• Molecules and Cells
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• 제42권8호
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• pp.604-616
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• 2019

Phosphoserine phosphatase (PSPH) is one of the key enzymes of the L-serine synthesis pathway. PSPH is reported to affect the progression and survival of several cancers in an L-serine synthesis-independent manner, but the mechanism remains elusive. We demonstrate that PSPH promotes lung cancer progression through a noncanonical L-serine-independent pathway. PSPH was significantly associated with the prognosis of lung cancer patients and regulated the invasion and colony formation of lung cancer cells. Interestingly, L-serine had no effect on the altered invasion and colony formation by PSPH. Upon measuring the phosphatase activity of PSPH on a serine-phosphorylated peptide, we found that PSPH dephosphorylated phospho-serine in peptide sequences. To identify the target proteins of PSPH, we analyzed the protein phosphorylation profile and the PSPH-interacting protein profile using proteomic analyses and found one putative target protein, IRS-1. Immunoprecipitation and immunoblot assays validated a specific interaction between PSPH and IRS-1 and the dephosphorylation of phospho-IRS-1 by PSPH in lung cancer cells. We suggest that the specific interaction and dephosphorylation activity of PSPH have novel therapeutic potential for lung cancer treatment, while the metabolic activity of PSPH, as a therapeutic target, is controversial.

• BMB Reports
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• 제29권5호
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• pp.417-422
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• 1996

In clonal sublines with different metastatic ability derived from Dunning rat prostate tumor, phosphoamino acid levels of cellular proteins were determined. Cell lines with high metastatic ability exhibited 5-fold higher phosphotyrosine level than did cell lines with low metastatic ability, while the contents of phosphoserine and phosphothreonine were similar among cell lines examined, All cell lines showed similar activities of protein tyrosine kinases as well as overall protein kinases. Phosphotyrosine protein phosphatase (PTPP) activities of the cells with high metastatic ability were very low, compared to those of the cells with low metastatic ability, suggesting that the different phosphotyrosine levels among the cell lines were due to the difference in PTPP activities rather than protein tyrosine kinase activities. Cellular activities of prostatic acid phosphatase (PAcP), which has been reported to possess phosphotyrosine protein phosphatase activity, were shown to be inversely related to the phosphotyrosine levels and metastatic abilities of the prostate tumor cells, These results suggest that cellular PAcP activity, regulating phosphotyrosine levels of cellular proteins, is closely connected with the metastatic process in prostate tumor cells and can be utilized as a good biochemical marker for the diagnosis of metastasis of prostate tumor.

• 한국미생물생명공학회:학술대회논문집
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• 한국미생물생명공학회 2001년도 Proceedings of 2001 International Symposium
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• pp.135-136
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• 2001

The Tk-ptp gene encoding a protein tyrosine phosphatase (PTPase) from the hyperthermophilic archaeon Thermococcus kodakaraensis KODI was cloned and sequenced. Sequence analysis indicated that Tk-ptp encoded a protein consisting 147 amino acid residues (16,953 Da). The wild type and the mutants were expressed in Escherichia coli cells as His-tagged fusion proteins and examined for enzyme characteristics. Tk-PTP possessed two unique features that were not found in eucaryal and bacterial counterparts. First, the recombinant Tk-PTP showed the phosphatase activity not only for the phosphotyrosine but also phosphoserine. Second, the conserved Asp (Asp-63), which was considered to be a critical residue, was not involved in catalysis. In order to know a specific substrate for Tk-PTP, C93S mutant was used to trap substrate protein. Proteins of 120, 60 and 53 kDa were isolated specifically from KODI cell lysates by affinity chromatography with Tk-PTP-C93S. It is suggested that these proteins are tyrosine-phosphorylated substrates of Tk-PTP.

• Journal of Gastric Cancer
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• 제7권2호
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• pp.59-66
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• 2007

목적: 위암 세포주 및 조직에서 다중 표지자 mRNA 발현을 정량적 RT-PCR 검사를 통해 확인함으로써 이들 표지자를 이용하여 위암의 복강내 미세전이 진단이 가능한가를 평가하고자 본 연구를 시행하였다. 대상 및 방법: 12개의 인체 위암 세포주와 10개의 위암 조직을 대상으로 Carcinoembryonic antigen (CEA), Cytokeratin 20 (CK20), Dopa decarboxylase (DDC), L-3-phosphoserine phosphatase (L3PP)의 네 가지 mRNA를 이용한 정량적 RT-PCR 다중 표지자 분석을 시행하였다. 결과: 12개의 인체 위암 세포주 중 CEA는 4개(33%), CK-20는 1개(8%), DDC는 6개(50%), L3PP는 12개 세포주 모두(100%)에서 과발현되었다. 10개의 위암 조직 중 CEA는 9개, CK20은 3개, DDC는 9개, L3PP는 10개 조직 모두에서 과발현되었다. L3PP는 모든 위암 세포주와 조직에서 과발현을 나타내었으나 과발현 정도는 비교적 낮게 측정된 반면, CEA와 DDC는 일부 위암 세포주 및 조직에서만 과발현을 나타내었지만 파발현 시 충분한 발현도를 나타내었다. 결론: 위암 환자에서 하나 이상의 암 특이적 유전자를 이용한 다중 표지자 분석은 단일 표지자 분석이 가지는 단점을 보완할 수 있을 것으로 예상되며, CEA, DDC, 및 L3PP의 세 가지 mRNA가 후보 유전자로 사용될 수 있을 것으로 생각한다.