在血管生成的過程當中，初級的管狀結構(endothelial tube)形成除了需要內皮細胞(endothelial cell)之外，尚須具有外被細胞(pericyte)或是平滑肌細胞(smooth muscle cell)聚集，才能形成一個初級的血管 。而內皮細胞被認為在徵召(recruit)外被細胞或平滑肌細胞聚集的過程當中，扮演著重要的角色。在 Vikkula et al.這篇文獻當中報導，在兩個具有遺傳性靜脈形成不良(venous malformation)的家族當中，Tie2受器的第849個胺基酸由精胺酸(arginine)突變為色胺酸(tryptophan)。此單一胺基酸突變導致Tie2 (R849W)受器表現過活化(constitutive activation)的現象；意即Tie2受器可以不需要其配體存在(ligand-independent)就可以被活化。靜脈形成不良的病人，其靜脈周圍的平滑肌細胞層出現厚度不一的缺陷，且通常在皮膚造成類似血管瘤的斑記(birth mark)。本研究主要的目的，即是以此疾病為研究模式，釐清內皮細胞如何透過Tie2受器與其配體，血管生長素-1 (angiopoietin-1)，去影響及調節周邊的平滑肌細胞，進而影響血管的發育。本研究中，首先利用酵母菌雙雜合系統(yeast-two hybrid system)，篩選出可以與Tie2受器結合的結合蛋白(binding proteins)，並進一步瞭解這些蛋白在Tie2訊息傳導路徑所扮演的角色。利用此系統，我們已經從內皮細胞的cDNA基因庫(cDNA library)篩選出四個結合蛋白，這些蛋白與Tie2受器在細胞內的交互作用也利用免疫共沈澱(co-immunoprecipitation)的方式證明。利用穩定性轉染(stable transfection)的方式，我們已經成功建立穩定表達 Ang1的細胞株，並可進一步從這些細胞株收集含有Ang1的條件培養基(conditioned medium)進行後續的研究。為了研究內皮細胞與平滑肌細胞之間的交互作用，我們採用內皮/平滑肌細胞共同培養(EC/SMC co-culture)的方式進行。利用貼塊法(explants method)，我們成功從人類臍帶分離出平滑肌細胞，更進一步利用表現正常或是突變Tie2蛋白的內皮細胞與平滑肌細胞共同培養，以瞭解是否此突變對內皮細胞徵召平滑肌細胞的能力有所影響。在共同培養下，內皮細胞產生平行排列狀的型態轉變，且其VE-cadherin表現量下降。此外， transforming growth factor (TGF-β)及 platelet-derived growth factor (PDGF-BB)兩個生長因子在共同培養的內皮細胞中也產生減少的現象。然而當比較表現正常或突變Tie2蛋白的內皮細胞，卻發現了先前所觀察到的TGF-β及PDGF-BB基因變化必須仰賴Tie2激酶活性，並且在平滑肌細胞存在與否情況下，Tie2激酶活性也扮演不同的調控角色。但在目前所得到的結果中，這樣的變化對於內皮細胞徵召平滑肌細胞的能力並無顯著影響。雖然需要更多實驗來證明Tie2如何調控內皮細胞與平滑肌細胞間交互作用，目前結果顯示PDGF-BB似乎是受到Tie2調控的重要因子。

　　The formation of endothelial cell (EC) tubes requires the recruitment of pericytes or smooth muscle cells (SMCs). ECs are believed to play an important role in this recruitment event. In the paper by Vikkula et al., venous malformation, a disease that leads to variable thickness of SMCs, was mapped to the receptor tyrosine kinase with immunoglobulin and epidermal growth factor homology domains 2 (Tie2) where an arginine-to-tryptophan substitution (R849W) results in ligand-independent activation of Tie2. By using VMs as a disease model, the specific aim of this study is to delineate how the Tie2 and its ligand, Ang1, regulate the SMCs surrounding the ECs and subsequently modulate vessel maturation. We utilized yeast two hybrid approach to investigate possible molecules that might be involved in this signaling pathway. Four putative interacting proteins were identified by screening an endothelial cDNA library. Among these four proteins, two of them were previously identified to be associated with Tie2, and the remaining two were confirmed to interact with Tie2 in vivo using co-immunoprecipitation. Ang1-expressing stable cell clones were established to produce Ang1-containing conditioned medium. Also, we have successfully established primary culture of SMCs from human umbilical arteries. SMCs were further co-cultured with either wild type or mutant Tie2-expressing ECs to elucidate whether