| 1. |
- de Miranda, Noel F. C. C., et al.
(författare)
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Transforming Growth Factor beta Signaling in Colorectal Cancer Cells With Microsatellite Instability Despite Biallelic Mutations in TGFBR2
- 2015
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Ingår i: Gastroenterology. - : Elsevier BV. - 0016-5085 .- 1528-0012. ; 148:7, s. 1427-1437.e8
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND & AIMS: Most colorectal cancer (CRC) cells with high levels of microsatellite instability (MSI-H) accumulate mutations at a microsatellite sequence in the gene encoding transforming growth factor beta receptor II (TGFBR2). TGF beta signaling therefore is believed to be defective in these tumors, although CRC cells with TGFBR2 mutations have been reported to remain sensitive to TGF beta. We investigated how TGF beta signaling might continue in MSI-H CRC cells. METHODS: We sequenced the 10-adenines microsatellite sequence in the TGFBR2 gene of 32 MSI-H colon cancer tissues and 6 cell lines (HCT116, LS180, LS411N, RKO, SW48, and SW837). Activation of TGF beta signaling was detected by SMAD2 phosphorylation and through use of a TGF beta-responsive reporter construct in all CRC cell lines. Transcripts of TGFBR2 were knocked-down in CRC cells using short hairpin RNA. Full-length and mutant forms of TGFBR2 were expressed in LS411N cells, which do not respond to TGF beta, and their activities were measured. RESULTS: SMAD2 was phosphorylated in most MSI-H CRC tissues (strong detection in 44% and weak detection in 34% of MSI-H tumors). Phosphorylation of SMAD2 in MSI-H cells required TGFBR2-even the form encoding a frameshift mutation. Transcription and translation of TGFBR2 with a 1-nucleotide deletion at its microsatellite sequence still produced a full-length TGFBR2 protein. However, protein expression required preservation of the TGFBR2 microsatellite sequence; cells in which this sequence was replaced with a synonymous nonmicrosatellite sequence did not produce functional TGFBR2 protein. CONCLUSION: TGF beta signaling remains active in some MSI-H CRC cells despite the presence of frameshift mutations in the TGFBR2 gene because the mutated gene still expresses a functional protein. Strategies to reactivate TGF beta signaling in colorectal tumors might not be warranted, and the functional effects of mutations at other regions of microsatellite instability should be evaluated.
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| 2. |
- van der Heide, Lars P., et al.
(författare)
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TGF beta Activates Mitogen- and Stress-activated Protein Kinase-1 (MSK1) to Attenuate Cell Death
- 2011
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 286:7, s. 5003-5011
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Tidskriftsartikel (refereegranskat)abstract
- Transforming growth factor-beta (TGF beta) binding to its receptor leads to intracellular phosphorylation of Smad2 and Smad3, which oligomerize with Smad4. These complexes accumulate in the nucleus and induce gene transcription. Here we describe mitogen-and stress-activated kinase 1 (MSK1) as an antagonist of TGF beta-induced cell death. Induction of MSK1 activity by TGF beta depends on Smad4 and p38 MAPK activation. Knockdown of GADD45, a Smad4-induced upstream regulator of p38 MAPK prevents TGF beta-induced p38 and MSK1 activity. MSK1 functionally regulates pro-apoptotic BH3-only BCL2 proteins, as MSK1 knockdown reduces Bad phosphorylation and enhances Noxa and Bim expression, leading to enhanced TGF beta-induced caspase-3 activity and cell death. This finding suggests that MSK1 represents a pro-survival pathway bifurcating downstream of p38 and antagonizes the established pro-apoptotic p38 MAPK function. Furthermore, EGF could reverse all the effects observed after MSK1 knockdown. Monitoring the status of MSK1 activity in cancer promises new therapeutic targets as inactivating both MSK1 and EGF signaling may (re)-sensitize cells to TGF beta-induced cell death.
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| 3. |
- Nakano, Naoko, et al.
(författare)
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TMED10 Protein Interferes with Transforming Growth Factor (TGF)-beta Signaling by Disrupting TGF-beta Receptor Complex Formation
- 2017
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Ingår i: Journal of Biological Chemistry. - : AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC. - 0021-9258 .- 1083-351X. ; 292:10, s. 4099-4112
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Tidskriftsartikel (refereegranskat)abstract
- The intensity and duration of TGF-beta signaling determine the cellular biological response. How this is negatively regulated is not well understood. Here, we identified a novel negative regulator of TGF-beta signaling, transmembrane p24-trafficking protein 10 (TMED10). TMED10 disrupts the complex formation between TGF-beta type I (also termed ALK5) and type II receptors (T beta RII). Misexpression studies revealed that TMED10 attenuated TGF-beta-mediated signaling. A 20-amino acid-long region from Thr(91) to Glu(110) within the extracellular region of TMED10 was found to be crucial for TMED 10 interaction with both ALK5 and T beta RII. Synthetic peptides corresponding to this region inhibit both TGF-beta-induced Smad2 phosphorylation and Smad-dependent transcriptional reporter activity. In a xenograft cancer model, where previously TGF-beta was shown to elicit tumor-promoting effects, gain-of-function and loss-of-function studies for TMED10 revealed a decrease and increase in the tumor size, respectively. Thus, we determined herein that TMED10 expression levels are the key determinant for efficiency of TGF-beta receptor complex formation and signaling.
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