Sphingosine Kinase 1 Is an Intracellular Effector of Phosphatidic Acid

Delon, Christine; Manifava, Maria; Wood, Eleanor; Thompson, Dawn; Krugmann, Sonja; Pyne, Susan; Ktistakis, Nicholas T.

doi:10.1074/jbc.m405771200

Cited by 197 publications

(154 citation statements)

References 53 publications

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“…Structural function analysis of sphingosine kinase have revealed that its C-terminal domain is also important for membrane targeting, suggesting a common feature of proteins containing a conserved DGK catalytic domain (37). These studies by Delon et al (37) identified the binding lipid at the C-terminal region of sphingosine kinase as PA. At this point we cannot conclude that PA binding to the C-terminal domain is responsible for membrane localization.…”

Section: Discussionmentioning

confidence: 99%

Role of the Diacylglycerol Kinase α-Conserved Domains in Membrane Targeting in Intact T Cells

Merino¹,

Sanjuán²,

Moraga

et al. 2007

Journal of Biological Chemistry

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Diacylglycerol kinase (DGK) phosphorylates diacylglycerol to phosphatidic acid, modifying the cellular levels of these two lipid mediators. Ten DGK isoforms, grouped into five subtypes, are found in higher organisms. All contain a conserved C-terminal domain and at least two cysteine-rich motifs of unknown function. DGK␣ is a type I enzyme that acts as a negative modulator of diacylglycerol-based signals during T cell activation. Here we studied the functional role of the DGK␣ domains using mutational analysis to investigate membrane binding in intact cells. We show that the two atypical C1 domains are essential for plasma membrane targeting of the protein in intact cells but unnecessary for catalytic activity. We also identify the C-terminal sequence of the protein as essential for membrane binding in a phosphatidic acid-dependent manner. Finally we demonstrate that, in the absence of the calcium binding domain, receptor-dependent translocation of the truncated protein is regulated by phosphorylation of Tyr 335. This functional study provides new insight into the role of the so-called conserved domains of this lipid kinase family and demonstrates the existence of additional domains that confer specific plasma membrane localization to this particular isoform.The transient generation of lipids at the cell membrane by the concerted action of lipases, kinases, and phosphatases is a very effective mechanism for the localization and activation of signaling molecules. The majority of lipid-modifying enzymes are cytosolic proteins that must in turn translocate to the membrane to modify their substrates. Characterization of the mechanism that governs membrane translocation of these proteins is, thus, essential to assess precisely their role in the regulation of cell responses.The diacylglycerol kinases (DGK) 5 are a family of enzymes that phosphorylate diacylglycerol (DAG) to produce phosphatidic acid (PA); this modulates the levels of these two lipids, both of which have recognized second messenger functions. Early experiments showed that DGK activity occupies a central position in phospholipid synthesis; this enzyme attracted additional interest when it was shown to participate in intracellular signaling (1). DGK activity is found in organisms from bacteria to mammals, although the protein identified as a DGK in bacteria is an integral membrane protein (2) and has little structural homology with the DGK characterized in multicellular organisms (3). Ten DGK isoforms have been identified in mammals and grouped into five subtypes based on the presence of various domains in their primary sequences, which define distinct regulatory motifs.Translocation from one subcellular compartment to another appears to be a general theme in the regulation of DGK proteins. Many of the early data regarding DGK activity regulation refer to changes in DGK activity or localization based on enzymatic studies without specifying the isoform concerned (4, 5). Characterization of the DGK isoforms has broadened the concept that these proteins reg...

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Section: Discussionmentioning

confidence: 99%

Role of the Diacylglycerol Kinase α-Conserved Domains in Membrane Targeting in Intact T Cells

Merino¹,

Sanjuán²,

Moraga

et al. 2007

Journal of Biological Chemistry

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“…Previous studies have suggested that PA may also play a role in membrane localization of SK1 through the direct binding of SK1 with membrane-associated PA formed following phospholipase D activation by protein kinase C (46). More recent studies, however, have suggested that hSK1 associates more strongly in vitro with PS than PA, and therefore, this phospholipid may be more a likely candidate to mediate the membrane association of hSK1 (47).…”

Section: Discussionmentioning

confidence: 99%

The Calmodulin-binding Site of Sphingosine Kinase and Its Role in Agonist-dependent Translocation of Sphingosine Kinase 1 to the Plasma Membrane

