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Human Establishment Andor Maintenance of Cell Polarity

$122
20 µl
$303
100 µl
APPLICATIONS
REACTIVITY
Human

Application Methods: Western Blotting

Background: Rac and Cdc42 are members of the Rho-GTPase family. In mammals, Rac exists as three isoforms, Rac1, Rac2 and Rac3, which are highly similar in sequence. Rac1 and Cdc42, the most widely studied of this group, are ubiquitously expressed. Rac2 is expressed in cells of hematopoietic origin, and Rac3, while highly expressed in brain, is also found in many other tissues. Rac and Cdc42 play key signaling roles in cytoskeletal reorganization, membrane trafficking, transcriptional regulation, cell growth and development (1). GTP binding stimulates the activity of Rac/Cdc42, and the hydrolysis of GTP to GDP through the protein's intrinsic GTPase activity, rendering it inactive. GTP hydrolysis is aided by GTPase activating proteins (GAPs), while exchange of GDP for GTP is facilitated by guanine nucleotide exchange factors (GEFs). Another level of regulation is achieved through the binding of RhoGDI, a guanine nucleotide dissociation inhibitor, which retains Rho family GTPases, including Rac and Cdc42, in their inactive GDP-bound state (2,3).

$111
20 µl
$260
100 µl
APPLICATIONS
REACTIVITY
Human, Monkey, Mouse, Rat

Application Methods: Western Blotting

Background: Rac and Cdc42 are members of the Rho-GTPase family. In mammals, Rac exists as three isoforms, Rac1, Rac2 and Rac3, which are highly similar in sequence. Rac1 and Cdc42, the most widely studied of this group, are ubiquitously expressed. Rac2 is expressed in cells of hematopoietic origin, and Rac3, while highly expressed in brain, is also found in many other tissues. Rac and Cdc42 play key signaling roles in cytoskeletal reorganization, membrane trafficking, transcriptional regulation, cell growth and development (1). GTP binding stimulates the activity of Rac/Cdc42, and the hydrolysis of GTP to GDP through the protein's intrinsic GTPase activity, rendering it inactive. GTP hydrolysis is aided by GTPase activating proteins (GAPs), while exchange of GDP for GTP is facilitated by guanine nucleotide exchange factors (GEFs). Another level of regulation is achieved through the binding of RhoGDI, a guanine nucleotide dissociation inhibitor, which retains Rho family GTPases, including Rac and Cdc42, in their inactive GDP-bound state (2,3).

$759
30 rxns
1 Kit
The Active Cdc42 Detection Kit provides all reagents necessary for measuring activation of Cdc42 GTPase in the cell. GST-PAK1-PBD fusion protein is used to bind the activated form of GTP-bound Cdc42, which can then be immunoprecipitated with glutathione resin. Cdc42 activation levels are then determined by western blot using a Cdc42 Mouse mAb.
APPLICATIONS
REACTIVITY
Human, Mouse

Application Methods: Immunoprecipitation, Western Blotting

Background: The Ras superfamily of small GTP-binding proteins (G proteins) comprise a large class of proteins (over 150 members) that can be classified into at least five families based on their sequence and functional similarities: Ras, Rho, Rab, Arf, and Ran (1-3). These small G proteins have both GDP/GTP-binding and GTPase activities and function as binary switches in diverse cellular and developmental events that include cell cycle progression, cell survival, actin cytoskeletal organization, cell polarity and movement, and vesicular and nuclear transport (1). An upstream signal stimulates the dissociation of GDP from the GDP-bound form (inactive), which leads to the binding of GTP and formation of the GTP-bound form (active). The activated G protein then goes through a conformational change in its downstream effector-binding region, leading to the binding and regulation of downstream effectors. This activation can be switched off by the intrinsic GTPase activity, which hydrolyzes GTP to GDP and releases the downstream effectors. These intrinsic guanine nucleotide exchange and GTP hydrolysis activities of Ras superfamily proteins are also regulated by guanine nucleotide exchange factors (GEFs) that promote formation of the active GTP-bound form and GTPase activating proteins (GAPs) that return the GTPase to its GDP-bound inactive form (4).

