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Investigation of POPX2 phosphatase functions by comparative phosphoproteomic analysis
Author(s) -
Singh Pritpal,
Gan Chee Sian,
Guo Tiannan,
Phang HuiQun,
Sze Siu Kwan,
Koh Cheng Gee
Publication year - 2011
Publication title -
proteomics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.26
H-Index - 167
eISSN - 1615-9861
pISSN - 1615-9853
DOI - 10.1002/pmic.201100044
Subject(s) - motility , phosphatase , kinase , biology , phosphorylation , biochemistry , serine , microbiology and biotechnology , signal transduction , gsk 3 , extracellular , threonine , enzyme , cancer cell , cancer , genetics
Identifying the substrates and biochemical pathway regulated by phosphatases has always been more challenging than finding those regulated by kinases. Here, we report the use of phosphoproteomic methods to analyse the pathways regulated by POPX2 (partner of PIX 2) phosphatase. POPX2 is a serine/threonine phosphatase, found in many cancer types. The levels of the POPX2 have been found to be up‐regulated in the more invasive breast cancer cells compared with non‐invasive ones. Our observations also suggest that POPX2 level is positively correlated with cell motility. Thus, finding substrates or pathways regulated by POPX2 will help to elucidate the regulatory mechanism of cancer cell motility and invasiveness. We have also developed and validated a protocol using electrostatic repulsion‐hydrophilic interaction chromatography (ERLIC) to enrich the phosphopeptides followed by LC‐MS/MS to allow comparison between the phosphoproteomes of control and POPX2 overexpressing cells. With this approach, we were able to identify a biochemical pathway through which POPX2 exerts its apparent cellular function: the regulation of activity of glycogen synthase kinase‐3, which in turn modulates extracellular signal‐regulated kinase and cell motility.