Kahn Lab
Research
My laboratory is focused on two recently discovered vascular roles of the Syk and SLP-76 (immunoreceptor) signaling pathway: lymphatic vascular development and platelet activation by collagen during arterial thrombosis.
I. The role of Syk and SLP-76 signaling during separation of the blood and lymphatic vascular networks. Mice lacking Syk or SLP-76 exhibit lethal vascular phenotypes that we have recently found to be due to a failure to separate emerging lymphatic vessels from pre-existing blood vessels. Surviving SLP-76 mice exhibit cardiomegaly and a high cardiac output state (figure 1) due to vascular shunting of blood through the lymphatic vessels (figure 2). We have shown that mixing of the blood and lymphatic circulations occurs at the onset of lymphatic development in these mice and that the phenotype can be conferred by transplantation of deficient marrow into lethally irradiated wild-type mice but we do not yet know how. A major effort in the laboratory is to identify the cell type(s) and receptor(s) responsible for this molecular distinction using genetic approaches in mice and signaling studies of primary endothelial cells from knockout animals. The long term goals of this project are to identify the molecular pathways involved in the development of distinct blood and lymphatic vascular systems.
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Figure 1. SLP-76-deficient mice exhibit cardiomegaly and elevated cardiac outputs. a, Gross cardiomegaly in a slp-76 -/- heart (-/-) compared to that of a wild-type (+/+) littermate at age 2 months. b, Cardiac hypertrophy in slp-76 -/- mice (-/-) is manifest by an elevated heart/body mass ratio compared to wild-type (+/+) and heterozygous (+/-) mice. c, Cardiac MRI reveals dilated chambers in slp-76 -/- hearts with normal ventricular function. Representative cross-sections through wild-type (+/+) and slp-76 -/- (-/-) hearts at the level of the papillary muscles are shown. Note the larger size of the left (LV) and right (RV) ventricular chambers in the slp-76 -/- heart at peak relaxation (diastole) but normal residual volumes at peak contraction (systole). d, slp-76 -/- mice have markedly elevated resting cardiac outputs. |
II. Collagen activation of platelets during arterial thrombosis. Activation of platelets at sites of arterial injury is the first step in a chain of molecular and cellular events that culminate in heart attack and stroke. The primary activating ligand in this setting is collagen, an abundant matrix protein exposed by endothelial damage or loss. Collagen activation of platelets is initiated by the glycoprotein VI receptor, a homologue of immune receptors expressed exclusively on platelets and coupled to Syk and SLP-76 through an ITAM. A second receptor for collagen on platelets is the integrin a2b1 which also couples to Syk and SLP-76 but through a distinct, ITAM-independent manner. We are presently using mouse genetic models and collagen-responsive cell lines developed in our laboratory to determine how collagen activates platelets using these two structurally distinct receptors coupled to a common intracellular signaling pathway. The long term goals of this project are to understand the first steps in the development of arterial thrombi during myocardial infarction and stroke and to define the mechanism by which two such different receptors couple to this signaling pathway.
| Figure 2. FITC-dextran injection demonstrates communication between the blood and lymphatic circulations in slp-76 -/- mice. Fluorescent imaging of mesenteric vessels following left ventricular injection of FITC-dextran injection in wild-type mice (+/+) identifies sets of two blood vessels (artery and vein, left panels) but not lymphatics (arrows). Imaging of injected slp-76 -/- mice (-/-) identifies three vessels (artery, vein and lymphatic (arrow), right panels). |  |
Movies 1 and 2. Cardiac MRI reveals normal heart function in slp 76 -/- mice. ECG-gated transverse images were obtained at the level of the papillary muscles and collated to create movie of a wild-type (Supplemental Movie S1) and slp 76 -/- (Supplemental Movie S2) heart function during a single cardiac cycle.
Movies 3 and 4. First pass angiography of live wild-type (movie S4) and SLP-76-deficient (movie S5) mice reveals vascular continuity between blood and lymphatic vessels and early venous filling in SLP-76-deficient animals consistent with shunting. Real-time video microscopy of the intestinal vasculature was performed following injection of FITC-dextran into the jugular vein. Note the simultaneous filling of both vein and lymphatic following arterial filling in the SLP-76-deficient animal and the failure of arterial FITC-dextran to wash out prior to venous and lymphatic filling.
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Publications
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Latest Publications:
Heiser, J.M., Kahn, M.L., Schmidt, T.A. Functional airway obstruction presenting as stridor: a case report and literature review. Journal of Emergency Medicine. 1990 8:285-9.
