Yanquan Zhang

p15RS Attenuates Wnt/β-Catenin Signaling by Disrupting β-Catenin·TCF4 Interaction

The formation of a β-catenin·TCF4 complex in the nucleus of cells is well known as a prerequisite for the transcription of Wnt target genes. Although many co-factors have been identified to regulate the activity of the β-catenin·TCF4 complex, it remains unclear how the complex association is negatively regulated. In this study, we report that p15RS, a negative regulator of the cell cycle, blocks β-catenin·TCF4 complex formation and inhibits Wnt signaling. We observed that p15RS interacts with β-catenin and TCF4. Interestingly, whereas the interaction of p15RS with β-catenin is increased, its interaction with TCF4 is decreased upon Wnt1 stimulation. Moreover, overexpression of p15RS reduces the interaction of β-catenin with TCF4, whereas the depletion of p15RS enhances their interaction. We further demonstrate that overexpression of p15RS suppresses canonical Wnt signaling and results in retarded cell growth, whereas depletion of p15RS shows an enhanced effect on Wnt signaling. We analyzed that inhibition of Wnt signaling by p15RS leads to decreased expression of CYCLIN D1 and c-MYC, two Wnt targeted genes critical for cell growth. Our data suggest that p15RS inhibits Wnt signaling by interrupting β-catenin·TCF4 complex formation and that Wnt signaling initiates downstream gene expression by removing p15RS from promoters.

GABARAPL1 negatively regulates Wnt/β-catenin signaling by mediating Dvl2 degradation through the autophagy pathway.

Wnt signaling is critical for many biological processes and is tightly regulated. In this study, we found that GABARAPL1 (GABAA receptor-associated protein like 1, GABARAPL1) interacts with Dvl2 by both yeast two-hybrid screening and immunoprecipitation experiments. Furthermore, we observed that p62 is required for the interaction of Dvl2 and GABARAPL1. Luciferase assays indicated that GABARAPL1 represses Wnt/β-catenin signaling stimulated by Wnt1, Dvl2 and β-catenin. We further demonstrated that GABARAPL1 mediates degradation of Dvl2 and the effect is blocked by addition of 3-MA, a specific inhibitor of autophagy. Finally, we provided evidence that over-expression of GABARAPL1 inhibits proliferation and tumor growth of MCF7 cells in vitro and in nude mice. Taken together, our results suggested that GABARAPL1 as a tumor repressor inhibits Wnt signaling via mediating Dvl2 degradation through the autophagy pathway.

Rab21 attenuates EGF-mediated MAPK signaling through enhancing EGFR internalization and degradation.

Epidermal growth factor (EGF) receptor (EGFR) signal transduction is regulated by endocytosis where many Rab proteins play an important role in the determination of the receptor recycle or degradation. In an effort to better understand how EGF signaling is regulated, we examined the role of Rab21 in regulation of the degradation and signal transduction of the EGFR. Using a transient expression protocol in HEK293T and HeLa cells, we found that Rab21 enhanced the degradation of EGFR through accelerating its internalization in both EGF-independent and EGF-dependent manners. We further demonstrated that Rab21 interacted with EGFR by immunoprecipitation experiments. Interestingly, we observed that overexpression of Rab21 attenuated EGF-mediated mitogen-activated protein kinase (MAPK) signaling by inducing EGFR degradation. Taken together, these data suggest that Rab21 plays a negative role in the EGF-mediated MAPK signaling pathway.

Solving processes for a system of first-order fuzzy differential equations

Abstract In this third paper of a series of reports on fuzzy differential equations, we consider the system of first-order, inhomogeneous fuzzy differential equations d d t X (t) + A (t) X (t) = F (t) (1) with X (0) = X 0 , where d X (t)/t is an n-dimensional vector of first same-order (or reverse-order) derived functions of an n-dimensional vector, X (t) = ( X 1 (t),…, X n (t)) T , of unknown fuzzy set-valued functions, that is, d dt X (t) = d dt X 1 (t),…, d dt X n (t) T ; F (t) , is an n-dimensional vector, ( F 1 (t),… F n (t)) T of known fuzzy set-valued functions; A(t) is an n × n matrix of known real functions. We introduce the time domain and frequency domain methods for the solutions of the system of first-order fuzzy differential equations (1). The solving processes of time domain and frequency domain for the system of first-order fuzzy differential equations with constant coefficients and variable coefficients are put forward. One example is considered in order to demonstrate the rationality and validity of the methods. The work provides an indispensable mathematical tool for setting up the theories of fuzzy stochastic differential equations [7], fuzzy dynamical systems [3], fuzzy random vibration [8], fuzzy stochastic dynamical systems [10, 11, 14–16] and fuzzy stochastic systems [17–19].

SIPAR negatively regulates STAT3 signaling and inhibits progression of melanoma.

Persistently activated STAT3 is important for tumorigenesis in a variety of cancers, including melanoma. Although many co-factors in the regulation of STAT3 activity have been identified, it remains unclear how STAT3 phosphorylation is negatively regulated. Here, we report that SIPAR (STAT3-Interacting Protein As a Repressor) inhibits STAT3 activity by accelerating its dephosphorylation. We observed that SIPAR directly interacted with STAT3 upon IL-6 stimulation. Moreover, over-expression of SIPAR reduced, whereas depletion enhanced, the level of phosphorylated STAT3. We further demonstrated that SIPAR inhibited the growth of melanoma cells by decreasing the level of phosphorylated STAT3 and the expression of its target genes. These results suggest that SIPAR, functioning as a new negative regulator, inhibits STAT3 activity by enhancing its dephosphorylation and represses melanoma progression.

