This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this book Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Peters, K. G. Articles by Sankar, S. Search for Related Content PubMed PubMed Citation Articles by Peters, K. G. Articles by Sankar, S.

Functional Significance of Tie2 Signaling in the Adult Vasculature

Kevin G. Peters^*, Christopher D. Kontos, P. Charles Lin, Adrianne L. Wong^||, Prema Rao^¶, Liwen Huang^**, Mark W. Dewhirst and Sabita Sankar

^* Procter and Gamble Pharmaceuticals, Health Care Research Center, Mason, Ohio 45140
Department of Medicine, Division of Cardiology and Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710
Vanderbilt University Medical Center, Nashville, Tennessee 37232-6300
^|| Genetics and Development, Columbia University, New York, New York 10032
^¶ Division of Urology, Department of Surgery, University of Nebraska Medical Center, Omaha, Nebraska 68198-2360
^** Myriad Pharmaceutics Inc., Salt Lake City, Utah 84108
Department of Radiation Oncology, Duke University Medical Center Durham, North Carolina 27710
Celgene Corporation, San Diego, California 92121

Abundant data now demonstrate that the growth of new blood vessels, termed angiogenesis, plays both pathological and beneficial roles in human disease. Based on these data, a tremendous effort has been undertaken to understand the molecular mechanisms that drive blood vessel growth in adult tissues. Tie2 recently was identified as a receptor tyrosine kinase expressed principally on vascular endothelium. Disrupting Tie2 function in mice resulted in embryonic lethality with defects in embryonic vasculature, suggesting a role in blood vessel maturation and maintenance. Based on these studies, we undertook a series of studies to probe the function of Tie2 in adult vasculature that will form the focus of this chapter. Consistent with a role in blood vessel growth in adult vasculature, Tie2 was upregulated and activated in the endothelium of rat ovary and in healing rat skin wounds, both areas of active angiogenesis. Moreover, Tie2 was upregulated in the endothelium of vascular "hot spots" in human breast cancer specimens. Surprisingly, Tie2 also was expressed and activated in the endothelium of all normal rat tissues examined, suggesting a role in maintenance of adult vasculature. To determine the functional role of Tie2 in tumor vasculature, a soluble Tie2 extracellular domain (ExTek) was designed that blocked the activation of Tie2 by its activating ligand, angiopoietin 1 (Ang1). Administration of recombinant ExTek protein or an ExTek adenovirus inhibited tumor growth and metastasis in rodent tumor models, demonstrating a functional role for Tie2 in pathological angiogenesis in adult tissues. To begin to understand the endothelial signaling pathways and cellular responses that mediate Tie2 function, we identified signaling molecules that are recruited to the activated, autophosphorylated Tie2 kinase domain. Two of these molecules, SHP2 and GRB2, are part of the pathway upstream of mitogen-activated protein kinase (MAPK) activation, a pathway that may be responsible for morphogenetic effects of Tie2 on endothelial cells. Another signaling molecule, p85, is responsible for recruitment of phosphatidylinositol 3 kinase (PI3-K) and activation of the Akt/PI3-K pathway. Akt/PI3-K has emerged as a critical pathway downstream of Tie2 that is necessary for cell survival effects as well as for chemotaxis, activation of endothelial nitric oxide synthase, and perhaps for anti-inflammatory effects of Tie2 activation. Taken together, these studies and many others demonstrate that the Tie2 pathway has important functions in adult tissues, in both quiescent vasculature and during angiogenesis, and help to validate the Tie2 pathway as a therapeutic target.

