Protein tyrosine phosphatases are often exploited and subverted by pathogenic bacteria to cause human diseases. The tyrosine phosphatase mPTPB from Mycobacterium tuberculosis is an essential virulence factor that is secreted by the bacterium into the cytoplasm of macrophages, where it mediates mycobacterial survival in the host. Consequently, there is considerable interest in understanding the mechanism by which mPTPB evades the host immune responses, and in developing potent and selective mPTPB inhibitors as unique antituberculosis (antiTB) agents. We uncovered that mPTPB subverts the innate immune responses by blocking the ERK1/2 and p38 mediated IL-6 production and promoting host cell survival by activating the Akt pathway. We identified a potent and selective mPTPB inhibitor I-A09 with highly efficacious cellular activity, from a combinatorial library of bidentate benzofuran salicylic acid derivatives assembled by click chemistry. We demonstrated that inhibition of mPTPB with I-A09 in macrophages reverses the altered host immune responses induced by the bacterial phosphatase and prevents TB growth in host cells. The results provide the necessary proof-of-principle data to support the notion that specific inhibitors of the mPTPB may serve as effective antiTB therapeutics.combinatorial chemistry | pathogen-host interaction | phosphatase inhibitor | signaling mechanism
The With-No-Lysine (K) (WNK) kinases play a critical role in blood pressure regulation and body fluid and electrolyte homeostasis. Herein, we introduce the first orally bioavailable pan-WNK-kinase inhibitor, WNK463, that exploits unique structural features of the WNK kinases for both affinity and kinase selectivity. In rodent models of hypertension, WNK463 affects blood pressure and body fluid and electro-lyte homeostasis, consistent with WNK-kinase-associated physiology and pathophysiology.
The phosphatase of regenerating liver (PRL) phosphatases are implicated in a number of tumorigenesis and metastasis processes. The PRLs are unique among protein-tyrosine phosphatases in that they have extremely low phosphatase activity, a high propensity for trimer formation, and a polybasic region that precedes the C-terminal prenylation motif. To investigate the functional significance of these distinctive biochemical and structural features, we established a cell-based system in which ectopic PRL1 expression increased cell proliferation and migration, whereas knockdown of endogenous PRL1 abrogated these cellular activities. We showed that the intrinsic PRL1 phosphatase activity is obligatory for its biological function. We provided evidence that trimerization may be a general property for all PRL enzymes, and that PRL1 trimer formation is essential for the PRL1-mediated cell growth and migration. This finding indicates a novel mechanism for phosphatase regulation. We further demonstrated that the conserved C-terminal polybasic region is important for specific phosphoinositide recognition by PRL1. Both the polybasic residues and the adjacent prenylation motif are required for proper PRL1 subcellular localization and full biological activity.
The PRL (phosphatase of regenerating liver) phosphatases represent a distinct class of protein tyrosine phosphatases, which are implicated in tumorigenesis and metastasis processes. Accumulating evidence indicates that alteration in PRL1 expression affects cell motility and tumor metastasis, although the biochemical pathways regulated by PRL1 remain less well defined. We find that elevated expression of PRL1 increases the levels of the matrix metalloproteinases MMP2 and MMP9. We have studied whether MMP2 and MMP9 are regulated by PRL1 and participate in PRL1-dependent cell migration and invasion. To this end, knockdown or inhibition of MMP2 and MMP9 by either siRNA or a specific small molecule inhibitor blocks the PRL1-mediated cell migration and invasion. In addition, we report that up-regulation of PRL1 activates the Src kinase through increased Tyr416 phosphorylation, which culminates in the phosphorylation of the focal adhesion proteins FAK and p130 Cas , as well as ERK1/2 activation. We provide evidence that both the Src and ERK1/2 pathways contribute to the increased motility of the PRL1 cells. We further demonstrate that Src and ERK1/2 activities are required for the PRL1-induced increase in MMP2 and MMP9, likely through activation of the transcription factors AP1 and Sp1. Accordingly, increased PRL1 expression results in activation of Src and ERK1/2, which stimulates MMP2 and MMP9 production, leading to increased cell migration and invasion.Protein tyrosine phosphorylation plays an important role in regulating a wide array of signaling events essential for the proper function of many cellular processes, including proliferation, metabolism, differentiation, survival/apoptosis, as well as adhesion and motility (1). The level of tyrosine phosphorylation is modulated by the coordinated action of protein tyrosine kinases and phosphatases. Similar to the kinases, dysregulation of protein tyrosine phosphatases has been linked to several human diseases such as diabetes, autoimmune disorders and cancer (2). The PRL (phosphatase of regenerating liver) phosphatases represent a distinct class of protein tyrosine phosphatases, which are implicated in a number of tumorigenesis and metastasis processes (3). The PRL phosphatases include three members (PRL1, PRL2, and PRL3), which share a high degree (>75%) of amino acid sequence identity. PRL1 was originally identified as an immediate early gene in regenerating liver (4). Subsequent studies revealed that PRL1 expression is elevated in several tumor cell lines, and cells expressing high levels of PRL1 exhibit enhanced proliferation and anchorage-independent growth (4-6). Interestingly, up-regulation of the related PRL2 and PRL3 also promotes cell growth (3). In addition to a role in cell proliferation, the PRLs are also involved in tumor metastasis. For example, the PRL3 message is amplified in colorectal cancer metastases,
Isocitrate dehydrogenase (IDH) is a key rate-limiting enzyme in the Krebs cycle that plays an important role in energy metabolism. In recent years, it has been found that IDH mutations are closely related to the occurrence and development of glioma, and it is a notable potential therapeutic target. First, IDH mutations can produce high levels of 2-hydroxyglutaric acid (2-HG), thereby inhibiting glioma stem cell differentiation. At the same time, IDH mutations can upregulate vascular endothelial growth factor (VEGF) to promote the formation of the tumor microenvironment. In addition, IDH mutations can also induce high levels of hypoxia-inducible factor-1α (HIF-1α) to promote glioma invasion. Ultimately, these changes will lead to the development of glioma. Currently, a large number of IDH inhibitors and vaccines have entered clinical trials, representing progress in the treatment of glioma patients.
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