Characterization of a monoclonal antibody against CREPT, a novel protein highly expressed in tumors.

CREPT (cell-cycle related and expression-elevated protein in tumor), a novel gene also called RPRD1B and C20ORF77, was recently identified to promote tumorigenesis through up-regulation of the expression of genes related to cell cycle. The previous study demonstrated that CREPT is highly expressed in a variety of tumors and enhances the expression of Cyclin D1 by promoting the formation of a chromatin loop. To study the correlation of CREPT expression with clinical factors in different tumors, we generated a monoclonal antibody (3E10) using purified recombinant human GST-CREPT protein as an antigen. In this study, we characterized the specificity of the monoclonal antibody and cloned the gene encoding the antibody for preparation of industrial production. Our results showed that the monoclonal antibody 3E10 was sensitive and specific to recognize human endogenous CREPT protein. We have mapped the epitope of the antibody and cloned the variable region sequence of the gene encoding the antibody. We confirmed that the cloned gene produced an equivalent antibody as that produced by the original hybridoma. This study provided a basis for large-scale production of the CREPT antibody, which will be useful for the study of the role of CREPT in different tumors.

Carboxyl terminus of Hsp70-interacting protein regulation of osteoclast formation in mice through promotion of tumor necrosis factor receptor-associated factor 6 protein degradation.

Carboxyl terminus of Hsp70‐interacting protein (CHIP or STUB1) is an E3 ligase that regulates the stability of several proteins involved in tumor growth and metastasis. However, the role of CHIP in bone growth and bone remodeling in vivo has not been reported. This study was undertaken to investigate the role and mechanism of CHIP in regulation of bone mass and bone remodeling.

THE THEORY OF RESPONSE ANALYSIS OF FUZZY STOCHASTIC DYNAMICAL SYSTEMS WITH A SINGLE DEGREE OF FREEDOM

Most real-life structural/mechanical systems have complex geometrical and material properties and operate under complex fuzzy environmental conditions. These systems are certainly subjected to fuzzy random excitations induced by the environment. For an analytical treatment of such a system subjected to fuzzy random excitations, it becomes necessary to establish the general theory of dynamic response of a system to fuzzy random excitations. In this paper, the theory of response, fuzzy mean response and fuzzy covariance response of a single-degree-of-freedom (sdf) system to fuzzy random excitations in the time domain and frequency domain is put forward. The theory of response analysis of an sdf system to both stationary and non-stationary fuzzy random excitations in the time domain and frequency domain is established. Two examples are considered in order to demonstrate the rationality and validity of the theory, and the models of stationary filtered white noise and non-stationary filtered white noise fuzzy stochastic processes of the earthquake ground motion are set up. Methods of analysis for fuzzy random seismic response of sdf systems are put forward using the principles of response analysis of an sdf fuzzy random dynamic system.

CREPT facilitates colorectal cancer growth through inducing Wnt/β-catenin pathway by enhancing p300-mediated β-catenin acetylation

Using whole genome sequencing, we identified gene amplification of CREPT in colorectal cancer (CRC). In this study, we aim to clarify its clinical significance, biological effects, and mechanism in CRC. CREPT was upregulated in CRC cell lines and in 47.37% (72/152) of primary CRC tumors. Amplification of CREPT was detected in 48.28% (56/116) of primary CRC tumors, which was positively correlated with its overexpression (P < 0.001). Multivariate analysis showed that CRC patients with CREPT protein overexpression were significantly associated with poor disease-free survival (P < 0.05). CREPT significantly accelerated CRC cell proliferation and metastasis both in vitro and in vivo. RNA-sequencing (seq) analysis uncovered that the tumor-promoting effect by CREPT was attributed to enhancing Wnt/β-catenin signaling. Using co-immunoprecipitation coupled with mass spectroscopy, we identified p300 protein was a novel CREPT interacting partner. CREPT greatly increased the interaction between p300 and β-catenin, thus promoting p300-mediated β-catenin acetylation and stabilization. Moreover, CREPT cooperated with p300, leading to elevated active histone acetylation markers H3K27ac and H4Ac and decreased repressive histone marker H3K9me3 at the promoters of Wnt downstream targets. In summary, CREPT plays a pivotal oncogenic role in colorectal carcinogenesis through promoting Wnt/β-catenin pathway via cooperating with p300. CREPT may serve as a prognostic biomarker of patients with CRC.

Dishevelled-DEP domain interacting protein (DDIP) inhibits Wnt signaling by promoting TCF4 degradation and disrupting the TCF4/β-catenin complex

The TCF4/beta-catenin complex, the executor of canonical Wnt/beta-catenin signaling, is regulated by a variety of factors. Among these, Dishevelled (Dvl) is a critical regulator that releases beta-catenin from degradation and stabilizes TCF4/beta-catenin complex. Here, we report that DDIP (Dishevelled-DEP domain Interacting Protein, also named as Spats1, spermatogenesis associated, serine-rich 1), a novel protein that interacts with Dvl, regulates Wnt signaling. We provide evidence that DDIP suppresses Lef-1 luciferase reporter activity stimulated by Wnt1, Dvl2 or beta-catenin, interacts with the TCF4/beta-catenin complex, and disrupts the interaction of TCF4 and beta-catenin by promoting TCF4 degradation through the proteasome pathway. Our results indicate that DDIP is a negative regulator of the canonical Wnt signaling.