Ian Henry Lambert, Dr.Scient., Lic.Scient.

 

RESEARCH FIELD

 

Regulation of the cellular content of the organic osmolyte taurine in mammalian cells and its physiological implications

 

 

 

RESARCH PROFILE

 

Taurine, present in high concentrations in various mammalian cells, is essential for regulation of cell volume, cellular oxidative status as well as the cellular Ca2+ homeostasis. We have a longstanding record of pursuing central mechanisms of taurine biology, and our current focus is on (i) short-term/long-term regulation of the expression, subcellular localisation and activity of the active taurine uptake system TauT, (ii) characterization of the intracellular signalling cascades/second messenger systems involved in the activation and modulation of the volume-sensitive taurine release pathway, and (iii) characterization of intracellular processes that are affected by modulation of the cellular taurine concentration.

 

 

BACKGROUND

 

The cell volume is an essential parameter in the cellular regulation of secretion, metabolism, cell growth and programmed cell death (apoptosis). This is due to the fact that intracellular cell signalling cascades, which are normally activated by neural and hormonal stimulation, also respond to a shift in cell volume and subsequently elicit changes in membrane transport, metabolism and expression of a variety of genes. Taurine, a biochemical inert amino ethane sulphonic acid, plays quantitatively an important role as a compatible organic osmolyte in cell volume control in mammalian cells and an increase/decrease in the cellular taurine content is often taken as an indication of a shift in the cell volume. Within the recent years it has become evident that taurine not only interferes with cell physiology, i.e., membrane structure and function, ion channel function, cellular Ca2+-homeostasis, and oxidative status (see Fig. 1) but also has an impact on cell faith, i.e., taurine interferes with programmed cell death (apoptosis) which is essential for normal development.

Taurine is abundant in the retina, heart and skeletal muscle, and the intracellular taurine concentration ranges from e.g. 10 mM in mouse fibroblasts, 20 – 50 mM in leukocytes and 40-50 mM in Ehrlich ascites tumour cells. The intracellular taurine concentration is a balance between (i) active taurine uptake via the Na+, Cl--dependent, pH-sensitive and high affinity taurine transporter TauT, (ii) synthesis from cystein/methionine, and (iii) release via either a transport process that resembles TauT working in reverse or a volume-sensitive taurine leak pathway. The total body taurine pool in humans is controlled by TauT located at the brush border of the renal proximal tubule and in the basolateral membrane of the distal nephron. Taurine occurs naturally in animal cells but not in plants. Meat and fish are thus nutritional sources of taurine, whereas vegetarians have to rely on their own taurine synthesis.

 

 

 

Taurine uptake and release systems in mammalian cells

Lambert IH, Neurochemical Research 29: 27-63, 2004

 

 

Taurine synthesis and physiological roles in mammalian cells

Lambert IH, Neurochemical Research 29: 27-63, 2004

 

 

There are several pathways for taurine synthesis but the pathway illustrated appears as the main pathway. Cysteine sulfonic acid decarboxylase, which converts cysteine sulfinic acid to hypotaurine, is the rate-limiting step in the taurine synthesis from methionine and cysteine. Taurine has a range of physiological roles.  Bile salt formation: Taurine is an efficient conjugator for bile salts, as it remains ionized even at the high acidity that occurs at the upper intestine. Humans have the ability to switch from taurine conjugates to glycine conjugates when taurine availability is reduced. Cats are unable to make sufficient taurine and do not use glycine for conjugation and therefore require dietary taurine. Osmoregulation: See text for details. Membrane structure and function: Taurine binds to neutral phospholipids and the taurine - phospholipid interaction, that involves formation of ion pairs between the head groups, affects the membrane property, i.e., architecture and fluidity. Taurine inhibits N-methylation of phospholipids, i.e., conversion of phosphatidyl ethanolamine to phosphatidyl choline. Ca2+ homeostasis: Ca2+ binds to phosphatidyl inositol / phosphatidyl serine, and taurine increases the binding affinity of Ca2+ to phospholipids but reduces the binding capacity, i.e., Ca2+ storage capacity. Taurine affects Ca2+ uptake as well as release. Anti-oxidation: Taurine and to a greater extent hypotaurine have antioxidant activity. Ion channel function: Taurine affects Cl- current and regulates the activity of anion channels. Modulation of neurotransmission: Taurine interacts with the GABA- and glycine-gated family of Cl- channels.

