• Molecules and Cells
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• v.19 no.1
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• pp.39-45
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• 2005

RPK118 is a sphingosine kinase-1-binding protein that has been implicated in sphingosine 1 phosphate-mediated signaling. It contains a PX (phox homology) domain and two pseudo-kinase domains, and co-localizes with sphingosine kinase-1 on early endosomes. In this study we identified a novel RPK118-binding protein, PRDX3 (peroxiredoxin-3), by yeast two-hybrid screening. The interaction between these proteins was confirmed by pull-down assays and co-immunoprecipitation experiments. Deletion studies showed that RPK118 interacted with PRDX3 through its pseudokinase domains, and with early endosomes through its PX domain. Double immunofluorescence experiments demonstrated that PRDX3 co-localized with RPK118 on early endosomes in COS7 cells. PRDX3 is a member of the antioxidant family of proteins synthesized in the cytoplasm and functioning in mitochondria. Our findings indicate that RPK118 is a PRDX3-binding protein that may be involved in transporting PRDX3 from the cytoplasm to its mitochondrial site of function or to other membrane structures via endosome trafficking.

• BMB Reports
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• v.40 no.5
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• pp.749-756
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• 2007

Phosphorylation on serine/threonine or tyrosine residues of target proteins is an essential and significant regulatory mechanism in signal transduction during many cellular and life processes, including spermatogenesis, oogenesis and fertilization. In the present work, we reported the isolation and characterization of mouse testis-specific serine/threonine kinase 5 (Tssk5), which contains four alternatively spliced variants including, Tssk5$\alpha$, Tssk5$\beta$, Tssk5$\gamma$ and Tssk5$\delta$. Moreover, the locus of Tssk5 is on chromosome 14qC3 and the four variants had a similar high expression in the testis and the heart; however, had a low expression in other tissues, except for Tssk5$\alpha$ which also had comparably high expression in the spleen. Each variant of Tssk5 expression began in the testis 16 days after birth. Aside from TSSK5$\alpha$, the other isoforms have an insertion of ten amino acid residues (RLTPSLSAAG) in region VIb (HRD domain) (His-Arg-Asp). Moreover, only TSSK5$\alpha$ exhibited kinase activity and consistently, a further Luciferase Reporter Assay demonstrated that TSSK5$\beta$, TSSK5$\gamma$ and TSSK5$\delta$ cannot be stimulated at the CREB/CRE responsive pathway in comparison to TSSK5$\alpha$. These findings suggest that TSSK5$\beta$, TSSK5$\gamma$, TSSK5$\delta$ may be pseudokinases due to the insertion, which may damage the structure responsible for active kinase activity. Pull-down assay experiments indicated that TSSK5$\beta$, TSSK5 $\gamma$ and TSSK5$\delta$ can directly interact with TSSK5$\alpha$. In summary, these four isoforms with similar expression patterns may be involved in spermatogenesis through a coordinative way in testis.

• Journal of Life Science
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• v.29 no.6
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• pp.645-652
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• 2019

Non-small cell lung cancer (NSCLC) has the infamous distinction of being the leading cause of global cancer-related death over the past decade, and novel molecular targets are urgently required to change this status. We previously conducted a microarray analysis to investigate the association of transcription factor activating enhancer-binding protein 2C (TFAP2C) with NSCLC and revealed its oncogenic roles in NSCLC development. In this study, to identify new biomarkers for NSCLC, we focused on several oncogenes from the microarray analysis that are transcriptionally regulated by TFAP2C. Here, the cell division cycle 20 (CDC20) and tribbles pseudokinase 3 (TRIB3) were subsequently found as potential potent oncogenes as they are positively regulated by TFAP2C. The results showed that the mRNA and protein levels of CDC20 and TRIB3 were down-regulated in two NSCLC cell lines (NCI-H292 and NCI-H838), which were treated with TFAP2C siRNA, and that the overexpression of either CDC20 or TRIB3 was responsible for promoting cell viability in both NSCLC cell lines. In addition, apoptotic levels of NCI-H292 and NCI-H838 cells treated with TFAP2C siRNA were found to be suppressed by the overexpression of either CDC20 or TRIB3. Together, these results suggest that CDC20 and TRIB3 are positively related to NSCLC tumorigenesis and that they should be considered as potential prognostic markers for developing an NSCLC therapy.