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Yunpeng Bai,
Yong Luo,
Sijiu Liu,
Lujuan Zhang,
Kui Shen,
Yuanshu Dong, Chad D Walls,
Lawrence A Quilliam,
Clark D Wells,
Youjia Cao,
Zhong-Yin Zhang
[show abstract]
[hide abstract]
ABSTRACT: Phosphatases of the regenerating liver (PRL) play oncogenic roles in cancer development and metastasis. Although previous studies indicate that PRL-1 promotes cell growth and migration by activating both the ERK1/2 and RhoA pathways, the mechanism by which it activates these signaling events remains unclear. We have identified a PRL-1-binding peptide (Peptide 1) that shares high sequence identity with a conserved motif in the Src homology 3 (SH3) domain of p115 Rho GTPase-activating protein (GAP). p115 RhoGAP directly binds PRL-1 in vitro and in cells via its SH3 domain. Structural analyses of the PRL-1·Peptide 1 complex revealed a novel protein-protein interaction whereby a sequence motif within the PxxP ligand-binding site of the p115 RhoGAP SH3 domain occupies a folded groove within PRL-1. This prevents the canonical interaction between the SH3 domain of p115 RhoGAP and MEKK1 and results in activation of ERK1/2. Furthermore, PRL-1 binding activates RhoA signaling by inhibiting the catalytic activity of p115 RhoGAP. The results demonstrate that PRL-1 binding to p115 RhoGAP provides a coordinated mechanism underlying ERK1/2 and RhoA activation.
Journal of Biological Chemistry 12/2011; 286(49):42316-24. · 4.77 Impact Factor
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Yunpeng Bai,
Yong Luo,
Sijiu Liu,
Lujuan Zhang,
Kui Shen,
Yuanshu Dong, Chad D. Walls,
Lawrence A. Quilliam,
Clark D. Wells,
Youjia Cao,
Zhong-Yin Zhang
[show abstract]
[hide abstract]
ABSTRACT: Phosphatases of the Regenerating Liver (PRL) play oncogenic roles in cancer development and metastasis. While previous studies
indicate that PRL-1 promotes cell growth and migration by activating both the ERK1/2 and RhoA pathways, the mechanism by which
it activates these signaling events remains unclear. We have identified a PRL-1 binding peptide (Peptide 1) that shares high
sequence identity to a conserved motif in the SH3 domain of p115 RhoGAP. p115 RhoGAP is found to directly bind PRL-1 in vitro
and in cells via its SH3 domain. Structural analyses of the PRL-1/Peptide 1 complex reveals a novel protein-protein interaction
whereby a sequence motif within the PxxP ligand binding site of the p115 RhoGAP SH3 domain occupies a folded groove within
PRL-1. This prevents the canonical interaction between the SH3 domain of p115 RhoGAP and MEKK1 and results in activation of
ERK1/2. Further, PRL-1 binding activates RhoA signaling by inhibiting the catalytic activity of p115 RhoGAP. The results demonstrate
that PRL-1 binding to p115 RhoGAP provides a coordinated mechanism underlying ERK1/2 and RhoA activation.
Journal of Biological Chemistry 10/2011; · 4.77 Impact Factor
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[show abstract]
[hide abstract]
ABSTRACT: Phosphatase of regenerating liver 3 (PRL3) is up-regulated in cancer metastases. However, little is known of PRL3-mediated cellular signaling pathways. We previously reported that elevated PRL3 expression increases Src kinase activity, which likely contributes to the increased tumorigenesis and metastasis potential of PRL3. PRL3-induced Src activation is proposed to be indirect through down-regulation of Csk, a negative regulator of Src. Given the importance of PRL3 in tumor metastasis and the role of Csk in controlling Src activity, we addressed the mechanism by which PRL3 mediates Csk down-regulation. PRL3 is shown to exert a negative effect on Csk protein synthesis, rather than regulation of Csk mRNA levels or protein turnover. Interestingly, the preferential decrease in Csk protein synthesis is a consequence of increased eIF2 phosphorylation resulting from PRL3 expression. Reduced Csk synthesis also occurs in response to cellular stress that induces eIF2 phosphorylation, indicating that this regulatory mechanism may occur in response to a wider spectrum of cellular conditions known to direct translational control. Thus, we have uncovered a previously uncharacterized role for PRL3 in the gene-specific translational control of Csk expression.