signaling of Tie2 mutant (R849W) would influence the recruitment of SMCs to ECs by evaluating the migration ability of SMC. Under co-culturing condition, we found ECs became elongated and parallelly aligned, and expressed less VE-cadherin than ECs alone. The mRNA level of PDGF-BB and TGF-β of co-cultured ECs were both down-regulated. When we over-expressed normal and mutant Tie2 in the co-cultured ECs, the down-regulation of PDGF-BB and TGF-β appeared to require a functional kinase activity of Tie2. Moreover, we observed that the kinase activity of Tie2 played different roles in mediating the expression of PDGF-BB in the presence or absence of SMCs. However, when we compared the number of recruited SMCs by ECs overexpressing normal or mutated Tie2, there was no significant difference among them. Although more studies are needed to clarify how Tie2 modulate the cross-talk between ECs and SMCs, the present findings suggest that PDGF-BB might be a crucial molecule involved in Tie2 signaling in the vessel maturation.

1. Vikkula, M., Boon, L.M., Carraway III, K.L., Calvert, J.T., Diamonti,
A.J. Goumnerov, B., Pasyk, K.A., Marchuk, D.A., Warman, M.L., Cantley,
L.C., Mulliken, J.B., and Osen, B.R., 1996. Vascular dysmorphogenesis
caused by an activating mutation in the receptor tyrosine kinase TIE2.
Cell 87, 1181-1190.
2. Risau, W., and Lemmom, V., 1988. Changes in the vascular extracellular
matrix during embryonic vasculogenesis and angiogenesis. Dev. Biol. 125,
441-450.
3. Risau, W., Sariola, H., Zerwes, H.G., Sasse, J., Ekblom, P., Kelmer, R.,
and Doetschman, T., 1988. Vasculogenesis and andiogenesis on
embryonic-stem-cell-derived embryoid bodies. Development 102, 471-478.
4. Noden, D.M., 1989. Embryonic origins and assembly of blood vessels. Am.
Rev. Respir. Dis. 140, 1097-1103.
5. Ferra, N., 2002. VEGF and the quest for tumor angiogenesis factors. Nat.
Cancer. Rev. 2, 795-803.
6. Nagy, J.A. et al., 2002. VEGF-A induces angiogenesis, arteriogenesis,
lymphangiogenesis, and vascular formations. Cold Spring Harbor Symposium
on Quantitative Biology 67, 227-237.
7. Shalaby, F., Rossant, J., Yamaguchi, T.P., Gertenstein, M., Wu, X-F.,
Breitman, M.L., and Schuh, A.C., 1995. Failure of blood-island formation
and vasculogenesis in Flk-1-deficient mice. Nature 376, 62-66.
8. Fong, G-H., Rossant, J., Gertenstein, M., and Breitman, M.l., 1995. Role
of Flt-1 receptor tyrosine kinase in regulating assembly of vascular
endothelium. Nature 376, 66-70.
9. Carmeliet, P., Ferrara, V., Breier, G., Pollefeyt, S., Kieckens, L.,
Gertsenstein, M.Fahrig, M., Vandenhoeck, A., Harpal, K.Eberhardt, C.,
Declercq, C., Pawling, J., Moons, L., Collen, D., Risau, W., and Nagy,
A., 1996. Abnormal blood vessel development and lethality in embryos
lacking a single VEGF allele. Nature 380, 435-439.
