 1983
    • Semmelweis University
      Budapeŝto, Budapest, Hungary