This article has been cited by other articles:

				Q.-h. Tuo, H. Zeng, A. Stinnett, H. Yu, J. L. Aschner, D.-F. Liao, and J.-X. Chen Critical role of angiopoietins/Tie-2 in hyperglycemic exacerbation of myocardial infarction and impaired angiogenesis Am J Physiol Heart Circ Physiol, June 1, 2008; 294(6): H2547 - H2557. [Abstract] [Full Text] [PDF]

				W. S. SHIN and S. G. ROCKSON Animal Models for the Molecular and Mechanistic Study of Lymphatic Biology and Disease Ann. N.Y. Acad. Sci., May 1, 2008; 1131(1): 50 - 74. [Abstract] [Full Text] [PDF]

				S. Rao, I. B. Lobov, J. E. Vallance, K. Tsujikawa, I. Shiojima, S. Akunuru, K. Walsh, L. E. Benjamin, and R. A. Lang Obligatory participation of macrophages in an angiopoietin 2-mediated cell death switch Development, December 15, 2007; 134(24): 4449 - 4458. [Abstract] [Full Text] [PDF]

				M. B. Marron, H. Singh, T. A. Tahir, J. Kavumkal, H.-Z. Kim, G. Y. Koh, and N. P. J. Brindle Regulated Proteolytic Processing of Tie1 Modulates Ligand Responsiveness of the Receptor-tyrosine Kinase Tie2 J. Biol. Chem., October 19, 2007; 282(42): 30509 - 30517. [Abstract] [Full Text] [PDF]

				H. T. Yuan, S. Venkatesha, B. Chan, U. Deutsch, T. Mammoto, V. P. Sukhatme, A. S. Woolf, and S. A. Karumanchi Activation of the orphan endothelial receptor Tie1 modifies Tie2-mediated intracellular signaling and cell survival FASEB J, October 1, 2007; 21(12): 3171 - 3183. [Abstract] [Full Text] [PDF]

				Y. Suarez, C. Fernandez-Hernando, J. S. Pober, and W. C. Sessa Dicer Dependent MicroRNAs Regulate Gene Expression and Functions in Human Endothelial Cells Circ. Res., April 27, 2007; 100(8): 1164 - 1173. [Abstract] [Full Text] [PDF]

				H. Kanazawa, S. Nomura, and K. Asai Roles of Angiopoietin-1 and Angiopoietin-2 on Airway Microvascular Permeability in Asthmatic Patients Chest, April 1, 2007; 131(4): 1035 - 1041. [Abstract] [Full Text] [PDF]

				C. Stocco, C. Telleria, and G. Gibori The Molecular Control of Corpus Luteum Formation, Function, and Regression Endocr. Rev., February 1, 2007; 28(1): 117 - 149. [Abstract] [Full Text] [PDF]

				S. Kanda, Y. Miyata, Y. Mochizuki, T. Matsuyama, and H. Kanetake Angiopoietin 1 Is Mitogenic for Cultured Endothelial Cells Cancer Res., August 1, 2005; 65(15): 6820 - 6827. [Abstract] [Full Text] [PDF]

				T. Tammela, A. Saaristo, M. Lohela, T. Morisada, J. Tornberg, C. Norrmen, Y. Oike, K. Pajusola, G. Thurston, T. Suda, et al. Angiopoietin-1 promotes lymphatic sprouting and hyperplasia Blood, June 15, 2005; 105(12): 4642 - 4648. [Abstract] [Full Text] [PDF]

				E.-H. Park, J. M. Lee, J. D. Blais, J. C. Bell, and J. Pelletier Internal Translation Initiation Mediated by the Angiogenic Factor Tie2 J. Biol. Chem., June 3, 2005; 280(22): 20945 - 20953. [Abstract] [Full Text] [PDF]

				P. Saharinen, K. Kerkela, N. Ekman, M. Marron, N. Brindle, G. M. Lee, H. Augustin, G. Y. Koh, and K. Alitalo Multiple angiopoietin recombinant proteins activate the Tie1 receptor tyrosine kinase and promote its interaction with Tie2 J. Cell Biol., April 25, 2005; 169(2): 239 - 243. [Abstract] [Full Text] [PDF]

				M. Kido, L. Du, C. C. Sullivan, R. Deutsch, S. W. Jamieson, and P. A. Thistlethwaite Gene transfer of a TIE2 receptor antagonist prevents pulmonary hypertension in rodents J. Thorac. Cardiovasc. Surg., February 1, 2005; 129(2): 268 - 276. [Abstract] [Full Text] [PDF]