10. Ferrara, N., Carver-Moore, K., Chen, H., Dowd, M., Lu, L., O’Shea, K.S.,
Powell, L., Hillan, K.J., and Moore, M.W., 1996. Heterozygous embryonic
lethality induced by targeted inactivation of the VEGF gene. Nature 380,
439-442.
11. Janes, R.K., 2003. Molecular regulation of vessel maturation. Nat Med. 9,
685-93. Review.
12. Dumont, D.J., Yamaguchi, T.P., Conlon, R.A., Rossant, J., Breitman, M.L.,
1992. Tek, novel tyrosine kinase gene located on mouse chromosome 4, is
expressed in endothelial cells and their presumptive precursors. Oncogene
7, 1471-1480.
13. Iwama, A., Hamaguchi, I., Hashiyama, M., Murayama, Y., Yasunaga, K.,
Suda, T., 1993. Molecular cloning and characterization of mouse Tie and
Tek receptor tyrosine kinase genes and their expression in hematopoietic
stem cells. Biochem. Biophys. Res. Commun. 195, 301-309
14. Davis, S., Aldrich, T.H., Jones, P.F. et al., 1996. Isolation of
angiopoietin- 1, a ligand for the TIE2 receptor, by secretion-trap
expression cloning. Cell 87, 1161-1169.
15. Sato, T.N., Qin, Y., Kozak, C.A., Audus, K.L., 1993. tie-1 and tie-2
define another class of putative receptor tyrosine kinase genes expressed
in early embryonic vascular system. Proc. Natl. Acad. Sci. USA 90,
9355-9358
16. Dumont, D.J., Gradwohl, G.J., Fong, G.-H., Auerbach, R., Breitman, M.L.,
1993. The endothelial-specific receptor tyrosine kinase, tek, is a member
of a new subfamily of receptors. Oncogene 8, 1293-1301.
17. Partanen, J., Armstrong, E., Makela, T.P. et al., 1992. A novel
endothelial cell surface receptor tyrosine kinase with extracellular
epidermal growth factor homology domains. Mol. Cell. Biol. 12, 1698-1707.
18. Dumont, D.J., Fong, G.-H., Puri, M.C., Gradwohl, G., Alitalo, K.,
Breitman, M.L., 1995. Vascularization of the mouse embryo: a study of
flk-1, tek, tie, and vascular endothelial growth factor expression during
development. Dev. Dyn. 203, 80-92.
19. Korhonen, J., Polvi, A., Partanen, J., Alitalo, K., 1994. The mouse tie
receptor tyrosine kinase gene: expression during embryonic angiogenesis.
Oncogene 9, 395-403.
20. Korhonen, J., Lahtinen, I., Halmekyto, M. et al., 1995.
Endothelial-specific gene expression directed by the tie gene promoter in
vivo. Blood 86, 1828-1835.
21. Dumont, D.J., Gradwohl, G., Fong, G.-H. et al., 1994. Dominantnegative
and targeted null mutations in the endothelial receptor tyrosine kinase,
tek, reveal a critical role in vasculogenesis of the embryo. Genes Dev.
8, 1897-1909.
22. Sato, T.N., Tozawa, Y., Deutsch, U. et al., 1995. Distinct roles of the
receptor tyrosine kinases Tie-1 and Tie-2 in blood vessel formation.
Nature 376, 70-74.
23. Patan, S., 1998. TIE1 and TIE2 receptor tyrosine kinases inversely
regulate embryonic angiogenesis by the mechanism of intussusceptive
microvascular growth. Microvasc. Res. 56, 1-21.
24. Puri, M.C., Partanen, J., Rossant, J., Bernstein, A., 1999. Interaction
of the TEK and TIE receptor tyrosine kinases during cardiovascular
development. Development 126, 4569-4580.