$260
100 µl
APPLICATIONS
REACTIVITY
Bovine, Human, Monkey, Mouse, Rat

Application Methods: Western Blotting

Background: Rac and Cdc42 are members of the Rho-GTPase family. In mammals, Rac exists as three isoforms, Rac1, Rac2 and Rac3, which are highly similar in sequence. Rac1 and Cdc42, the most widely studied of this group, are ubiquitously expressed. Rac2 is expressed in cells of hematopoietic origin, and Rac3, while highly expressed in brain, is also found in many other tissues. Rac and Cdc42 play key signaling roles in cytoskeletal reorganization, membrane trafficking, transcriptional regulation, cell growth and development (1). GTP binding stimulates the activity of Rac/Cdc42, and the hydrolysis of GTP to GDP through the protein's intrinsic GTPase activity, rendering it inactive. GTP hydrolysis is aided by GTPase activating proteins (GAPs), while exchange of GDP for GTP is facilitated by guanine nucleotide exchange factors (GEFs). Another level of regulation is achieved through the binding of RhoGDI, a guanine nucleotide dissociation inhibitor, which retains Rho family GTPases, including Rac and Cdc42, in their inactive GDP-bound state (2,3).

$111
20 µl
$260
100 µl
APPLICATIONS
REACTIVITY
Bovine, Human, Mouse, Rat

Application Methods: Western Blotting

Background: Rac and Cdc42 are members of the Rho-GTPase family. In mammals, Rac exists as three isoforms, Rac1, Rac2 and Rac3, which are highly similar in sequence. Rac1 and Cdc42, the most widely studied of this group, are ubiquitously expressed. Rac2 is expressed in cells of hematopoietic origin, and Rac3, while highly expressed in brain, is also found in many other tissues. Rac and Cdc42 play key signaling roles in cytoskeletal reorganization, membrane trafficking, transcriptional regulation, cell growth and development (1). GTP binding stimulates the activity of Rac/Cdc42, and the hydrolysis of GTP to GDP through the protein's intrinsic GTPase activity, rendering it inactive. GTP hydrolysis is aided by GTPase activating proteins (GAPs), while exchange of GDP for GTP is facilitated by guanine nucleotide exchange factors (GEFs). Another level of regulation is achieved through the binding of RhoGDI, a guanine nucleotide dissociation inhibitor, which retains Rho family GTPases, including Rac and Cdc42, in their inactive GDP-bound state (2,3).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Monkey

Application Methods: Immunofluorescence (Immunocytochemistry), Western Blotting

Background: In Drosophila, lethal giant larvae (lgl), discs large (dlg), and scribble (scrib) act as tumor suppressor genes. Their loss of function in flies causes neoplastic overgrowth of larval brain tissue and imaginal epithelial cells hallmarked by disruption of the cytoskeletal network and cellular polarity (1,2). The human homolog of the Drosophila lgl protein, lethal giant larvae protein homolog 1(LLGL1), is a cytoskeletal protein implicated in regulating cellular organization, migration, and cell polarity (3). As in Drosophila, decreased expression of LLGL1 correlates with an increased incidence of cellular overgrowth and malignant transformation (4-6). In mammalian epithelial cells, LLGL1 redistributes from the cytoplasm to regions of cell-cell contact, allowing the establishment and maintainence of a polarized morphology (7). LLGL1 also plays a role in the formation of epithelial junctions via its direct interactions with PAR6 and aPKC, the latter of which has been shown to phosphorylate LLGL1 at Ser663, thus restricting its localization to the basolateral region of the cell (8). LLGL1 may also play an additional, unrealized role in cellular development and differentiation as indicated by the fact that Drosophila lgl has been implicated in controlling self-renewal and differentiation of progenitor cells (9). Recent studies in mice have suggested that a mammalian LLGL1 homolog that does not have tumor suppressor-like acitvity, LLGL2, is required for proper polarized invasion of trophoblasts and efficient branching morphogenesis during placental development (10).

