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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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Pak1 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 reprecipitated with anti-FAK antibodies (sc-1688), followed by re-precipitation with anti-phosphoS (ab9334, Abcam), anti-phosphoThr (ab2286), and analyzed with a Pak1 antibody (71-9300, Zymed). In part, the cells were preincubated with 50 μM PP2 (Calbiochem), and 50 μM PD98059 (Calbiochem), respectively [10].
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Figure 6: Pak1 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 reprecipitated with anti-FAK antibodies (sc-1688), followed by re-precipitation with anti-phosphoS (ab9334, Abcam), anti-phosphoThr (ab2286), and analyzed with a Pak1 antibody (71-9300, Zymed). In part, the cells were preincubated with 50 μM PP2 (Calbiochem), and 50 μM PD98059 (Calbiochem), respectively [10].

Mentions: We found that Pak1 is associated with focal adhesions upon stimulation of BxPC-3 cells with 10 nM of mature TGFβ1 (Figure 6). The Src family kinase inhibitor 4-amino-5-(4-chloro-phenyl)-7-(t-butyl)pyrazolo- [3,4-d]-pyrimidine (PP2) significantly reduced the phosphorylation level of Pak1 compared with the MEK1 inhibitor PD98059. The effect of the MEK1 inhibitor on the Pak1 phosphorylation is striking because Pak1 is considered upstream of MEK1/Erk [39]. It is possible that other signaling molecules mediate a crosstalk between the two pathways. Notably, the src-inhibitor PP2 partially reduced the Pak1 phosphorylation level. Blocking of Pak activity is considered a so called "signal therapy for Ras-induced cancers" [40,41].


TGFbeta1 activates c-Jun and Erk1 via alphaVbeta6 integrin.

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

Pak1 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 reprecipitated with anti-FAK antibodies (sc-1688), followed by re-precipitation with anti-phosphoS (ab9334, Abcam), anti-phosphoThr (ab2286), and analyzed with a Pak1 antibody (71-9300, Zymed). In part, the cells were preincubated with 50 μM PP2 (Calbiochem), and 50 μM PD98059 (Calbiochem), respectively [10].
© Copyright Policy
Related In: Results  -  Collection

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

Figure 6: Pak1 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 reprecipitated with anti-FAK antibodies (sc-1688), followed by re-precipitation with anti-phosphoS (ab9334, Abcam), anti-phosphoThr (ab2286), and analyzed with a Pak1 antibody (71-9300, Zymed). In part, the cells were preincubated with 50 μM PP2 (Calbiochem), and 50 μM PD98059 (Calbiochem), respectively [10].
Mentions: We found that Pak1 is associated with focal adhesions upon stimulation of BxPC-3 cells with 10 nM of mature TGFβ1 (Figure 6). The Src family kinase inhibitor 4-amino-5-(4-chloro-phenyl)-7-(t-butyl)pyrazolo- [3,4-d]-pyrimidine (PP2) significantly reduced the phosphorylation level of Pak1 compared with the MEK1 inhibitor PD98059. The effect of the MEK1 inhibitor on the Pak1 phosphorylation is striking because Pak1 is considered upstream of MEK1/Erk [39]. It is possible that other signaling molecules mediate a crosstalk between the two pathways. Notably, the src-inhibitor PP2 partially reduced the Pak1 phosphorylation level. Blocking of Pak activity is considered a so called "signal therapy for Ras-induced cancers" [40,41].

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