25. Puri, M.C., Rossant, J., Alitalo, K., Bernstein, A., Partanen, J., 1995.
The receptor tyrosine kinase TIE is required for integrity and survival
of vascular endothelial cells. EMBO J. 14, 5884-5891.
26. Kukk, E. et al., 1997. Analysis of Tie receptor tyrosine kinase in
haemopoietic progenitor and leukaemia cells. Br. J. Haematol. 98,
195-203.
27. Iwama, A. et al., 1993. Molecular cloning and characterization of mouse
TIE and TEK receptor tyrosine kinase genes and their expression in
hematopoietic stem cells. Biochem. Biophys. Res. Commun. 195, 301-309.
28. Maisonpierre, P.C., Suri, C., Jones, P.F. et al., 1997. Angiopoietin-2, a
natural antagonist for Tie2 that disrupts in vivo angiogenesis. Science
277, 55-60.
29. Valenzuela, D.M., Griffiths, J.A., Rojas, J. et al., 1999. Angiopoietins
3 and 4: diverging gene counterparts in mice and humans. Proc. Natl.
Acad. Sci. USA 96, 1904-1909.
30. Witzenbichler, B., Maisonpierre, P.C., Jones, P., Yancopoulos, G.D.,
Isner J.M., 1998. Chemotactic properties of angiopoietin-1 and -2,
ligands for the endothelial-specific receptor tyrosine kinase Tie2. J
Biol Chem. 273, 18514-18521.
31. Koblizek, T.I., Weiss, C., Yancopoulos, G.D., Deutsch, U., Risau, W.,
1998. Angiopoietin-1 induces sprouting angiogenesis in vitro. Curr Biol.
8, 529 -532.
32. Fujikawa K., de Aos Scherpenseel, I., Jain, S.K., Presman, E.,
Christensen, R.A., Varticovski, L., 1999. Role of PI 3-kinase in
angiopoietin-1–mediated migration and attachment-dependent survival of
endothelial cells. Exp Cell Res. 253, 663-672.
33. Suri, C., Jones, P.F., Patan, S. et al., 1996. Requisite role of
angiopoietin-1, a ligand for the TIE2 receptor, during embryonic
angiogenesis. Cell 87, 1171-1180.
34. Witzenbichler, B., Maisonpierre, P.C., Jones, P., Yancopoulos, G.D. and
Isner, J.M., 1998. Chemotactic propertites of angiopoietin-1 and -2,
ligands for the endothelial-specific receptor tyrosine kinase Tie2. J.
Biol. Chem. 273, 18514 -18521
35. Kim, I., Kim, H.G., So, J.N., Kim, J.H., Kwak, H.J., Koh, G.Y., 2000.
Angiopoietin-1 regulates endothelial cell survival through the
phosphatidylinositol 3--kinase-Akt signal transduction pathway. Circ.
Res. 86, 24-29.
36. Papapetropoulos, A., Fulton, D., Mahboubi, K. et al., 2000.
Angiopoietin-1 inhibits endothelial cell apoptosis via the Akt-survivin
pathway. J. Biol. Chem. 275, 9102-9105.
37. Witzenbichler, B., Maisonpierre, P.C., Jones, P., Yancopoulos, G.D. and
Isner, J.M., 1998. Chemotactic propertites of angiopoietin-1 and -2,
ligands for the endothelial-specific receptor tyrosine kinase Tie2. J.
Biol. Chem. 273, 18514 -18521.
38. Fujikawa, K., de Aos Scherpenseel, I., Jain, S.K., Presman, E.,
Christensen, R.A., Varticovski, L., 1999. Role of PI 3-kinase in
angiopoietin-1-mediated migration and attachment-dependent survival of
endothelial cells. Exp. Cell Res. 253, 663-672.
39. Kim, I., Kim, H.G., So, J.N., Kim, J.H., Kwak, H.J., Koh, G.Y., 2000.
Angiopoietin-1 regulates endothelial cell survival through the
phosphatidylinositol 3--kinase-Akt signal transduction pathway. Circ.