$111
20 µl
$260
100 µl
APPLICATIONS
REACTIVITY
Human, Mouse, Rat

Application Methods: Immunofluorescence (Immunocytochemistry), Western Blotting

Background: Adherens junctions are dynamic structures that form cell-cell contacts and are important in development, differentiation, tissue integrity, morphology and cell polarity. They are composed of the transmembrane proteins, cadherins, which bind cadherins on adjacent cells in a calcium-dependent manner. On the cytoplasmic side of adherens junctions, the classic model states that cadherins are linked to the cytoskeleton through β- and α-catenin. α-E-catenin is ubiquitously expressed, α-N-catenin is expressed in neuronal tissue, and α-T-catenin is primarily expressed in heart tissue. Research studies have demonstrated that loss of E-cadherin and α-E-catenin occurs during the progression of several human cancers, indicating that the breakdown of adherens junctions is important in cancer progression (reviewed in 1).Research studies also suggest that, rather than acting as a static link between cadherins and actin, α-catenin regulates actin dynamics directly, possibly by competing with the actin nucleating arp2/3 complex (2,3). α-catenin also plays a role in regulating β-catenin-dependent transcriptional activity, affecting differentiation and response to Wnt signaling. α-catenin binds to β-catenin in the nucleus, preventing it from regulating transcription, and levels of both proteins appear to be regulated via proteasome-dependent degradation (4).

$111
20 µl
$260
100 µl
APPLICATIONS
REACTIVITY
Human, Monkey, Mouse

Application Methods: Immunoprecipitation, Western Blotting

Background: Adherens junctions are dynamic structures that form cell-cell contacts and are important in development, differentiation, tissue integrity, morphology and cell polarity. They are composed of the transmembrane proteins, cadherins, which bind cadherins on adjacent cells in a calcium-dependent manner. On the cytoplasmic side of adherens junctions, the classic model states that cadherins are linked to the cytoskeleton through β- and α-catenin. α-E-catenin is ubiquitously expressed, α-N-catenin is expressed in neuronal tissue, and α-T-catenin is primarily expressed in heart tissue. Research studies have demonstrated that loss of E-cadherin and α-E-catenin occurs during the progression of several human cancers, indicating that the breakdown of adherens junctions is important in cancer progression (reviewed in 1).Research studies also suggest that, rather than acting as a static link between cadherins and actin, α-catenin regulates actin dynamics directly, possibly by competing with the actin nucleating arp2/3 complex (2,3). α-catenin also plays a role in regulating β-catenin-dependent transcriptional activity, affecting differentiation and response to Wnt signaling. α-catenin binds to β-catenin in the nucleus, preventing it from regulating transcription, and levels of both proteins appear to be regulated via proteasome-dependent degradation (4).

$303
100 µl
APPLICATIONS
REACTIVITY
Human, Monkey, Mouse, Rat

Application Methods: Western Blotting

Background: Adherens junctions are dynamic structures that form cell-cell contacts and are important in development, differentiation, tissue integrity, morphology and cell polarity. They are composed of the transmembrane proteins, cadherins, which bind cadherins on adjacent cells in a calcium-dependent manner. On the cytoplasmic side of adherens junctions, the classic model states that cadherins are linked to the cytoskeleton through β- and α-catenin. α-E-catenin is ubiquitously expressed, α-N-catenin is expressed in neuronal tissue, and α-T-catenin is primarily expressed in heart tissue. Research studies have demonstrated that loss of E-cadherin and α-E-catenin occurs during the progression of several human cancers, indicating that the breakdown of adherens junctions is important in cancer progression (reviewed in 1).Research studies also suggest that, rather than acting as a static link between cadherins and actin, α-catenin regulates actin dynamics directly, possibly by competing with the actin nucleating arp2/3 complex (2,3). α-catenin also plays a role in regulating β-catenin-dependent transcriptional activity, affecting differentiation and response to Wnt signaling. α-catenin binds to β-catenin in the nucleus, preventing it from regulating transcription, and levels of both proteins appear to be regulated via proteasome-dependent degradation (4).

$303
100 µl
APPLICATIONS
REACTIVITY
Human, Monkey, Mouse, Rat

Application Methods: Immunoprecipitation, Western Blotting

Background: Adherens junctions are dynamic structures that form cell-cell contacts and are important in development, differentiation, tissue integrity, morphology and cell polarity. They are composed of the transmembrane proteins, cadherins, which bind cadherins on adjacent cells in a calcium-dependent manner. On the cytoplasmic side of adherens junctions, the classic model states that cadherins are linked to the cytoskeleton through β- and α-catenin. α-E-catenin is ubiquitously expressed, α-N-catenin is expressed in neuronal tissue, and α-T-catenin is primarily expressed in heart tissue. Research studies have demonstrated that loss of E-cadherin and α-E-catenin occurs during the progression of several human cancers, indicating that the breakdown of adherens junctions is important in cancer progression (reviewed in 1).Research studies also suggest that, rather than acting as a static link between cadherins and actin, α-catenin regulates actin dynamics directly, possibly by competing with the actin nucleating arp2/3 complex (2,3). α-catenin also plays a role in regulating β-catenin-dependent transcriptional activity, affecting differentiation and response to Wnt signaling. α-catenin binds to β-catenin in the nucleus, preventing it from regulating transcription, and levels of both proteins appear to be regulated via proteasome-dependent degradation (4).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Mouse, Rat