 

RESEARCH PROJECTS 2007-2008

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Inactivation of the volume-sensitive taurine efflux pathway is controlled by ROS

in NIH3T3 cells – not in Ehrlich Lettre cells

Lambert, I.H. Am. J. Physiol. 293: C390-C400. 2007

 

The research projects for 2007/2008 are focused on the expression/regulation of the active taurine transporter TauT and the role of phospholipids/lipid-derivatives and reactive oxygen species in the activation/modulation of the volume-sensitive taurine leak pathway. The current projects are:

 

(i) Active taurine uptake via the taurine transporter TauT is regulated by protein kinases (short-term) and by substrate availability/extracellular tonicity (long-term). Emphasis is on identification of TauT splice-variants, (b) characterisation of protein kinase subtypes involved in the translocation of TauT to specific, subcellular domains/compartments (calveolae, primary cilia, plasma membrane, nucleus), and (c) characterization of cellular elements involved in the substrate-induced down-regulation of TauT expression.

 

(ii) Activation of the volume-sensitve taurine leak pathway and the over-all ability of e.g. fibroblasts to perform a volume regulatory respons following hypotonic exposure involve the sequential activation of PLA2, mobilisation of arachidonic acid from the nucleus, activation of 5-lipoxygenase and presumably direct/indirect lipid messenger-induced activation of the volume-sensitive transporters. Emphasis will be on (a) characterisation of volume-sensitive, Ca2+-dependent/independent PLA2 subtypes and their subcellular localisation, (b) demonstration of arachidonic acid release from subcellular compartments, and (c) lipid-messenger profiling following osmotic pertubation.

 

(iii) Swelling-induced taurine release is modulated/potentiated by Ca2+ and by reactive oxygen species (ROS), produced downstream to PLA2 activation. Emphasis is on the identification/characterisation of (a) volume-sensitive tyrosine kinases/phosphatases, Ca2+-sensitive serine/threonine kinases, (b) ROS producing systems and their volume set-point, and (c) lipid peroxidation following osmotic pertubation. This project includes estimation of small changes in cell volume by a microfluidic technique in colaboration with Dr F. Sachs (Mechanical and Aerospace Engineering Department SUNY-Buffalo),

COLLABORATORS

Members of the Cell Signalling group, Department of Molecular Biology, The August Krogh building.

Prof. F. Sachs, Center of Single Molecule Biophysics, Buffalo, USA.

 

 

CV

 

Address – private:   Palermovej 15, 2. th, 2300, København S,            

Address – work:     Institut for Molekylar Biologi  (IMB), August Krogh building,

                               Biochemical Department, Universitesparken 13, 2100, København Ø, 3532 1697;

                               E-mail: IHLambert@aki.ku.dk

 Education:

1979       Cand.scient., Faculty of Natural Sciences, University of Copenhagen (KU).

1984       Lic.scient., Faculty of Natural Sciences, KU.

2004       Dr. Scient., Faculty of Natural Sciences, KU.

              

 Positions:

1980       Scientific assistent, Laboratoire de Physiologie Animale, Université de Liège, Belgien.

1981       Kandidatstipendiat, The August Krogh Institute, KU.

1984       Seniorstipendiat, The August Krogh Institute, KU.

1987       Adjunkt, The August Krogh Institute, KU.

1988       Scientific visitor at University of North Carolina, Chapel Hill, North Carolina, USA.

1991       Lektor at The August Krogh Institute, today IMB, KU.

Memberships:          

The Physiological Society, London, England; Nordisk Forening for Fysiologi; ASCB, USA

 

 

 

Previous positions of trust

·         Council Member at AKI & IMB, Vice-chairman at AKI & IMB,

·         Member of the research council at AKI, Chairman of “Arbejdsmiljøudvalget” at IMB / August Krogh building,

·         Member of “Samarbejdsudvalget” at IMB, Council member for BigNet at AKI/MBI.

·         Co-organiser of the 5th International Symposium on Cell Volume Regulation in Health and Disease, Copenhagen 2005.

 

Current position of trust:

 

·         Council member of  Campusstaldbestyrelsen (Sundheds- og Naturvidenskab i Øst-Danmark),

·         Member of “Arbejdsmiljøudvalget” at IMB / August Krogh building.

·         Member of evaluation committees for Ph.D., and academic positions. Referee for internationale journals

 

Participation at meetings within the period 2002-2007:

2002    Taurine in the 21st Century, Kauai, Hawaii.

2003    Cell Volume Signaling and Regulation, Dayton, Ohio.

2004    Society for Experimental Biology, Edinburg.

  ---      Phospholipase A2 – Platelet-activating factor and related lipid mediators, Berlin

  ---      ASCB, Washington.

2005        Danish Food Science, LMC, Denmark.

---       Taurine Today.Tampera, Finland.

---       Cell Volume Control in Health and Disease, Copenhagen, Denmark.