Res. 86, 24-29.
40. Kim I., Kim, H.G., Moon, S.O., Chae, S.W., So, J.N., Koh, K.N., Ahn, BC,
Koh, G.Y., 2000. Angiopoietin-1 induces endothelial cell sprouting
through the activation of focal adhesion kinase and plasmin secretion.
Circ Res 86, 952-959.
41. Jones, N., Master, Z., Jones, J., Bouchard, D., Gunji, Y., Sasaki, H.,
Daly, R., Alitalo, K., Dumont, D.J., 1999. Identification of Tek/Tie2
binding partners. Binding to a multifunctional docking site mediates cell
survival and migration. J Biol Chem 274 30896-30905.
42. Kontos, C.D., Stauffer, T.P., Yang, W.P. et al., 1998. Tyrosine 1101 of
Tie2 is the major site of association of p85 and is required for
activation of phosphatidylinositol 3-kinase and Akt. Mol. Cell. Biol. 18,
4131-4140.
43. Ward, N.L., Dumont, D.J., 2002. The angiopoietins and Tie2/Tek: adding to
the complexity of cardiovascular development. Semin Cell Dev Biol. 13,
19-27.
44. Jones, N., Chen, S.H., Sturk, C., Master, Z., Tran, J., Kerbel, R.S.,
Dumont D.J., 2003. A unique autophosphorylation site on Tie2/Tek mediates
Dok-R phosphotyrosine binding domain binding and function. Mol Cell Biol.
23, 2658-68.
45. Master, Z., Jones, N., Tran, J., Kerbel, S., Dumont, D.J., 2001. Dok-R
plays a pivotal role in angiopoietin-1 mediated cell migration through
activation of Pak. EMBO J. 20, 5919-5928.
46. Jones, N., Dumont, D.J., 1998. The Tek-Tie2 receptor signals through a
novel Dok-related docking protein, Dok-R. Oncogene 17, 1097-1108.
47. Jones, N., Master, Z., Jones, J. et al., 1999. Identification of Tek-Tie2
binding partners. Binding to a multifunctional docking site mediates cell
survival and migration. J. Biol. Chem. 274, 30896-30905.
48. Hughes, D.P., Marron, M.B., Brindle, N.P., 2003. The antiinflammatory
endothelial tyrosine kinase Tie2 interacts with a novel nuclear
factor-κB inhibitor ABIN-2. Circ Res. 92, 630-636.
49. Tadros A., Hughes, D.P., Dunmore, B.J., and Brindle, N.P. 2003. ABIN-2
protects endothelial cells from death and has a role in the antiapoptotic
effect of angiopoietin-1. Blood. 102, 4407-4409.
50. Mulliken, J. B., Young, A. E. (eds.), 1988. Vascular Birthmarks:
Hemangiomas and Vascular Malformations. Philadelphia: W. B. Saunders Co.
51. Boon, L.M., Mulliken, J.B., Vikkula, M., Watkins, H., Salic, A., Seidman,
J., Olsen, B.R., Warman, M.L., 1994. Assignment of a locus for dominantly
inherited venous malformations to chromosome 9p. Hum. Mol. Genet. 3,
1583-1587.
52. Gallione, C.J., Pasyk, K.A., Boon, L.M., et al., 1995. A gene for
familial venous malformations maps to chromosome 9p in a second large
kindred. J. Med. Genet. 32, 197-199.
53. Kluk, M.J., Comont, C., Wu, M.T., and Hla, T., 2003. Platelet-derived
growth factor (PDGF)-induced chemotaxis does not require the
G-protein-coupled receptor S1P1 in murine embryonic fibroblasts and
vascular smooth muscle cells. FEBS Lett. 533, 25-28.
54. Hellstrom, M. et al., 2001. Lack of pericytes leads to endothelial
hyperplasia and abnormal vascular morphogenesis. J. Cell Biol. 153,
543-553.
