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TGFbeta1 activates c-Jun and Erk1 via alphaVbeta6 integrin.

Luettich K, Schmidt C - Mol. Cancer (2003)

Bottom Line: Overexpression of alphaVbeta6 integrin is associated with lymph node metastasis of gastric carcinomas.We conclude that TGFbeta1 activates c-Jun via the MEKK1/p38 MAP kinase pathway and influences cytoskeletal organization.These finding may provide a link between TGFbeta1 and the metastatic behavior of cancers.

View Article: PubMed Central - HTML - PubMed

Affiliation: 1Department of Dermatology, Weill Medical College of Cornell University, 1300 York Avenue, New York, New York, 10021, USA. karsta.luettich@molecular-cancer.org

ABSTRACT
Transforming growth factor beta (TGFbeta) plays an important role in animal development and many cellular processes. A variety of cellular functions that are required for tumor metastasis are controlled by integrins, a family of cell adhesion receptors. Overexpression of alphaVbeta6 integrin is associated with lymph node metastasis of gastric carcinomas. It has been demonstrated that a full TGFbeta1 signal requires both alphaVbeta6 integrin and SMAD pathway. TGFbeta1 binds to alphaVbeta6 via the DLXXL motif, a freely accessible amino acid sequence in the mature form of TGFbeta1. Binding of mature TGFbeta1 to alphaVbeta6 leads to immobilization and tyrosine phosphorylation of proteins, which are associated with focal adhesions, a hallmark of integrin-mediated signal transduction. Here, we show that binding of mature TGFbeta1 recruits the mitogen-activated protein kinase kinase kinase 1 (MEKK1), a mediator of c-Jun activation, and the extracellular signaling-regulated kinase-1 (Erk1) to focal adhesions. In addition, the p21-activated kinase 1 (PAK1) is associated with focal adhesions and differentially phosphorylated upon TGFbeta1 stimulation. We conclude that TGFbeta1 activates c-Jun via the MEKK1/p38 MAP kinase pathway and influences cytoskeletal organization. These finding may provide a link between TGFbeta1 and the metastatic behavior of cancers.

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MEKK1 is associated with focal adhesions. BxPC-3 cells were stimulated with 10 nM of mature TGFβ1 for ten minutes followed by preparation of the Triton-X100 nonsoluble fraction and precipitation with αVβ6 integrin antibodies. The precipitate was then re-precipitated with anti-FAK antibodies (sc-1688) and analyzed with a MEKK1 antibody (sc-448). In part, the cells were preincubated with a TGFβ1 antibody [10].
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Figure 4: MEKK1 is associated with focal adhesions. BxPC-3 cells were stimulated with 10 nM of mature TGFβ1 for ten minutes followed by preparation of the Triton-X100 nonsoluble fraction and precipitation with αVβ6 integrin antibodies. The precipitate was then re-precipitated with anti-FAK antibodies (sc-1688) and analyzed with a MEKK1 antibody (sc-448). In part, the cells were preincubated with a TGFβ1 antibody [10].

Mentions: Reorganization of the cytoarchitecture regulates signaling pathways including the mobilization of intracellular calcium, activation of tyrosine kinases, Ras, extracellular signal-regulated kinase (ERK), and c-Jun NH2-terminal kinase (JNK). Consistent with the activation of signaling pathways, specific transcription factors are activated by cytoskeletal restructuring [10,11,17]. We stimulated BxPC-3 cells with 10 nM of mature TGFβ1, prepared the Triton-X100 nonsuluble fraction, precipitated with αVβ6 integrin antibodies followed by re-precipitation with FAK antibodies. Our assays revealed that MEKK1 and c-Jun are phosphorylated and associated with focal adhesions after stimulation of BxPC-3 cells with mature TGFβ1 (Figures 3 and 4). Our findings are in part supported by Verrecchia et al showing that TGFβ induces c-Jun and JunB [22]. In addition, our finding that MEKK1 associates with focal adhesions finds support in the report from Cuevas et al [23]. Cuevas et al show evidence that MEKK1 colocalizes with focal adhesions in adhering MEKK1-/- fibroblasts reconstituted with EGFP-MEKK1 [23]. However, this is the first report that c-Jun is associated with the cytoskeleton, whilst phosphorylated.