2006        Experimental Biology, San Francisco, USA

2007        Symposium on pork quality and drip loss, Bern, Schweiz.

  ---      FEBS, Wien, Østrig

---      6th International Symposium on Cell Volume Regulation in Health and Disease,

          Salzburg, Østrig

 

Teaching – Bachelor and Master level:

·      Major courses: Biochemistry,

·      Cell Biology

·      Molecular Biomedicine,

·      Experimental course in Cell biology and Physiology.

Produktion:

Master-students:     5 (2007), 4 (2006), 3 (2005), 5 (2004), 7 (2003), 3 (2002), 1 (2001), 2 (2000). Current number: 6

Ph.D students:        Martin B. Friis

  KEY-PUBLICATIONS

·         Lambert, I.H. Hoffmann, E.K., Christensen, P. 1987. Role of prostaglandins and leukotrienes in volume regulation in Ehrlich ascites tumor cells. J. Membrane Biol. 98, 7-256.

 

·         Lambert, I.H. 1989. Leukotriene-D4 induced cell shrinkage in Ehrlich ascites tumor cells. J. Membrane Biol. 108, 165-176.

 

·         Lambert, I.H., Hoffmann, E.K., Jørgensen, F. 1989. Membrane potential, anion and cation conductances in Ehrlich ascites tumor cells. J. Membrane Biol. 111, 113-132.

 

·         Lambert. I.H., Hoffmann, E.K. 1993. Regulation of taurine transport in Ehrlich ascites tumor cells. J. Membrane Biol. 131: 67-79.

 

·         Lambert, I.H., Hoffmann, E.K 1994. Cell swelling activates separate taurine and chloride channels in Ehrlich mouse ascites tumor cells. J. Membrane Biol. 142: 289-298.

 

·         Mollerup, J., Lambert, I.H. 1996. Phosphorylation is involved in the regulation of the taurine influx via the -system in Ehrlich ascites tumor cells. J. Membrane Biol. 150: 73-82.

 

·         Jørgensen, N.K., Lambert, I.H., Hoffmann, E.K. 1996. Role of LTD4 in the regulatory volume decrease response in Ehrlich ascites tumor cells. J. Membrane Biol. 151: 159-173.

 

·         Thoroed, S.M., Lauritzen, L., Lambert, I.H., Hansen, H.H., Hoffmann, E.K. 1997. Cell swelling activates phospholipase A2 in Ehrlich ascites tumour cells. J. Membrane Biol. 160 (1): 47-58.

 

·         Mollerup, J., Lambert, I.H. 1998. Calyculin A modulates the kinetic constants for the Na+-coupled taurine transport in Ehrlich ascites tumour cells. Biochemica et Biophysica Acta. 1371, 2: 335-344.

 

·         Pedersen, S., Hoffmann E.H., Hougaard, C., Lambert, I.H. 2000. Cell shrinkage is essential in lysophosphatidic acid signaling  in Ehrlich ascites tumor cells. J. Membrane Biol. 173:19-29.

 

·         Pedersen, S., Lambert, I.H., Thoroed, S.M., Hoffmann, E.K. 2000. Hypotonic cell swelling induces translocation of cPLA2 but not cPLA2  in Ehrlich ascites tumor cells. Eur. J. Biochem. 267: 5531-5539.

 

·         Lambert, I.H., Falktoft, B. 2000. Lysophosphatidylcholine induces taurine release from HeLa cells. J. Membrane Biol. 176: 175-185.

 

·         Lambert, I.H., Nielsen, J.H., Andersen, H.J., Ørtenblad, N. 2001. Cellular model for induction of drip loss in meat. Journal of Agritural and Food Chemistry. 49: 4876-4883.

 

·         Pedersen, S.F., Beisner, K.H., Hougaard, C., Willumsen, B.M., Lambert, I.H., Hoffmann, E.K., 2002. Rho family GTP binding proteins are involved in the regulatory Volume Decrease process in NIH3T3 mouse fibroblasts. J. Physiology, 541.3: 779-796.

 

·         Poulsen, K.A., Litman, T., Eriksen, J., Mollerup, J., Lambert, I.H. 2002. Downregulation of taurine uptake in multidrug resistant Ehrlich ascites tumor cells. Amino Acids, 4: 333-356.

 

·         Lambert, I.H. 2003b. Reactive Oxygen Species regulate swelling-induced taurine efflux in NIH3T3 mouse fibroblasts. J. Membrane Biol. 192: 19-32.

 

·         Ørtenblad, N., Young, J.F., Oksbjerg N., Nielsen, J.H., Lambert, I.H. 2003. Reactive Oxygen Species are important mediators of Taurine Release from skeletal muscle cells. Am. J. Physiol. Cell Physiol.: C1362-C1373.

 

·         Lambert, I.H., 2004a. Regulation of the Cellular Content of the Organic Osmolyte Taurine in Mammalian Cells. Neurochemical Research 29: 27-63.