55. Hiroaki Yoshida, M.N., Shinji Makita, Katsuhiko Hiramori. 1996. Paracrine
effect of human vascular endothelial cells on human vascular smooth
muscle cell proliferation: Transmembrane co-culture method. Heart
Vessels. 11,229-233.
56. Nunes, I M.J., Happel, J.G. 1996. Structure and activation of the large
latent transforming growth factor-beta complex. Int J obes Relat Metab
Disord. 20, S4–S8.
57. Davies, P.F., Kerr, C., 1982. Co-cultivation of vascular endothelial and
smooth muscle cells using microcarrier techniques. Exp. Cell Res. 141,
455-459.
58. Davies, P.F., Truskey, G.A., Warren, H.B., O’Connor, S.E., Eisenhaure,
B.H., 1985. Metabolic cooperation between vascular endothelial cells and
smooth muscle cells in coculture: Changes in low density lipoprotein
metabolism. J. Cell Biol. 101, 871-879.
59. Davies, P.F., Olesen, S.P., Clapham, Davies, P., 1986. Biology of disease
vascular cell interactions with special reference to the pathogenesis of
atherosclerosis. Lab Inves. 55, 5-24.
60. Powell, R.J., Carruth, J.A., Basson, M.D., Bloodgood, R., Sumpio, B.E.,
1996. Matrix-specific effect of endothelial control of smooth muscle cell
migration. J. Vasc. Surg. 24, 51-57.
61. Fillinger, M.F., Sampson, L.N., Cronenwett, J.L., Powell, R.J., Wagner,
R.J., 1997. Coculture of endothelial cells and smooth muscle cells in
bilayer and conditioned media models. J. Surg. Res. 67, 169-178.
62. van Buul-Wortelboer, M.F., Brinkman, H.J., Dingemans, K.P., de Groot,
P.G., van Aken, W.G., van Mourik, J.A., 1986. Reconstitution of the
vascular wall in vitro. A novel model to study interactions between
endothelial and smooth muscle cells. Exp. Cell Res. 162, 151-158.
63. Saunders, K.B., D’Amore, P.A., 1992. An in vitro model for cell-cell
interactions. In Vitro Cell Dev. Biol. 28A, 521-528.
64. Fillinger, M.F., O’Connor, S.E., Wagner, R.J., Cronenwett, J.L., 1993.
The effect of endothelial cell coculture on smooth muscle cell
proliferation. J. Vasc. Surg. 17, 1058-1067, Discussion 1067-1068.
65. Powell, R.J., Carruth, J.A., Basson, M.D., Bloodgood, R., Sumpio, B.E.,
1996. Matrix-specific effect of endothelial control of smooth muscle cell
migration. J. Vasc. Surg. 24, 51-57.
66. Jones, P.A., 1979. Construction of an arterial blood vessel wall from
cultured endothelial and smooth muscle cells. Proc. Natl. Acad. Sci. USA.
76, 1882-1886.
67. Merrilees, M.J., Scott, L., 1981. Interaction of aortic endothelial and
smooth muscle cells in culture. Effect on glycosaminoglycan levels.
Atherosclerosis 39, 147-161.
68. Hirschi, K.K., Rohovsky, S.A., D’Amore, P.A., 1998. PDGF, TGF-beta, and
heterotypic cell-cell interactions mediate endothelial cell-induced
recruitment of 10T1/2 cells and their differentiation to a smooth muscle
fate. J. Cell Biol. 141, 805-814.
69. van Buul-Wortelboer, M.F., Brinkman, H.J., Dingemans, K.P., de Groot,
P.G., van Aken, W.G., van Mourik, J.A., 1986. Reconstitution of the
vascular wall in vitro. A novel model to study interactions between
endothelial and smooth muscle cells. Exp. Cell Res. 162, 151-158.
