Regulation of Vaccinia H1-related (VHR) Phosphatase Activity by NSC-87877

Abstract

Half maximal inhibitory constant of enzyme was determined to 7.83 ± 0.98 µM. VHR phosphatase (100 nM) was incubated with various concentrations of NSC-87877 at 37 o C for 30 min. Fluorescence emission from the product was measured with a multiwell plate reader as described in Experimental section.Based on amino-acid sequences of catalytic domains, protein tyrosine phosphatases (PTPs) can be classified into four groups 1 ; class I Cys-based PTPs, class II Cys-based PTPs, class III Cys-based PTPs, and Asp-based PTPs. Each PTP has a characteristic role in a variety of cellular processes including cellular metabolism, growth, proliferation, differentiation and also has been emerged as a therapeutic target in many diseases such as diabetes, leukemia, neurodegradation, and cancer. Class I PTPs comprise dual specificity phosphatases (DUSPs) including VHR that has diverse substrate specificities both or either on phospho-Tyr, phospho-Ser, and phospho-Thr residues. Class II PTPs that dephosphorylate only pTyr are encoded by a single gene ACP1 and related to diseases like Alzheimer's disease and asthma. Class III PTPs comprise CDC25 family proteins that regulate cell cycle by acting on Cdks. They dephosphorylate Thr-Tyr motifs of N-terminal Cdks, thus keep them from driving the cell progression.2 Asp-based PTPs encoded by only four Eya genes recently have been listed as a new family.VHR phosphatase, also called DUSP3, is a 20 kDa protein that might be one of the smallest known PTPs. VHR phosphatase can be elucidated by two particular characteristics in cellular physiology. First, VHR phosphatase shows more expression in the nucleus of cancer cells than that of normal cells. It is not due to the increase of transcription of VHR gene, but due to stabilization VHR phosphatase in cancer cell. Its expression was increased in cervix carcinoma and prostate cancer. 4 Another intriguing aspect of VHR phosphatase is that it fluctuates during the phases of cell cycle. VHR phosphatase during G1 phase is not detected due to rapid degradation. Gradually, it accumulates by means of its augmented transcription during late G1 and S phases. 5 The siRNA interference analyses also show that depletion of VHR phosphatase arrests cells at the G 1 /S, and G 2 /M phases. 5 Highly active extracellular signal regulated kinase (ERK) is a main reason of the cell cycle arrest. 6 Elevated VHR phosphatase expression results in cell cycle progression by dephosphorylating ERK. Due to its elevated protein level in cancers such as cervix carcinoma and prostate cancer and involvement in cell cycle progression, VHR phosphatase has been emerged as a therapeutic target. Therefore, it is important to identify novel inhibitor of VHR phosphatase for cancer treatment. Several VHR phosphatase inhibitors including stevastelins, 7 glucosamine-aminoehoxy triphenyltin (GATPT), 8 RK-682, 9 and 4-iA 10 have been identified so far. In search for more putative VHR phosphatase inhibitors, we investigated whether 8-hydroxy-7-[(6-sulfo-2-naphthyl)azo]-5-quinolinesulfonic acid ...

Inhibition of SHP-2 Activity by PRL-3 Inhibitor I

“…[25][26][27][28][29] In this study, we confirmed that PRL-3 inhibitor I which regulates SHP-2 function could be a promising target for drug development.…”

NSC-87877 Inhibits Cell Growth by Suppressing ERK Signaling

“…12,13 Using in vitro phosphatase assays, we have previously found that DUSP3, DUSP14, DUSP23, DUSP26, ACP1, Cdc25A and Cdc25B are inhibited by NSC-87877. [14][15][16][17][18][19] PTPs that are inhibited by NSC-87877 and their specificity for MAPKs were listed in Table 1. Since those NSC-87877 targets are involved in either cell growth or apoptosis, it is of interest to investigate whether cells survive or die when cells are treated with NSC-87877.…”