Bombesin Receptor‐Activated Protein (BRAP) Modulates NF‐κB Activation in Bronchial Epithelial Cells by Enhancing HDAC Activity

Abstract

Our previous studies provided evidence that bombesin receptor-activated protein (BRAP), encoded by C6ORF89, is widely expressed in human airway epithelial cells and may play a role in the stress response of lung epithelia. In this study, we demonstrated that BRAP has a regulatory effect on NF-κB transcriptional activity in cultured human bronchial epithelial cells (HBECs). BRAP overexpression by gene transfer inhibited both basal and inducible NF-κB transcriptional activity in HBECs, whereas BRAP knockdown had the opposite effect. BRAP was shown to regulate NF-κB activity by enhancing histone deacetylase (HDAC) activity. In addition, BRAP might increase HDAC activity that leads to NF-κB activation via its putative C-terminal domain. Our study suggests that the BRAP protein is an important regulator of immune and inflammatory responses in the human airway epithelium.

Lack of bombesin receptor–activated protein attenuates bleomycin-induced pulmonary fibrosis in mice

“…In our previous study ( Liu et al, 2016 ), we found that down-regulation of BRAP expression by siRNA gene silencing enhanced nuclear factor-kappa B (NF-κB) transcriptional activity in cultured human bronchial cell line 16HBE14o-. Therefore, we sought to examine whether BRAP homologous protein in mouse lung fibroblasts has the regulatory effect on NF-κB pathway because NF-κB is also among the key regulators of fibroblast functions.…”

“…After fixation in 4% paraformaldehyde, the lung tissues were embedded in paraffin ( Liu et al, 2016 ) and tissue sections of 3 μm thick were prepared for further analysis. Hematoxylin-eosin (H&E), Masson’s trichrome, and Sirius Red staining ( Rittie, 2017 ) were conducted by Wuhan Saville Biotechnology.…”

“…The severity of lung fibrosis was evaluated by the Ashcroft scale analysis ( Wang et al, 2021 ). Immunohistochemistry analysis was performed according to the method described previously ( Liu et al, 2016 ). Tissue sections were deparaffinized, hydrated, and subjected to antigenic retrieval by incubation with Tris–EDTA Buffer (10 mM TrisBase, 1 mM EDTA Solution, and 0.05% Tween 20, pH 9.0) at 98°C for 20 min.…”

“…It is encoded by human C6orf89 gene and contains 354 amino acids. It was predicated to be a type II membrane protein with a putative N-terminal transmembrane (TM) domain ( Lalioti et al, 2013 ) and a potential catalytic region within its C terminus ( Liu et al, 2016 ). It is expressed in several cell types including bronchial epithelial cells, macrophages and neurons with functions that are still poorly characterized (data not shown).…”

“…It is expressed in several cell types including bronchial epithelial cells, macrophages and neurons with functions that are still poorly characterized (data not shown). The overexpression of this protein in a cultured immortalized human bronchial epithelial cell line 16HBE14o- was found to promote proliferation of the cells and be involved in regulating transcriptional activity of NF-κB in those cells ( Liu et al, 2016 ). In an attempt to further investigate the biological role of BRAP, we constructed a gene knockout mouse BC004004 −/− that lacks the expression of the homologous protein of BRAP which is encoded by the mouse gene BC004004 .…”