Limits...
Oncogenic mutations of thyroid hormone receptor β.

Park JW, Zhao L, Willingham M, Cheng SY - Oncotarget (2015)

Bottom Line: Thus, these results argue against the oncogenic activity of PV being uniquely dependent on the PV mutated sequence.Rather, these four mutants could favor a C-terminal conformation that interacted with the CSH2 domain of p85α to initiate activation of PI3K to relay downstream signaling to promote tumorigenesis.Thus, we propose that the mutated C-terminal region of TRβ1 could function as an "onco-domain" and TRβ1 is a potential therapeutic target.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.

ABSTRACT
The C-terminal frame-shift mutant of the thyroid hormone receptor TRβ1, PV, functions as an oncogene. An important question is whether the oncogenic activity of mutated TRβ1 is uniquely dependent on the PV mutated sequence. Using four C-terminal frame-shift mutants-PV, Mkar, Mdbs, and AM-we examined that region in the oncogenic actions of TRβ1 mutants. Remarkably, these C-terminal mutants induced similar growth of tumors in mouse xenograft models. Molecular analyses showed that they physically interacted with the p85α regulatory subunit of PI3K similarly in cells. In vitro GST-binding assay showed that they bound to the C-terminal Src-homology 2 (CSH2) of p85α with markedly higher avidity. The sustained association of mutants with p85α led to activation of the common PI3K-AKT-ERK/STAT3 signaling to promote cell proliferation and invasion and to inhibit apoptosis. Thus, these results argue against the oncogenic activity of PV being uniquely dependent on the PV mutated sequence. Rather, these four mutants could favor a C-terminal conformation that interacted with the CSH2 domain of p85α to initiate activation of PI3K to relay downstream signaling to promote tumorigenesis. Thus, we propose that the mutated C-terminal region of TRβ1 could function as an "onco-domain" and TRβ1 is a potential therapeutic target.

No MeSH data available.


Related in: MedlinePlus

Establishment of cell lines stably expressing TRβ1 and the C-terminal mutants PV, Mkar, Mdbs, and AM in human MDA breast cancer cellsA. C-terminal amino acid sequences of TRβ1 and mutants PV, Mkar, Mdbs, and AM. Helix 11 and 12 boundaries are marked. The mutated amino acids are marked in bold. The mutated inserted nucleotides that lead to frame-shift mutations are shown. *Indicates the terminal amino acid. B. TRβ1 and mutants PV, Mkar, Mdbs, and AM were similarly expressed in MDA-MB-468 cells (lanes 2-6), but not in control MDA-MB-468 cells (lane 1). Western blot analysis was carried out as described in Materials and Methods. NS, non-specific bands.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4480739&req=5

Figure 1: Establishment of cell lines stably expressing TRβ1 and the C-terminal mutants PV, Mkar, Mdbs, and AM in human MDA breast cancer cellsA. C-terminal amino acid sequences of TRβ1 and mutants PV, Mkar, Mdbs, and AM. Helix 11 and 12 boundaries are marked. The mutated amino acids are marked in bold. The mutated inserted nucleotides that lead to frame-shift mutations are shown. *Indicates the terminal amino acid. B. TRβ1 and mutants PV, Mkar, Mdbs, and AM were similarly expressed in MDA-MB-468 cells (lanes 2-6), but not in control MDA-MB-468 cells (lane 1). Western blot analysis was carried out as described in Materials and Methods. NS, non-specific bands.

Mentions: The apriori findings raised a fundamental question as to whether the oncogenic action of a TRβ1 mutant is uniquely dependent on the PV mutated sequence or could extend to other C-terminal mutated sequences. The structure of the ligand-binding domain (LBD) of TRβ1 has been determined [19]. The C-terminal helixes 11 and 12 are critically involved in the structural changes of the LBD upon binding of T3 [20]. The frame-shift mutated sequence of PV is located in helix 12 (Figure 1). The availability of two naturally occurring mutants identified in RTH patients [21] has allowed us to evaluate whether other mutations in the C-terminal helix 11 and 12 could also exhibit oncogenic activity. The Mkar mutation has a T insertion at nucleotide 1590_1591 that leads to a frameshift mutation in the terminal 28 amino acids encompassing helix 11 and 12 (Figure 1A). The Mdbs mutation has a C insertion at nucleotide 1643_1644 that leads to a frameshift mutation in the C-terminal 10 amino acids located in helix 12. AM is a mutant that was constructed to combine the part of the mutation from Mkar (amino acids 436-446) and revert the distal amino acid sequence back to that of wild type TRβ1 (amino acids 447-461, located in helix 11) (Figure 1A) [21].


