Violacein switches off low molecular weight tyrosine phosphatase and rewires mitochondria in colorectal cancer cells.

In the last decade, emerging evidence has shown that low molecular weight protein tyrosine phosphatase (LMWPTP) not only contributes to the progression of cancer but is associated with prostate low survival rate and colorectal cancer metastasis. We report that LMWPTP favors the glycolytic profile in some tumors. Therefore, the focus of the present study was to identify metabolic enzymes that correlate with LMWPTP expression in patient samples. Exploratory data analysis from RNA-seq, proteomics, and histology staining, confirmed the higher expression of LMWPTP in CRC. Our descriptive statistical analyses indicate a positive expression correlation between LMWPTP and energy metabolism enzymes such as acetyl-CoA carboxylase (ACC) and fatty acid synthase (FASN). In addition, we examine the potential of violacein to reprogram energetic metabolism and LMWPTP activity. Violacein treatment induced a shift of glycolytic to oxidative metabolism associated with alteration in mitochondrial efficiency, as indicated by higher oxygen consumption rate. Particularly, violacein treated cells displayed higher proton leak and ATP-linked oxygen consumption rate (OCR) as an indicator of the OXPHOS preference. Notably, violacein is able to bind and inhibit LMWPTP. Since the LMWPTP acts as a hub of signaling pathways that offer tumor cells invasive advantages, such as survival and the ability to migrate, our findings highlight an unexplored potential of violacein in circumventing the metabolic plasticity of tumor cells.

Oncophosphosignaling Favors a Glycolytic Phenotype in Human Drug Resistant Leukemia.

In chemoresistant leukemia cells (Lucena-1), the low molecular weight protein tyrosine phosphatase (LMWPTP) is about 20-fold more active than in their susceptible counterpart (K562). We found this phosphatase ensures the activated statuses of Src and Bcr-Abl. Since, phosphorylation and dephosphorylation of proteins represent a key post-translational regulation of several enzymes, we also explored the kinome. We hereby show that LMWPTP superactivation, together with kinome reprogramming, cooperate towards glucose addiction. Resistant leukemia cells present lower levels of oxidative metabolism, in part due to downexpression of the following mitochondrial proteins: pyruvate dehydrogenase subunit alpha 1, succinate dehydrogenase, and voltage-dependent anion channel. Those cells displayed higher expression levels of glucose transporter 1 and higher production of lactate. In addition, Lucena-1 siRNA LMWPTP cells showed lower expression levels of glucose transporter 1 and lower activity of lactate dehydrogenase. On the other hand, K562 cells overexpressing LMWPTP presented higher expression/activity of both proteins. In this study, we show that LMWPTP is a pivotal mediator of metabolic reprogramming that confers survival advantages to leukemia cells against death stimuli. J. Cell. Biochem. 118: 3846-3854, 2017. © 2017 Wiley Periodicals, Inc.

Crystal structures of the apo form and a complex of human LMW-PTP with a phosphonic acid provide new evidence of a secondary site potentially related to the anchorage of natural substrates.

Low molecular weight protein tyrosine phosphatases (LMW-PTP, EC 3.1.3.48) are a family of single-domain enzymes with molecular weight up to 18 kDa, expressed in different tissues and considered attractive pharmacological targets for cancer chemotherapy. Despite this, few LMW-PTP inhibitors have been described to date, and the structural information on LMW-PTP druggable binding sites is scarce. In this study, a small series of phosphonic acids were designed based on a new crystallographic structure of LMW-PTP complexed with benzylsulfonic acid, determined at 2.1Å. In silico docking was used as a tool to interpret the structural and enzyme kinetics data, as well as to design new analogs. From the synthesized series, two compounds were found to act as competitive inhibitors, with inhibition constants of 0.124 and 0.047 mM. We also report the 2.4Å structure of another complex in which LMW-PTP is bound to benzylphosphonic acid, and a structure of apo LMW-PTP determined at 2.3Å resolution. Although no appreciable conformation changes were observed, in the latter structures, amino acid residues from an expression tag were found bound to a hydrophobic region at the protein surface. This regions is neighbored by positively charged residues, adjacent to the active site pocket, suggesting that this region might be not a mere artefact of crystal contacts but an indication of a possible anchoring region for the natural substrate-which is a phosphorylated protein.