Application Methods: Immunofluorescence (Immunocytochemistry), Western Blotting

Background: Adherens junctions are dynamic structures that form cell-cell contacts and are important in development, differentiation, tissue integrity, morphology and cell polarity. They are composed of the transmembrane proteins, cadherins, which bind cadherins on adjacent cells in a calcium-dependent manner. On the cytoplasmic side of adherens junctions, the classic model states that cadherins are linked to the cytoskeleton through β- and α-catenin. α-E-catenin is ubiquitously expressed, α-N-catenin is expressed in neuronal tissue, and α-T-catenin is primarily expressed in heart tissue. Research studies have demonstrated that loss of E-cadherin and α-E-catenin occurs during the progression of several human cancers, indicating that the breakdown of adherens junctions is important in cancer progression (reviewed in 1).Research studies also suggest that, rather than acting as a static link between cadherins and actin, α-catenin regulates actin dynamics directly, possibly by competing with the actin nucleating arp2/3 complex (2,3). α-catenin also plays a role in regulating β-catenin-dependent transcriptional activity, affecting differentiation and response to Wnt signaling. α-catenin binds to β-catenin in the nucleus, preventing it from regulating transcription, and levels of both proteins appear to be regulated via proteasome-dependent degradation (4).

$111
20 µl
$260
100 µl
APPLICATIONS
REACTIVITY
D. melanogaster, Hamster, Human, Monkey, Mouse, Rat

Application Methods: Western Blotting

Background: Actin nucleation, the formation of new actin filaments from existing filaments, affects actin filament structure during cell motility, division, and intracellular trafficking. An important actin nucleation protein complex is the highly conserved ARP2/3 complex, consisting of ARP2, ARP3, and ARPC1-5. The ARP2/3 complex promotes branching of an existing actin filament and formation of a daughter filament following activation by nucleation-promoting factors, such as WASP/WAVE or cortactin (1). The formation of podosomes, small cellular projections that degrade the extracellular matrix, is enhanced by ARP2/3 complex action. ARP2/3 competes with caldesmon, an actin binding protein shown to negatively affect podosome formation (2). Along with N-WASP, the ARP2/3 complex regulates nuclear actin filament nucleation and controls actin polymerization during transcription (3).

$111
20 µl
$260
100 µl
APPLICATIONS
REACTIVITY
Human, Monkey

Application Methods: Western Blotting

Background: Actin nucleation, the formation of new actin filaments from existing filaments, affects actin filament structure during cell motility, division, and intracellular trafficking. An important actin nucleation protein complex is the highly conserved ARP2/3 complex, consisting of ARP2, ARP3, and ARPC1-5. The ARP2/3 complex promotes branching of an existing actin filament and formation of a daughter filament following activation by nucleation-promoting factors, such as WASP/WAVE or cortactin (1). The formation of podosomes, small cellular projections that degrade the extracellular matrix, is enhanced by ARP2/3 complex action. ARP2/3 competes with caldesmon, an actin binding protein shown to negatively affect podosome formation (2). Along with N-WASP, the ARP2/3 complex regulates nuclear actin filament nucleation and controls actin polymerization during transcription (3).

$260
100 µl
APPLICATIONS
REACTIVITY
Bovine, Human, Monkey, Mouse, Rat

Application Methods: Western Blotting

Background: Actin nucleation, the formation of new actin filaments from existing filaments, affects actin filament structure during cell motility, division, and intracellular trafficking. An important actin nucleation protein complex is the highly conserved ARP2/3 complex, consisting of ARP2, ARP3, and ARPC1-5. The ARP2/3 complex promotes branching of an existing actin filament and formation of a daughter filament following activation by nucleation-promoting factors, such as WASP/WAVE or cortactin (1). The formation of podosomes, small cellular projections that degrade the extracellular matrix, is enhanced by ARP2/3 complex action. ARP2/3 competes with caldesmon, an actin binding protein shown to negatively affect podosome formation (2). Along with N-WASP, the ARP2/3 complex regulates nuclear actin filament nucleation and controls actin polymerization during transcription (3).