TGFbeta1 activates c-Jun and Erk1 via alphaVbeta6 integrin.

Luettich K, Schmidt C - Mol. Cancer (2003)

MEKK1 is associated with focal adhesions. BxPC-3 cells were stimulated with 10 nM of mature TGFβ1 for ten minutes followed by preparation of the Triton-X100 nonsoluble fraction and precipitation with αVβ6 integrin antibodies. The precipitate was then re-precipitated with anti-FAK antibodies (sc-1688) and analyzed with a MEKK1 antibody (sc-448). In part, the cells were preincubated with a TGFβ1 antibody [10].
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC222989&req=5

Figure 4: MEKK1 is associated with focal adhesions. BxPC-3 cells were stimulated with 10 nM of mature TGFβ1 for ten minutes followed by preparation of the Triton-X100 nonsoluble fraction and precipitation with αVβ6 integrin antibodies. The precipitate was then re-precipitated with anti-FAK antibodies (sc-1688) and analyzed with a MEKK1 antibody (sc-448). In part, the cells were preincubated with a TGFβ1 antibody [10].
Mentions: Reorganization of the cytoarchitecture regulates signaling pathways including the mobilization of intracellular calcium, activation of tyrosine kinases, Ras, extracellular signal-regulated kinase (ERK), and c-Jun NH2-terminal kinase (JNK). Consistent with the activation of signaling pathways, specific transcription factors are activated by cytoskeletal restructuring [10,11,17]. We stimulated BxPC-3 cells with 10 nM of mature TGFβ1, prepared the Triton-X100 nonsuluble fraction, precipitated with αVβ6 integrin antibodies followed by re-precipitation with FAK antibodies. Our assays revealed that MEKK1 and c-Jun are phosphorylated and associated with focal adhesions after stimulation of BxPC-3 cells with mature TGFβ1 (Figures 3 and 4). Our findings are in part supported by Verrecchia et al showing that TGFβ induces c-Jun and JunB [22]. In addition, our finding that MEKK1 associates with focal adhesions finds support in the report from Cuevas et al [23]. Cuevas et al show evidence that MEKK1 colocalizes with focal adhesions in adhering MEKK1-/- fibroblasts reconstituted with EGFP-MEKK1 [23]. However, this is the first report that c-Jun is associated with the cytoskeleton, whilst phosphorylated.

Bottom Line: Overexpression of alphaVbeta6 integrin is associated with lymph node metastasis of gastric carcinomas.We conclude that TGFbeta1 activates c-Jun via the MEKK1/p38 MAP kinase pathway and influences cytoskeletal organization.These finding may provide a link between TGFbeta1 and the metastatic behavior of cancers.

View Article: PubMed Central - HTML - PubMed

Affiliation: 1Department of Dermatology, Weill Medical College of Cornell University, 1300 York Avenue, New York, New York, 10021, USA. karsta.luettich@molecular-cancer.org

ABSTRACT
Transforming growth factor beta (TGFbeta) plays an important role in animal development and many cellular processes. A variety of cellular functions that are required for tumor metastasis are controlled by integrins, a family of cell adhesion receptors. Overexpression of alphaVbeta6 integrin is associated with lymph node metastasis of gastric carcinomas. It has been demonstrated that a full TGFbeta1 signal requires both alphaVbeta6 integrin and SMAD pathway. TGFbeta1 binds to alphaVbeta6 via the DLXXL motif, a freely accessible amino acid sequence in the mature form of TGFbeta1. Binding of mature TGFbeta1 to alphaVbeta6 leads to immobilization and tyrosine phosphorylation of proteins, which are associated with focal adhesions, a hallmark of integrin-mediated signal transduction. Here, we show that binding of mature TGFbeta1 recruits the mitogen-activated protein kinase kinase kinase 1 (MEKK1), a mediator of c-Jun activation, and the extracellular signaling-regulated kinase-1 (Erk1) to focal adhesions. In addition, the p21-activated kinase 1 (PAK1) is associated with focal adhesions and differentially phosphorylated upon TGFbeta1 stimulation. We conclude that TGFbeta1 activates c-Jun via the MEKK1/p38 MAP kinase pathway and influences cytoskeletal organization. These finding may provide a link between TGFbeta1 and the metastatic behavior of cancers.

Show MeSH
Related in: MedlinePlus