70. Ziegler, T., Alexander, R.W., Nerem, R.M., 1995. An endothelial
cell-smooth muscle cell co-culture model for use in the investigation of
flow effects on vascular biology. Ann. Biomed. Eng. 23, 216-225.
71. Kurzen, H., Manns, S., Dandekar, G., Schmidt, T., Prätzel, S., Kräling,
B.M., 2002. Tightening of endothelial cell contacts: a physiologic
response to cocultures with smooth-muscle-like 10T1/2 cells. J. Invest.
Dermatol. 119, 143-53.
72. Bussolino, F., Di Renzo, M.F., Ziche, M., Bocchietto, E., Olivero, M.,
Naldini, L., Gaudino, G., Tamagnone, L., Coffer, A., and Comoglio, P.M.,
1992. Hepatocyte growth factor is a potent angiogenic factor which
stimulates endothelial cell motility and growth. J. Cell Biol. 119,
629-641.
73. Morgan, D.L., 1996. Isolation and culture of human umbilical vein
endothelial cells. In: Methods in Molecular Medicine: Human Cell Culture
Protocols (Jones, G.E., ed.), Humana Press Inc., Totowa, NJ, pp. 101-109.
74. Sambrook, J., Fritsch, E.F., and Maniatis, T., 1989. Molecular Cloning: A
Laboratory Manual. Cold Spring Harbor Laboratory Press, Cold Spring
Harbor, NY.
75. Skalli, O., Rppraz, P., Trzeciak, A., Benzonana, G., Gillessen, D., and
Gabbiani, G., 1986. A monoclonal antibody against α-smooth muscle actin.
J. Cell. Biol. 103, 2787-2796.
76. Thberg, J., Nilsson, J., Palmberg, L., and Sjolund, M., 1985. Adult human
arterial smooth muscles in primary culture. Modulation from contractile
to synthetic phonotype. Cell Tissue Res. 239, 69-74.
77. Heydarkhan-Hagvall, S., Helenius, G., Johansson, B.R., Li, J.Y.,
Mattsson, E., Risberg, B., 2003. Co-culture of endothelial cells and
smooth muscle cells affects gene expression of angiogenic factors. J Cell
Biochem. 89, 1250-1259.
78. Shewchuk, L.M., Hassell, A.M., Ellis, B., Holmes, W.D., Davis, R., Horne,
E.L., Kadwell, S.H., McKee, D.D., Moore, J.T., 2000. Structure of the
Tie2 RTK domain: self-inhibition by the nucleotide binding loop,
activation loop, and C-terminal tail. Structure Fold Des. 8, 1105-1113.
79. Niu, X.L., Peters, K.G., Kontos, C.D., 2002. Deletion of the carboxyl
terminus of Tie2 enhances kinase activity, signaling, and function.
Evidence for an autoinhibitory mechanism. J. Biol. Chem. 277,
31768-31773.
80. Asada, H., Ishii, N., Sasaki, Y., Endo, K., Kasai, H., Tanaka, N.,
Takeshita, T., Tsuchiya, S., Konno, T., Sugamura, K., 1999. Grf40, A
novel Grb2 family member, is involved in T cell signaling through
interaction with SLP-76 and LAT. J. Exp. Med. 189, 1383-1390.
81. Zadeh, G., Qian, B., Okhowat, A., Sabha, N., Kontos,, C.D., Guha, A.,
2004. Targeting the Tie2/Tek receptor in astrocytomas. Am. J. Pathol.
164, 467-76.
82. Cucina, A., Borrelli, V., Randone, B., Coluccia, P., Sapienza, P.,
Cavallaro, A., 2003. Vascular endothelial growth factor increases the
migration and proliferation of smooth muscle cells through the mediation
of growth factors released by endothelial cells. J. Surg. Res. 109,
16-23.
83. Nishishita, T., Lin, P.C., 2004. Angiopoietin 1, PDGF-B, and TGF-beta
gene regulation in endothelial cell and smooth muscle cell interaction.
J. Cell. Biochem. 91, 584-593.