$293
100 µl
APPLICATIONS
REACTIVITY
Dog, Human, Monkey, Mouse, Rat

Application Methods: Immunofluorescence (Immunocytochemistry), Immunoprecipitation, Western Blotting

Background: The extracellular matrix (ECM) is a complex structure of secreted macromolecules surrounding mammalian organs and tissues. Controlled interactions between cells and the ECM are important in proliferation, migration, survival, polarity, and differentiation. Cells contact the ECM primarily through heterodimeric integral membrane proteins called integrins. Integrins connect the ECM to the cytoskeleton, and therefore the cell signaling machinery, through protein complexes called focal adhesions (1).The ILK/PINCH/Parvin (IPP) complex is composed of three highly conserved proteins recruited to sites of ECM contact as pre-assembled structures. The IPP acts at the interface of the integrin/actin connection to regulate formation of focal adhesions and integrin signaling. All three proteins contain multiple protein binding domains allowing them to function as adaptor proteins in the formation of focal adhesions. ILK (integrin-linked kinase) also has a catalytic (protein Ser/Thr kinase) domain, and may or may not function as a kinase in vivo. Roles for IPP proteins outside of the IPP complex have been proposed, including regulation of gene expression (2,3).The parvin family consists of 3 members, α-parvin/actopaxin, β-parvin/affixin, and γ-parvin. α-parvin and β-parvin are expressed ubiquitously, while expression of γ-parvin is restricted to hematopoietic cells (4). α-parvin binds to f-actin both directly and via interaction with the focal adhesion protein paxillin (5). α-parvin regulates cell spreading and motility through interactions with the cofilin kinase TESK1 (6), and with the GTPase activating protein CdGAP (7). Phosphorylation of α-parvin during mitosis may have a role in the regulation of actin dynamics during the cell cycle (8).

$348
400 µl
This Cell Signaling Technology antibody is immobilized via covalent binding of primary amino groups to N-hydroxysuccinimide (NHS)-activated Sepharose® beads. α-Parvin (D7F9) XP® Rabbit mAb (Sepharose® Bead Conjugate) is useful for the immunoprecipitation of α-Parvin. The antibody is expected to exhibit the same species cross-reactivity as the unconjugated α-Parvin (D7F9) XP® Rabbit mAb #8190.
APPLICATIONS
REACTIVITY
Dog, Human, Monkey, Mouse, Rat

Application Methods: Immunoprecipitation

Background: The extracellular matrix (ECM) is a complex structure of secreted macromolecules surrounding mammalian organs and tissues. Controlled interactions between cells and the ECM are important in proliferation, migration, survival, polarity, and differentiation. Cells contact the ECM primarily through heterodimeric integral membrane proteins called integrins. Integrins connect the ECM to the cytoskeleton, and therefore the cell signaling machinery, through protein complexes called focal adhesions (1).The ILK/PINCH/Parvin (IPP) complex is composed of three highly conserved proteins recruited to sites of ECM contact as pre-assembled structures. The IPP acts at the interface of the integrin/actin connection to regulate formation of focal adhesions and integrin signaling. All three proteins contain multiple protein binding domains allowing them to function as adaptor proteins in the formation of focal adhesions. ILK (integrin-linked kinase) also has a catalytic (protein Ser/Thr kinase) domain, and may or may not function as a kinase in vivo. Roles for IPP proteins outside of the IPP complex have been proposed, including regulation of gene expression (2,3).The parvin family consists of 3 members, α-parvin/actopaxin, β-parvin/affixin, and γ-parvin. α-parvin and β-parvin are expressed ubiquitously, while expression of γ-parvin is restricted to hematopoietic cells (4). α-parvin binds to f-actin both directly and via interaction with the focal adhesion protein paxillin (5). α-parvin regulates cell spreading and motility through interactions with the cofilin kinase TESK1 (6), and with the GTPase activating protein CdGAP (7). Phosphorylation of α-parvin during mitosis may have a role in the regulation of actin dynamics during the cell cycle (8).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Monkey, Mouse, Rat