Sutherland

Moretti

Hewitt

et al. 2006

Journal of Biological Chemistry

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Sphingosine kinases catalyze the formation of sphingosine 1-phosphate, a bioactive lipid involved in many aspects of cellular regulation, including the fundamental biological processes of cell growth and survival. A diverse range of cell agonists induce activation of human sphingosine kinase 1 (hSK1) and, commonly, its translocation to the plasma membrane. Although the activation of hSK1 in response to at least some agonists occurs directly via its phosphorylation at Ser 225 by ERK1/2, many aspects governing the regulation of this phosphorylation and subsequent translocation remain unknown. Here, in an attempt to understand some of these processes, we have examined the known interaction of hSK1 with calmodulin (CaM). By using a combination of limited proteolysis, peptide interaction analysis, and site-directed mutagenesis, we have identified that the CaM-binding site of hSK1 resides in the region spanned by residues 191-206. Specifically, Phe 197 and Leu 198 are critically involved in the interaction because a version of hSK1 incorporating mutations of both Phe 197 3 Ala and Leu 198 3 Gln failed to bind CaM. We have also shown for the first time that human sphingosine kinase 2 (hSK2) binds CaM, and does so via a CaM binding region that is conserved with hSK1 because comparable mutations in hSK2 also ablate CaM binding to this protein. By using the CaM-binding-deficient version of hSK1, we have begun to elucidate the role of CaM in hSK1 regulation by demonstrating that disruption of the CaM-binding site ablates agonist-induced translocation of hSK1 from the cytoplasm to the plasma membrane, while having no effect on hSK1 phosphorylation and catalytic activation.Sphingosine kinases are important signaling enzymes because of their role in the synthesis of the bioactive lipid sphingosine 1-phosphate (S1P).3 Many studies have shown that S1P can affect a diverse array of biological processes, including calcium mobilization, mitogenesis, apoptosis, atherosclerosis, inflammatory responses, cell motility, and angiogenesis (1-4). Although some of these varied effects of S1P result from its action as a ligand for S1P-specific cell-surface G-protein-coupled receptors (5), significant evidence now exists that indicates S1P can also function intracellularly as a second messenger, particularly in the regulation of cell proliferation and apoptosis (6).Two sphingosine kinases exist in humans (hSK1 and hSK2), with most studies to date focusing on hSK1. Although these two enzymes originate from different genes and differ in size, tissue distribution, developmental expression, substrate specificity, specific activity, and possibly in their cellular roles (7-10), their polypeptide sequences possess a high degree of similarity. In fact, almost all of the hSK1 sequence aligns with regions of the larger hSK2 sequence with 80% overall similarity (45% identity) (7). However, hSK2 also possesses two additional polypeptide regions at its N terminus and within the central region of its sequence that are quite distinct from hSK1.Although hSK...

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“…The adaptor Gab2 is required for the activation of PI3K in mast cells and the production of phosphatidylinositols (including PIP 3 ) are needed for the activation and function of PLD, which in turn produces phosphatidic acid (PA). Both of these lipid messengers can either bind, activate or induce the translocation of SphKs (Delon et al, 2004;Melendez and Khaw, 2002;Olivera, Rosenthal and Spiegel, 1996). In contrast to SphK1, the activation of SphK2 requires Fyn, but seems to be less dependent on the activity of Gab2/PI3K .…”

Section: A Linking Fcεri To Sphingosine Kinase Activationmentioning

confidence: 99%

Chapter 3 New Insights on Mast Cell Activation via the High Affinity Receptor for IgE

Rivera

Fierro

Olivera

et al. 2008

Advances in Immunology

180

154

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Mast cells are innate immune cells that function as regulatory or effector cells and serve to amplify adaptive immunity. These cells also function in adaptive immunity primarily through cell surface Fc receptors that bind immunoglobulin antibodies. The dysregulation of their adaptive role makes them central players in allergy and asthma. Upon encountering an allergen (antigen), which is recognized by immunoglobulin E (IgE) antibodies bound to the high affinity IgE receptor (FcεRI) expressed on their cell surface, mast cells secrete both preformed and newly synthesized mediators of the allergic response. Blocking of these responses is an objective in therapeutic intervention of allergic diseases. Thus, understanding the mechanisms by which antigens elicit mast cell activation (via FcεRI) holds promise towards identifying therapeutic targets. Here we review the most recent advances in understanding antigen-dependent mast cell activation. Specifically, we focus on the requirements for FcεRI activation; the regulation of calcium responses; co-stimulatory signals in FcεRI-mediated mast cell activation and function; and how genetics influences mast cell signaling and responses. These recent discoveries open new avenues of investigation with therapeutic potential.

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Sphingosine Kinase 1 Is an Intracellular Effector of Phosphatidic Acid

Cited by 197 publications

References 53 publications

Role of the Diacylglycerol Kinase α-Conserved Domains in Membrane Targeting in Intact T Cells

Role of the Diacylglycerol Kinase α-Conserved Domains in Membrane Targeting in Intact T Cells

The Calmodulin-binding Site of Sphingosine Kinase and Its Role in Agonist-dependent Translocation of Sphingosine Kinase 1 to the Plasma Membrane

Chapter 3 New Insights on Mast Cell Activation via the High Affinity Receptor for IgE

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