CBAP functions as a novel component in chemokine-induced ZAP70-mediated T-cell adhesion and migration

CBAP regulates the function of Akt-associated TSC protein complexes to modulate mTORC1 signaling

The Akt-Rheb-mTORC1 pathway plays a crucial role in regulating cell growth, but the mechanisms underlying the activation of Rheb-mTORC1 by Akt remain unclear. In our previous study, we found that CBAP was highly expressed in human T-ALL cells and primary tumors, and its deficiency led to reduced phosphorylation of TSC2/S6K1 signaling proteins as well as impaired cell proliferation and leukemogenicity. We also demonstrated that CBAP was required for Akt-mediated TSC2 phosphorylation in vitro. In response to insulin, CBAP was also necessary for the phosphorylation of TSC2/S6K1 and the dissociation of TSC2 from the lysosomal membrane. Here we report that CBAP interacts with AKT and TSC2, and knockout of CBAP or serum starvation leads to an increase in TSC1 in the Akt/TSC2 immunoprecipitation complexes. Lysosomal-anchored CBAP was found to override serum starvation and promote S6K1 and 4EBP1 phosphorylation and c-Myc expression in a TSC2-dependent manner. Additionally, recombinant CBAP inhibited the GAP activity of TSC2 complexes in vitro, leading to increased Rheb-GTP loading, likely due to the competition between TSC1 and CBAP for binding to the HBD domain of TSC2. Overexpression of the N26 region of CBAP, which is crucial for binding to TSC2, resulted in a decrease in mTORC1 signaling and an increase in TSC1 association with the TSC2/AKT complex, ultimately leading to increased GAP activity toward Rheb and impaired cell proliferation. Thus, we propose that CBAP can modulate the stability of TSC1-TSC2 as well as promote the translocation of TSC1/TSC2 complexes away from lysosomes to regulate Rheb-mTORC1 signaling.

Overexpression of transmembrane protein 102 implicates poor prognosis and chemoresistance in epithelial ovarian carcinoma patients

Most ovarian cancer patients experience disease recurrence and chemotherapeutic resistance, and the underlying mechanisms are unclear. Identifying relevant pathways could reveal new therapeutic targets. Here we examined expression of transmembrane protein 102 (TMEM102), a biomarker of prognosis and chemoresistance, in epithelial ovarian cancer (EOC), and assessed its role in inhibiting tumor cell apoptosis. We performed qRT-PCR to investigate the association of TMEM102 expression with clinical outcomes in 226 EOC patients. We also conducted in vitro studies to explore possible mechanisms through which TMEM102 may influence chemoresistance, including the effects of downregulating TMEM102 expression with small interfering RNA. Serous and high-grade carcinomas expressed significantly higher TMEM102 than normal ovarian tissues. TMEM102 was also overexpressed in patients with advanced-stage disease and chemoresistance. Reduction of TMEM102 expression by small interfering RNA induced ovarian cancer cell apoptosis after cytotoxic treatment. TMEM102 overexpression enhanced chemoresistance via upregulation of heat shock proteins 27, 60, and 70; and survivin, resulting in decreased cytochrome c in the mitochondria and decreased caspase 9 expression. Our results indicate that TMEM102 overexpression may promote chemoresistance via inhibition of a mitochondria-associated apoptotic pathway.

CBAP modulates Akt-dependent TSC2 phosphorylation to promote Rheb-mTORC1 signaling and growth of T-cell acute lymphoblastic leukemia

High-frequency relapse remains a clinical hurdle for complete remission of T-cell acute lymphoblastic leukemia (T-ALL) patients, with heterogeneous dysregulated signaling profiles—including of Raf-MEK-ERK and Akt-mTORC1-S6K signaling pathways—recently being implicated in disease outcomes. Here we report that GM-CSF/IL-3/IL-5 receptor common β-chain-associated protein (CBAP) is highly expressed in human T-ALL cell lines and many primary tumor tissues and is required to bolster leukemia cell proliferation in tissue culture and for in vivo leukemogenesis in a xenograft mouse model. Downregulation of CBAP markedly restrains expansion of leukemia cells and alleviates disease aggravation of leukemic mice. Transcriptomic profiling and molecular biological analyses suggest that CBAP acts upstream of Ras and Rac1, and functions as a modulator of both Raf-MEK–ERK and Akt-mTORC1 signaling pathways to control leukemia cell growth. Specifically, CBAP facilitated Akt-dependent TSC2 phosphorylation in cell-based assays and in vitro analysis, decreased lysosomal localization of TSC2, and elevated Rheb-GTP loading and subsequent activation of mTORC1 signaling. Taken together, our findings reveal a novel oncogenic contribution of CBAP in T-ALL leukemic cells, in addition to its original pro-apoptotic function in cytokine-dependent cell lines and primary hematopoietic cells, by demonstrating its functional role in the regulation of Akt-TSC2-mTORC1 signaling for leukemia cell proliferation. Thus, CBAP represents a novel therapeutic target for many types of cancers and metabolic diseases linked to PI3K-Akt-mTORC1 signaling.