Lee, S.W., Kahn, M.L., Dichek, D.A. Expression of an anchored urokinase in the apical endothelial cell membrane. Journal of Biological Chemistry. 1992 267:13020-27.
Kahn, M.L., Lee, S.W., Dichek, D.A. Optimization of retroviral vector-mediated gene transfer into endothelial cells in vitro. Circulation Research. 1992, 71(6):1508-17.
Lee S.W.; Kahn M.L.; Dichek D.A. Control of clot lysis by gene transfer. Trends in Cardiovascular Medicine, 1993 3(2):61-66.
Kahn, M.L. Eisenmenger syndrome in pregnancy. New England Journal of Medicine, 1993 329(12): 887.
Bohm, S., Kong, W., Bromme, D., Smeekens, S.P., Anderson, D.C., Connolly, A., Kahn, M.L.,Nelken, N.A., Coughlin, S.R., Payan, D.G., and Bunnett, N.W. Molecular cloning, expression and potential function of the human proteinase-activated receptor 2. Biochem. J., 1996 314:1009-1016.
Kahn, M.L., Ishii, K., Wu, R., and Coughlin, S.R. Conserved structure and adjacent location of the thrombin receptor and protease-activated receptor 2 genes define a protease-activated receptor gene cluster. Molecular Medicine, 1996, 2(3): 349-357.
Connolly, A., Ishihara, H., Kahn, M.L., Farese, R.V., Jr., and Coughlin, S.R. Role of the thrombin receptor in development and evidence for a second receptor. Nature , 1996, 381: 516-19.
Ishihara, H., Connolly, A.J., Zeng, D., Kahn, M.L., Zheng, Y.W., Timmons, C., Tram, T., Coughlin, S.R. Protease-activated receptor 3 is a second thrombin receptor in humans. Nature, 1997, 386: 502-506.
Kahn, M.L., Zheng, Y.W., Huang,W., Bigornia, V., Zeng, D., Moff, S., Farese, R., Tam, C. and Coughlin, S.R. A two thrombin receptor system for platelet activation. Nature, 1998, 394: 690-694.
Kahn, M.L., Hammes, S.R., Botka, C. and Coughlin, SR. Gene and locus structure and chromosomal localization of the protease-activated receptor gene family. Journal of Biological Chemistry, 1998, 273: 23290-23296.
Kahn, M.L., Nakanishi-Matsui, M., Shapiro, M.S., Ishihara, H. and Coughlin, S.R. PAR1 and PAR4 mediate activation of human platelets by thrombin. Journal of Clinical Investigation, 1999, 103(6):879-87.
Kahn, M.L., Diacovo, T.G., Bainton, D.F., Lanza, F., and Coughlin, S.R. GlycoproteinV-deficient platelets do not exhibit a Bernard-Soulier phenotype and retain normal thrombin responsiveness. Blood, 1999 94: 4112-21.
Lindner, J.R., Kahn, M.L., Coughlin, S.R., Sambrano, G., Schauble, E., Bernstein, D., Foy, D., Hafezi-Moghadam, A. and Ley, K. Delayed onset of inflammation in protease-activated receptor-2 (PAR-2) deficient mice. Journal of Immunology 2000 165: 6504-6510.
Zheng, Y.M., Liu, C., Hong, C., Locke, D., Ryan, J. and Kahn, M.L. Expression of the platelet receptor GPVI confers signaling via the Fc receptor γ-chain to the snake venom convulxin but not to collagen. Journal of Biological Chemistry 2001 276 (16) 12999-13006.
O'Brien PJ, Molino M, Kahn M, Brass LF. Protease activated receptors: theme and variations. Oncogene 2001 20 (13):1570-81.
Moog S, Mangin P, Lenain N, Strassel C, Ravanat C, Schuhler S, Freund M, Santer M, Kahn M, Nieswandt B, Gachet C, Cazenave JP, Lanza F. Platelet glycoprotein V binds to collagen and participates in platelet adhesion and aggregation. Blood. 2001 98 (4):1038-46.
Tulasne D, Judd BA, Johansen M, Asazuma N, Best D, Brown EJ, Kahn M, Koretzky GA, Watson SP. C-terminal peptide of thrombospondin-1 induces platelet aggregation through the Fc receptor gamma-chain-associated signaling pathway and by agglutination. Blood 2001; 8(12):3346-52.
Chen H, Locke D, Liu Y, Liu C, Kahn M.L. The platelet receptor GPVI mediates both adhesion and signaling responses to collagen in a receptor density-dependent fashion. Journal of Biological Chemistry 2002 277(4):3011-9.
