Characterization of novel transforming growth factor-beta type I receptors found in malignant pleural effusion tumor cells.
BACKGROUND
Tumors expressing a transforming growth factor-beta type I receptor (T beta RI) mutant with sequence deletions in a nine-alanine (9A) stretch of the signal peptide are reported to be highly associated with disease progression. Expression of this mutant could interfere with endogenous TGFbeta signaling in the cell. However, little is known about the importance of the remaining part of the signal peptide on the cellular function of T beta RI.


RESULTS
We cloned and identified four new in-frame deletion variants of T beta RI, designated DM1 to DM4, in pleural effusion-derived tumor cells. Intriguingly, DM1 and DM2, with a small region truncated in the putative signal peptide of T beta RI, had a serious defect in their protein expression compared with that of the wild-type receptor. Using serial deletion mutagenesis, we characterized a region encoded by nucleotides 16-51 as a key element controlling T beta RI protein expression. Consistently, both DM1 and DM2 have this peptide deleted. Experiments using cycloheximde and MG132 further confirmed its indispensable role for the protein stability of T beta RI. In contrast, truncation of the 9A-stretch itself or a region downstream to the stretch barely affected T beta RI expression. However, variants lacking a region C-terminal to the stretch completely lost their capability to conduct TGFbeta-induced transcriptional activation. Intriguingly, expression of DM3 in a cell sensitive to TGFbeta made it significantly refractory to TGFbeta-mediated growth inhibition. The effect of DM3 was to ablate the apoptotic event induced by TGFbeta.


CONCLUSIONS
We identified four new transcript variants of T beta RI in malignant effusion tumor cells and characterized two key elements controlling its protein stability and transcriptional activation. Expression of one of variants bestowed cancer cells with a growth advantage in the presence of TGFbeta. These results highlight the potential roles of some naturally occurring T beta RI variants on the promotion of tumor malignancy.
Chen
Kuo-Li
KL
Graduate Institute of Life Sciences, National Defense Medical Center, Taipei 114, Taiwan. corry@nhri.org.tw
Liu
Wan-Hsin
WH
Yang
Yi-Yuan
YY
Leu
Sy-Jye C
SJ
Shih
Neng-Yao
NY
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D049109:Cell Proliferation; D002478:Cells, Cultured; D006801:Humans; D008969:Molecular Sequence Data; D016066:Pleural Effusion, Malignant / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D021382:Protein Sorting Signals; D012334:RNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D000077293:Receptor, Transforming Growth Factor-beta Type I; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism
D020033:Protein Isoforms; D021382:Protein Sorting Signals; D012334:RNA, Neoplasm; D018125:Receptors, Transforming Growth Factor beta; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I
Lung Cancer. 2003 Jun;40(3):281-7
12781426
Chest. 2002 Oct;122(4):1421-7
12377874
Respirology. 2003 Sep;8(3):321-5
12911825
Nature. 2003 Oct 9;425(6958):577-84
14534577
J Clin Oncol. 2004 Feb 15;22(4):756-8
14966109
Cancer Detect Prev. 2004;28(1):57-64
15041079
Cell. 1989 Mar 24;56(6):1019-32
2538246
Nucleic Acids Res. 1991 May 25;19(10):2785
1645866
Chest. 1991 Aug;100(2):429-38
1650680
FEBS Lett. 1993 Jun 21;324(3):345-8
8405379
J Biol Chem. 1993 Oct 25;268(30):22215-8
7693660
Genes Dev. 1994 Mar 15;8(6):720-31
7926762
Mol Cell Biol. 1995 Oct;15(10):5339-45
7565683
J Biol Chem. 1996 Feb 2;271(5):2769-75
8576253
Proc Natl Acad Sci U S A. 1996 Oct 29;93(22):12142-9
8901547
Protein Eng. 1997 Jan;10(1):1-6
9051728
Proc Natl Acad Sci U S A. 1997 May 27;94(11):5877-81
9159168
EMBO J. 1997 Jul 1;16(13):3912-23
9233801
Genomics. 1997 Dec 1;46(2):278-83
9417915
Clin Cancer Res. 1996 Aug;2(8):1255-61
9816295
Am J Physiol. 1999 Jan;276(1 Pt 2):F88-95
9887084
Int J Cancer. 1999 Jul 2;82(1):43-51
10360819
Science. 1999 Oct 8;286(5438):312-5
10514378
Prostate Cancer Prostatic Dis. 2005;8(1):50-3
15505640
Gynecol Oncol. 2005 May;97(2):543-9
15863158
JAMA. 2005 Oct 5;294(13):1634-46
16204663
Annu Rev Cell Dev Biol. 2005;21:659-93
16212511
J Clin Oncol. 2005 Oct 20;23(30):7743-4; author reply 7744-6
16234535
Proc Natl Acad Sci U S A. 2006 Feb 28;103(9):3078-83
16492767
Cancer Res. 1999 Nov 15;59(22):5678-82
10582683
N Engl J Med. 2000 May 4;342(18):1350-8
10793168
Bioessays. 2000 Sep;22(9):790-802
10944581
Cancer Res. 2000 Aug 15;60(16):4507-12
10969799
Hum Mol Genet. 2000 Sep 22;9(15):2297-304
11001933
Cancer Res. 2001 Jun 15;61(12):4679-82
11406536
Nat Genet. 2001 Oct;29(2):117-29
11586292
Proc Natl Acad Sci U S A. 2001 Dec 4;98(25):14687-92
11717408
Genes Chromosomes Cancer. 2001 Dec;32(4):381-3
11746979
Cancer Epidemiol Biomarkers Prev. 2002 Feb;11(2):211-4
11867510
Arch Biochem Biophys. 2003 Jul 1;415(1):1-5
12801506