Molecular association of CD98, CD29, and CD147 critically mediates monocytic U937 cell adhesion

Adhesion events of monocytes represent an important step in inflammatory responses induced by chemokines. The β1-integrin CD29 is a major adhesion molecule regulating leukocyte migration and extravasation. Although several adhesion molecules have been known as regulators of CD29, the molecular interactions between CD29 and its regulatory adhesion molecules (such as CD98 and CD147) have not been fully elucidated. Therefore, in this study, we examined whether these molecules are functionally, biochemically, and cell-biologically associated using monocytic U937 cells treated with aggregation-stimulating and blocking antibodies, as well as enzyme inhibitors. The surface levels of CD29, CD98, and CD147 (but not CD43, CD44, and CD82) were increased. The activation of CD29, CD98, and CD147 by ligation of them with aggregation-activating antibodies triggered the induction of cell-cell adhesion, and sensitivity to various enzyme inhibitors and aggregation-blocking antibodies was similar for CD29-, CD98-, and CD147-induced U937 cell aggregation. Molecular association between these molecules and the actin cytoskeleton was confirmed by confocal microscopy and immunoprecipitation. These results strongly suggest that CD29 might be modulated by its biochemical and cellular regulators, including CD98 and CD147, via the actin cytoskeleton.

CBAP promotes thymocyte negative selection by facilitating T-cell receptor proximal signaling

T-cell receptor (TCR)-transduced signaling is critical to thymocyte development at the CD4/CD8 double-positive stage, but the molecules involved in this process are not yet fully characterized. We previously demonstrated that GM-CSF/IL-3/IL-5 receptor common β-chain-associated protein (CBAP) modulates ZAP70-mediated T-cell migration and adhesion. On the basis of the high expression of CBAP during thymocyte development, we investigated the function of CBAP in thymocyte development using a CBAP knockout mouse. CBAP-deficient mice showed normal early thymocyte development and positive selection. In contrast, several negative selection models (including TCR transgene, superantigen staphylococcal enterotoxin B, and anti-CD3 antibody treatment) revealed an attenuation of TCR-induced thymocyte deletion in CBAP knockout mice. This phenotype correlated with a reduced accumulation of BIM upon TCR crosslinking in CBAP-deficient thymocytes. Loss of CBAP led to reduced TCR-induced phosphorylation of proteins involved in both proximal and distal signaling events, including ZAP70, LAT, PLCγ1, and JNK1/2. Moreover, TCR-induced association of LAT signalosome components was reduced in CBAP-deficient thymocytes. Our data demonstrate that CBAP is a novel component in the TCR signaling pathway and modulates thymocyte apoptosis during negative selection.

Exploration of the mechanism of pattern-specific treatments in coronary heart disease with network pharmacology approach

Traditional Chinese medicine (TCM) pattern is a valuable classification method in the treatment of complex disease such as coronary heart disease (CHD). In accordance to TCM patterns, our ancestors created many pertinent TCM formulae, which have been used in China for thousands of years and are still playing an important role in China today. However, the biological mechanism of TCM pattern-specific formulae remains elusive. In this paper, we chose CHD patterns (Qi-stagnation induced blood-stasis syndrome, abbreviated as QSB; Qi-deficiency induced blood-stasis syndrome, abbreviated as QDB) as examples to illustrate the mechanism of their pattern-specific formulae. Using entity grammar systems (EGS) formalism, we built two pharmacologic networks of the formulae and obtained the intersection and difference networks by network comparison. Then we analyzed their common and different mechanisms for treating CHD by GO enrichment analysis. The results indicate that QDB-specific formula takes more special molecular paths to treat CHD, which contribute to more severe pathological changes in comparison with QSB. In this paper, we achieved a better understanding of the pharmacological characteristics of CHD patterns-specific formulae, which is beneficial to explore different therapies for a disease to enhance the effectiveness and pertinence of treatment.

Combined immunodeficiencies with nonfunctional T lymphocytes

Immunodeficiencies with nonfunctional T cells comprise a heterogeneous group of conditions characterized by altered function of T lymphocytes in spite of largely preserved T cell development. Some of these forms are due to hypomorphic mutations in genes causing severe combined immunodeficiency. More recently, advances in human genome sequencing have facilitated the identification of novel genetic defects that do not affect T cell development, but alter T cell function and homeostasis. Along with increased susceptibility to infections, these conditions are characterized by autoimmunity and higher risk of malignancies. The study of these diseases, and of corresponding animal models, has provided fundamental insights on the mechanisms that govern immune homeostasis.