Locke D, Chen H, Liu Y, Liu C, Kahn ML. Lipid rafts orchestrate signaling by the platelet receptor glycoprotein VI. J Biol Chem, 277: 18801 - 18809, 2002
Camerer E, Kataoka H, Kahn M, Lease K, Coughlin SR. Genetic evidence that protease-activated receptors mediate factor Xa signaling in endothelial cells. J Biol Chem 2002 May 3;277(18):16081-7.
Larson MK, Chen H, Kahn ML, Taylor AM, Fabre JE, Mortensen RM, Conley PB, Parise LV. Identification of P2Y12-dependent and independent mechanisms of glycoprotein VI-mediated Rap1 activation in platelets. Blood 2003 101 (4).
Abtahian F, Guerriero A, Sebzda E, Lu M, Mocsai A, Myers E, Huang B, Jackson D, Ferrari A, Tybulewicz V, Lowell A, Lepore J, Koretzky G, Kahn M. Regulation of blood and lymphatic vascular separation by signaling proteins SLP-76 and Syk. Science 2003 299(10): 247-251.
Locke D, Liu C, Peng X, Chen H, Kahn ML. Fc Rγ -independent Signaling by the Platelet Collagen Receptor Glycoprotein VI. J Biol Chem. 2003 Apr 25;278(17):15441-8.
Chen H, Kahn ML. Reciprocal Singnaling by Integrin and Nonintrgrin Receptors during Collagen Activation of Platelets. Molecular and Cellular Biology 2003 23 (14) 4767-4777.
Boylan B., Chen H, Rathore V, Paddock C, Salacz M, Friedman KD, Curtis BR, Stapleton M, Newman DK, Kahn ML, Newman PJ. Anti-GPVI-associated ITP: An acquired platelet disorder caused by autoantibody-mediated clearance of the GPVI/FcRgamma-chain complex from the human platelet surface. Blood (2004), 104: 1350-1355.
Sarratt K, Chen H, Kahn ML, Hammer DA. Platelet receptor, glycoprotein VI-mediated adhesion to type I collagen under hydrodynamic flow. American Society for Biomedical Engineering (2004) in press.
Xu, B., deWaal, R., Mor-Viknin, N., Hibbard, C., Markovitz, D.M., Kahn, M.L. The endothelial-specific antibody PAL-E identifies a secreted form of vimentin in the blood vasculature. Molecular and Cellular Biology, 24 (20):9198-9206, 2004.
Gardiner, E.E., Arthur, J.F., Kahn ML, Berndt, M.C. and Andrews R.K. Regulation of Platelet Membrane Levels of Glycoprotein VI by a Platelet-Derived Metalloproteinase. Blood. 2004 Aug 12.
Sarratt, KL, Chen, H, Zutter, MM, Santoro, SA, Hammer, DA, Kahn, ML. GPVI and α2β1 play independent critical roles during platelet adhesion and aggregate formation to collagen under flow. Blood, submitted and revised March 2005.
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Contact
Mark L. Kahn
BRB II/III Room 952
421 Curie Blvd
University of Pennsylvania
Philadelphia, PA 19104-6160
Email: markkahn@mail.med.upenn.edu
Phone: 215-898-9007
Fax: 215-573-2094
Patricia Mericko - Lab Manager
BRB II/III Room 934
421 Curie Blvd
University of Pennsylvania
Philadelphia, PA 19104-6160
Email: pmericko@mail.med.upenn.edu
Phone: 215-573-7069
Fax: 215-573-2094
Nina Maschak , Administrative Coordinator
Email: maschak@mail.med.upenn.edu
Phone: 215-573-8002
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Lab Members
Patricia Mericko, Lab Manager, 215-573-7069, pmericko@mail.med.upenn.edu
Cara Bertozzi, 215-573-1191, bertozzi@mail.med.upenn.edu
Chiu-Yu Chen, 215-573-1191, chiuyu.chen@gmail.com
Mei Chen, 215-573-7142, chenmei@mail.med.upenn.edu
Ben Kleaveland, 215-573-7142, kleavela@mail.med.upenn.edu
John Lee, 215-573-1191, john.lee@uphs.upenn.edu
Alec Schmaier, 215-573-1191, schmaier@mail.med.upenn.edu
Shawn Sweeney, 215-898-7311, shawnms@mail.med.upenn.edu
Xiangjian Zheng, 215-573-7142, zhengx2@mail.med.upenn.edu
Zhiying Zou, 215-898-7311, zzou@mail.med.upenn.edu
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