Application Methods: Western Blotting

Background: Microtubules (MTs) are polarized cellular filaments composed of α/β tubulin heterodimers. The slower growing (minus) microtubule ends are located at MT organizing centers (MTOCs), with the faster growing (plus) ends extending to the cell periphery. The regulation of MT dynamics is an important part of several biological processes, including cell division, migration, adhesion, membrane trafficking, and polarity (1).Human cytoplasmic linker-associate proteins 1 and 2 (CLASP1 and CLASP2) are evolutionarily conserved proteins that localize to the plus ends of interphase microtubules. During mitosis, CLASP 1 and CLASP2 localize to the centrosomes and kinetochores (KT) where they regulate mitotic spindle positioning to ensure proper chromosome alignment (2,3). Research studies indicate that phosphorylation of the carboxy terminus of CLASP2 during mitosis by CDK1 and PLK1 is required for efficient mitotic MT-KT attachment (4). Phosphorylation of CLASP2 at Ser1013 is a critical step that primes CLASP2 for further phosphorylation by PLK1 (4). The additional phosphorylation of CLASP2 at Ser533 and Ser537 by GSK3-3β controls the distribution of CLASP2 on MTs by inhibiting CLASP2 interaction with the Rac1/cdc42 effector protein IQGAP1 (5).

$260
100 µl
APPLICATIONS
REACTIVITY
Human, Mouse, Rat

Application Methods: Western Blotting

Background: Adenylyl cyclase-associated protein 1 (CAP1) is a widely expressed actin regulatory protein that plays a role in adhesion through its interactions with talin1 and FAK (1). High CAP1 expression is associated with metastasis in hepatocellular carcinoma (2), and esophageal squamous cell carcinoma (3). Research studies also show that CAP1 expression in human epithelial ovarian cancer correlates with proliferation, histological grade, and prognosis (4).

$260
100 µl
APPLICATIONS
REACTIVITY
Dog, Hamster, Human, Monkey, Mouse, Rat

Application Methods: Immunofluorescence (Immunocytochemistry), Western Blotting

Background: The extracellular matrix (ECM) is a complex structure of secreted macromolecules surrounding mammalian organs and tissues. Controlled interactions between cells and the ECM are important in proliferation, migration, survival, polarity, and differentiation. Cells contact the ECM primarily through heterodimeric integral membrane proteins called integrins. Integrins connect the ECM to the cytoskeleton, and therefore the cell signaling machinery, through protein complexes called focal adhesions (1).The ILK/PINCH/Parvin (IPP) complex is composed of three highly conserved proteins recruited to sites of ECM contact as pre-assembled structures. The IPP acts at the interface of the integrin/actin connection to regulate formation of focal adhesions and integrin signaling. All three proteins contain multiple protein binding domains allowing them to function as adaptor proteins in the formation of focal adhesions. ILK (integrin-linked kinase) also has a catalytic (protein Ser/Thr kinase) domain, and may or may not function as a kinase in vivo. Roles for IPP proteins outside of the IPP complex have been proposed, including regulation of gene expression (2,3).The parvin family consists of 3 members, α-parvin/actopaxin, β-parvin/affixin, and γ-parvin. α-parvin and β-parvin are expressed ubiquitously, while expression of γ-parvin is restricted to hematopoietic cells (4). α-parvin binds to f-actin both directly and via interaction with the focal adhesion protein paxillin (5). α-parvin regulates cell spreading and motility through interactions with the cofilin kinase TESK1 (6), and with the GTPase activating protein CdGAP (7). Phosphorylation of α-parvin during mitosis may have a role in the regulation of actin dynamics during the cell cycle (8).

$260
100 µl
APPLICATIONS
REACTIVITY
Bovine, Human

Application Methods: Immunoprecipitation, Western Blotting

Background: Tie2/Tek is a receptor tyrosine kinase (RTK) expressed almost exclusively on endothelial cells. It is critical for vasculogenesis and could be important for maintaining endothelial cell survival and integrity in adult blood vessels as well as tumor angiogenesis (1-3). A family of ligands known as the angiopoietins binds to Tie2. Interestingly, these ligands appear to have opposing actions; Angiopoietin-1 (Ang1) and Angiopoietin-4 (Ang4) stimulate tyrosine phosphorylation of Tie2; Angiopoietin-2 (Ang2) and Angiopoietin-3 (Ang3) can inhibit this phosphorylation (4,5). Downstream signaling components, including Grb2, Grb7, Grb14, SHP-2, the p85 subunit of phosphatidylinositol 3-kinase, and p56/Dok-2 interact with Tie2 in a phosphotyrosine-dependent manner through their SH2 or PTB domains (6,7). Tyr992 is located on the putative activation loop of Tie2 and is a major autophosphorylation site (8).