 

·         Lambert, I.H. 2004b. Modulation of Volume-sensitive Taurine release from NIH3T3 mouse fibroblasts by reactive oxygen species. In Cell Volume and Signaling, Ed. PK Lauf and N.C. Adragna, Springer, Chap. 34: 369-378.

 

·         Falktoft, B., Lambert, I.H. 2004. Ca2+ -mediated potentiation of the swelling-induced taurine efflux from HeLa cells: On the role of calmodulin and novel protein kinase C isoforms. J. Membrane Biol. 201: 59-75.

 

·         Voss, J.W., Christensen, S.T., Pedersen, S.F., Lambert, I.H. 2004. Regulation of the expression and subcellular localisation of the taurine transporter TauT in mouse NIH3T3 fibroblast. European J. Biochem 271: 4636-4658.

 

·         Friss, M.B., Friborg, C., Schneider, L., Nielsen, M-B., Lambert, I.H.,  Christensen, S.T., Hoffmann, E.K. 2005 Apoptotic signaling pathways activated by cell shrinkage in NIH3T3 fibroblasts. J. Physiol. 567.2: 427-443.

 

·         Lambert, I.H., Pedersen, S.P. 2006a. Multiple PLA2 isoforms regulate taurine release in NIH3T3 mouse fibroblasts. Taurine 6. Advances in Experimental Medicine and Biology, Springer, Vol 583.. Eds Simo S. Oja, S and Pirjo Saransaari.: 99-108.

 

·         Lambert, I.H., Pedersen, S.F., Poulsen K.A. 2006b. Activation of PLA2 isoforms by cell swelling and ischemia/hypoxia. Acta Physiologica Scandinavica, 187: 75-85.

 

·         Pedersen, S.F., Poulsen, K.A., Lambert, I.H. 2006. Roles of phospholipase A2 isoforms in the swelling- and melittin-induced arachidonic acid and taurine release in NIH3T3 fibroblasts. Am. J. Physiol., 291: C1286-C1296.

 

·         Poulsen, K.A., Young, J.F., Theil, P., Kolko, M., Oksbjerg, N., Lambert, I.H. 2007. Role of phospholipase A2 in the induction of drip loss in Pork. J. Agricultural and Food Chemistry, 55: 1970-1976.

 

·         Lambert, I.H. 2007. Activation and inactivation of the volume-sensitive taurine leak pathway in NIH3T3 fibroblasts and Ehrlich Lettre ascites cells. Am. J. Physiol. 293: C390-C400.

 

·         Poulsen, K.,A., Pedersen, S.F., Kolko, M., Lambert, I.H. 2007.  Induction of group VIA calcium-independent phospholipase A2 activity during in vitro ischemia in C2C12 myotubes involves differential regulation of its splice variants. Am. J. Physiol. Cell Physiol. C1605-C1615.

 

 

CURRENT FUNDING

2005/2006/2007: 3-year rammebevilling, given to Docent EK Hoffmann (IMBF), Associate Professor IH Lambert (IMBF), MD S Gammeltoft, Glostrup Amtssygehus, Assistant Professor SF Pedersen (IMBF) and Schou Stipendiat ST Christensen (IMBF). Titel: Sensors and Signalling events coupling cell volume, cell proliferation and cell death.

2006/2007: Kræftens Bekæmpelse, 600.000 kr together with Docent EK Hoffmann (IMBF), Assistant professor Stine F. Pedersen (IMBF) and associate professsor Søren T. Christensen (IMBF). Nye targets I cancer behandling: Cellevolumen som signal I control af proliferation, migration, invasion og celledød. 

2007: Forsøgsdyrenes Værn.

 

MASTERS/BACHELOR PROJECTS 2007 - 2008

·         Karakterisering af NADPH-oxidasen i fibroblaster – opbygning og regulering – herunder lysophospholipid medieret regulering af ROS produktionen.

·         Karakterisering af 5-lipoxygenasen i pattedyrceller – opbygning og regulering.

·         Effekt af taurin-depletering/taurin-suplementering på iskæmi-induceret apoptose i pattedyrceller.

·         Intracellulær translokation af det aktive taurin-transporterende systemer TauT – herunder karakterisering af Caseinkinase 1 rolle for binding af Na/Cl til den aktive transportør TauT.

·         Karakterisering af volumen-følsom PLA2 aktivitet i pattedyrceller.

·         Bestemmelse af lipidperoxidation i fibroblaster – herunder analyse for isoprostaner og deres effekt på taurintransporterende systemer.

·         Karakterisering af intracellulær LPA-medieret signalering i fibroblaster.

 

Journal Club 2007 - 2008

Forbeholdt interne specialestuderende

BLOK 1, 2 og 3: Fredage klokken 10-11, Sporvognen i August Krogh bygningen