BR22, a 26 kDa thyroid transcription factor-1 associated protein (TAP26), is expressed in human lung cells.
The current authors have previously identified BR22, a thyroid transcription factor (TTF)-1 associated protein 26 (TAP26), which interacts with TTF-1 to enhance human surfactant protein (SP)-B promoter activity in transfected 293 cells. However, the expression of TAP26 in the lung cells and its biological relevance to the SP-B production under physiological conditions were not examined. In this study, endogenous co-immunoprecipitation and in situ immunohistochemical staining techniques were employed to explore the presence of TAP26 and TTF-1 complex in the lung epithelial cells. The correlation of TAP26, TTF-1 and SP-B expression was inspected in H441 cells in the presence of dexamethasone, a known positive effector of the SP-B promoter. Monoclonal antibody (mAb) against TAP26 can co-immunoprecipitate both TAP26 and TTF-1 from H441 cells. Using this antibody in in situ staining of human lung sections, the data show that TAP26 is present in the lung alveolar epithelial cells. Reverse transcriptase-polymerase chain reaction and Western blot analyses of type-II cells as well as dexamethasone-treated H441 cells suggest that TAP26 expression is modulated coordinately with SP-B and TTF-1 in these cells. In summary, the current study demonstrates that thyroid transcription factor-1 associated protein 26 is an associated protein of thyroid transcription factor-1 in the lung alveolar epithelial cells where surfactant protein gene expressions take place in vivo.
Yang
M C W
MC
Dept of Internal Medicine, Pulmonary and Critical Care Medicine, UT Southwestern Medical Center, Dallas, TX 75390-9034, USA.
Wang
B
B
Weissler
J C
JC
Margraf
L R
LR
Yang
Y S
YS
D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D001483:Base Sequence; D015153:Blotting, Western; D004797:Enzyme-Linked Immunosorbent Assay; D005786:Gene Expression Regulation; D015723:Gene Library; D006801:Humans; D007124:Immunoenzyme Techniques; D051379:Mice; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000166:cytology / Q000378:metabolism*; D011663:Pulmonary Surfactants / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D000911:Antibodies, Monoclonal; C511144:CCDC59 protein, human; D009687:Nuclear Proteins; D011663:Pulmonary Surfactants; D014157:Transcription Factors