Journal of Biological Chemistry 05/2008; 283(16):10339-46. · 4.77 Impact Factor
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Yesim Gökmen-Polar,
Daniel Escuin, Chad D Walls,
Sharon E Soule,
Yuefang Wang,
Kerry L Sanders,
Theresa M Lavallee,
Mu Wang,
Brian D Guenther,
Paraskevi Giannakakou,
George W Sledge
[show abstract]
[hide abstract]
ABSTRACT: 2-Methoxyestradiol is an estradiol metabolite with significant antiproliferative and antiangiogenic activity independent of estrogen receptor status. To identify a molecular basis for acquired 2-methoxyestradiol resistance, we generated a stable 2-methoxyestradiol-resistant (2ME2R) MDA-MB-435 human cancer cell line by stepwise exposure to increasing 2-methoxyestradiol concentrations. 2ME2R cells maintained in the presence of the drug and W435 cells maintained in the absence of the drug showed 32.34- to 40.07-fold resistance to 2-methoxyestradiol. Cross-resistance was observed to Vinca alkaloids, including vincristine, vinorelbine, and vinblastine (4.29- to 6.40-fold), but minimal resistance was seen to colchicine-binding agents including colchicine, colcemid, and AVE8062A (1.72- to 2.86-fold). No resistance was observed to paclitaxel and epothilone B, polymerizing agents (0.89- to 1.14-fold). Genomic sequencing identified two different heterozygous point mutations in the class I (M40) isotype of beta-tubulin at amino acids 197 (Dbeta197N) and 350 (Kbeta350N) in 2ME2R cells. Tandem mass spectrometry confirmed the presence of both wild-type and the mutant beta-tubulin in 2ME2R cells at the protein level. Consistently, treatment of parental P435 cells with 2-methoxyestradiol resulted in a dose-dependent depolymerization of microtubules, whereas 2ME2R cells remained unaffected. In contrast, paclitaxel affected both cell lines. In the absence of 2-methoxyestradiol, 2ME2R cells were characterized by an elevated level of detyrosination. Upon 2-methoxyestradiol treatment, levels of acetylated and detyrosinated tubulins decreased in P435 cells, while remaining constant in 2ME2R cells. These results, together with our structure-based modeling, show a tight correlation between the antitubulin and antiproliferative effects of 2-methoxyestradiol, consistent with acquired tubulin mutations contributing to 2-methoxyestradiol resistance.
Cancer Research 11/2005; 65(20):9406-14. · 7.86 Impact Factor
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Yinong Zhang,
Leslie van der Fits,
Jane S Voerman,
Marie-Jose Melief,
Jon D Laman,
Mu Wang,
Haitao Wang,
Minhui Wang,
Xinna Li, Chad D Walls,
Dipika Gupta,
Roman Dziarski
[show abstract]
[hide abstract]
ABSTRACT: N-acetylmuramoyl-l-alanine amidase (NAMLAA) hydrolyzes bacterial peptidoglycan and is present in human serum. A peptidoglycan-recognition protein 2 (PGLYRP2) is expressed in human liver and has N-acetylmuramoyl-l-alanine amidase activity. Here, we determined the amino acid sequences of human serum NAMLAA and liver PGLYRP2 and tested the hypothesis that serum NAMLAA and PGLYRP2 are the same protein. Liver PGLYRP2 and serum NAMLAA had the same mass determined by mass spectrometry and polyacrylamide gel electrophoresis, and both proteins and recombinant PGLYRP2 reacted with polyclonal anti-NAMLAA and anti-PGLYRP2 antibodies, and with monoclonal anti-NAMLAA antibodies. Digestion of serum NAMLAA with trypsin, chymotrypsin, or trypsin plus V8 protease, or with CNBr yielded, respectively, 37, 40, and 3 overlapping peptides that matched 100% and covered 81% of the deduced amino acid sequence of mature PGLYRP2. These peptides overlapped all exon-intron junctions indicating no alternative splice forms. Digestion of liver PGLYRP2 with trypsin yielded 23 peptides that matched 100% and covered 44% of the deduced amino acid sequence of mature PGLYRP2. Serum NAMLAA had a C398-C404 disulfide, partial phosphorylation of S218, and deamidation of N253 and N301. These results indicate that serum NAMLAA and liver PGLYRP2 are the same protein encoded by the pglyrp2 gene.
Biochimica et Biophysica Acta 09/2005; 1752(1):34-46. · 4.66 Impact Factor