Oncogenic mutations of thyroid hormone receptor β.

Park JW, Zhao L, Willingham M, Cheng SY - Oncotarget (2015)

Establishment of cell lines stably expressing TRβ1 and the C-terminal mutants PV, Mkar, Mdbs, and AM in human MDA breast cancer cellsA. C-terminal amino acid sequences of TRβ1 and mutants PV, Mkar, Mdbs, and AM. Helix 11 and 12 boundaries are marked. The mutated amino acids are marked in bold. The mutated inserted nucleotides that lead to frame-shift mutations are shown. *Indicates the terminal amino acid. B. TRβ1 and mutants PV, Mkar, Mdbs, and AM were similarly expressed in MDA-MB-468 cells (lanes 2-6), but not in control MDA-MB-468 cells (lane 1). Western blot analysis was carried out as described in Materials and Methods. NS, non-specific bands.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4480739&req=5

Figure 1: Establishment of cell lines stably expressing TRβ1 and the C-terminal mutants PV, Mkar, Mdbs, and AM in human MDA breast cancer cellsA. C-terminal amino acid sequences of TRβ1 and mutants PV, Mkar, Mdbs, and AM. Helix 11 and 12 boundaries are marked. The mutated amino acids are marked in bold. The mutated inserted nucleotides that lead to frame-shift mutations are shown. *Indicates the terminal amino acid. B. TRβ1 and mutants PV, Mkar, Mdbs, and AM were similarly expressed in MDA-MB-468 cells (lanes 2-6), but not in control MDA-MB-468 cells (lane 1). Western blot analysis was carried out as described in Materials and Methods. NS, non-specific bands.
Mentions: The apriori findings raised a fundamental question as to whether the oncogenic action of a TRβ1 mutant is uniquely dependent on the PV mutated sequence or could extend to other C-terminal mutated sequences. The structure of the ligand-binding domain (LBD) of TRβ1 has been determined [19]. The C-terminal helixes 11 and 12 are critically involved in the structural changes of the LBD upon binding of T3 [20]. The frame-shift mutated sequence of PV is located in helix 12 (Figure 1). The availability of two naturally occurring mutants identified in RTH patients [21] has allowed us to evaluate whether other mutations in the C-terminal helix 11 and 12 could also exhibit oncogenic activity. The Mkar mutation has a T insertion at nucleotide 1590_1591 that leads to a frameshift mutation in the terminal 28 amino acids encompassing helix 11 and 12 (Figure 1A). The Mdbs mutation has a C insertion at nucleotide 1643_1644 that leads to a frameshift mutation in the C-terminal 10 amino acids located in helix 12. AM is a mutant that was constructed to combine the part of the mutation from Mkar (amino acids 436-446) and revert the distal amino acid sequence back to that of wild type TRβ1 (amino acids 447-461, located in helix 11) (Figure 1A) [21].

Bottom Line: Thus, these results argue against the oncogenic activity of PV being uniquely dependent on the PV mutated sequence.Rather, these four mutants could favor a C-terminal conformation that interacted with the CSH2 domain of p85α to initiate activation of PI3K to relay downstream signaling to promote tumorigenesis.Thus, we propose that the mutated C-terminal region of TRβ1 could function as an "onco-domain" and TRβ1 is a potential therapeutic target.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.

ABSTRACT
The C-terminal frame-shift mutant of the thyroid hormone receptor TRβ1, PV, functions as an oncogene. An important question is whether the oncogenic activity of mutated TRβ1 is uniquely dependent on the PV mutated sequence. Using four C-terminal frame-shift mutants-PV, Mkar, Mdbs, and AM-we examined that region in the oncogenic actions of TRβ1 mutants. Remarkably, these C-terminal mutants induced similar growth of tumors in mouse xenograft models. Molecular analyses showed that they physically interacted with the p85α regulatory subunit of PI3K similarly in cells. In vitro GST-binding assay showed that they bound to the C-terminal Src-homology 2 (CSH2) of p85α with markedly higher avidity. The sustained association of mutants with p85α led to activation of the common PI3K-AKT-ERK/STAT3 signaling to promote cell proliferation and invasion and to inhibit apoptosis. Thus, these results argue against the oncogenic activity of PV being uniquely dependent on the PV mutated sequence. Rather, these four mutants could favor a C-terminal conformation that interacted with the CSH2 domain of p85α to initiate activation of PI3K to relay downstream signaling to promote tumorigenesis. Thus, we propose that the mutated C-terminal region of TRβ1 could function as an "onco-domain" and TRβ1 is a potential therapeutic target.

No MeSH data available.


Related in: MedlinePlus