Hodgkin’s lymphoma cells exhibit high expression levels of the PICOT protein
The Shraga Segal Department of Microbiology and Immunology, Faculty of Health Sciences and the Cancer Research Center, Ben Gurion University of the Negev, Beer Sheva, Israel. Journal of Immunotoxicology
(Impact Factor: 2.05).
03/2010; 7(1):8-14. DOI: 10.3109/15476910903427654
PICOT was originally discovered as a protein kinase C (PKC) binding protein in human Jurkat T-lymphocytes in which it was found to modulate PKCtheta-dependent functions. In addition, RT-PCR analysis suggested the expression of PICOT in a wide range of organs and cell types, including cells that are devoid of PKCtheta. We aimed at analyzing the expression of the PICOT protein in mouse lymphoid organs, and to compare them with those of Jurkat T-lymphocytes and other cell lines. We also analyzed whether PICOT expression in T-lymphocytes is dependent on the presence of PKCtheta, and whether it correlates with cell growth rate. Western blot analyses demonstrated PICOT expression in all lymphoid organs and cell lines tested. In addition, similar expression levels were observed in lymphoid organs of wild-type and PKCtheta-null mice, suggesting that PICOT expression in T-lymphocytes is independent of PKCtheta. However, PICOT expression levels were higher in Jurkat T-lymphocytes and other lymphoma cell lines compared to freshly isolated lymphocytes, while T-lymphocyte mitogens, such as concanavalin A, increased PICOT expression concomitantly with the induction of a faster T-lymphocyte growth rate. Finally, immunohistochemistry of freshly-isolated lymph nodes from Hodgkin's lymphoma patients revealed significantly higher levels of PICOT in Hodgkin's cells, compared to the normal surrounding lymphocytes. The present results show a direct correlation between PICOT expression levels and increased cell growth, both in vitro and in vivo, and suggest that immunostaining of PICOT might be useful for in situ identification of transformed cells, such as those of Hodgkin's lymphoma.
Available from: Noah Isakov
- "These results, and the observation that PICOT expression increases in Hodgkin's lymphoma/Reed Sternberg cells (Ohayon et al. 2010), suggest that PICOT has a positive role in supporting/promoting tumor cell growth and/or survival. Previous studies have shown that normal mouse lymphocytes responded to T cell mitogens by an increase in cell proliferation and a simultaneous increase in PICOT expression (Ohayon et al. 2010 "
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ABSTRACT: The protein kinase C-interacting cousin of thioredoxin (PICOT; also termed glutaredoxin 3) protein was discovered a decade ago as a protein kinase C theta (PKCtheta)-binding protein in human T lymphocytes. PICOT possesses an amino-terminal monothiol thioredoxin-like domain and a carboxy-terminal tandem repeat of a monothiol glutaredoxin-like domain. Nevertheless, the enzymatic activities of PICOT and its potential substrates have not yet been characterized and its biological importance is unknown. Earlier studies reported the presence of PICOT in several different cell lines and tissues, but its expression pattern has not been thoroughly investigated. We performed Northern blot analysis of 19 different human organs and tissues and found the expression of PICOT mRNA in all organs and tissues tested. Western blot analysis confirmed the expression of PICOT at the protein level in all organs and tissues tested and showed, in addition, that PICOT and PKCtheta expression in different tissues only partially overlap. These findings support the involvement of PICOT in biological functions that are independent of PKCtheta. To analyze the in vivo expression pattern of PICOT within cells of different human organs, we performed immunohistochemical staining using PICOT-specific antibodies. Analysis of breast, pituitary, adrenal, pancreas, and kidney sections demonstrated a differential expression of PICOT in various cell types, with a predominant cytosolic staining of epithelial cells and low or undetectable levels of PICOT in the stroma.
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ABSTRACT: Anamorsin (AM) (also called CIAPIN-1) is a cell-death-defying factor. AM deficient mice die during late gestation; AM deficient embryos are anemic and very small compared to wild type (WT) embryos. It is thought that AM plays crucial roles in hematopoiesis and embryogenesis. To clarify the mechanisms of AM functions, we performed the yeast-two-hybrid assay to identify AM-interacting molecules; we found that PICOT (PKCθ interacting cousin of thioredoxin) preferentially bound to AM. We also showed that the N-terminal regions of both AM and PICOT were essential for their bindings and the inhibition of interaction of both molecules might lead to the cell growth retardation. Both PICOT and the yeast homolog of AM are known to be iron-sulfur proteins. The phenotype of PICOT deficient mice is very similar to that of anamorsin deficient mice; both mice are embryonic lethal. These data suggest that AM and PICOT might play cooperatively essential roles in embryogenesis as iron-sulfur cluster proteins.
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