Low molecular weight protein tyrosine phosphatase as signaling hub of cancer hallmarks

Diversified nanocarrier design to optimize glucose oxidase-mediated anti-tumor therapy: Strategy and progress

Given the inherent complexity and heterogeneity of tumors, current therapeutic approaches often fall short in meeting prognostic requirements. Starvation therapy (ST) utilizing glucose oxidase (GOx) has emerged as a promising strategy, specifically targeting tumor glucose consumption to disrupt nutrient supply. However, the therapeutic potential of GOx is significantly hampered by its inherent limitations as a protein, particularly its poor stability and short in vivo half-life. In recent years, the development of nanocarriors has provided an effective platform for intravenous and local tumor delivery of GOx. This review systematically examines three key strategies in GOx delivery: stimulus-response, biofilm modification, and local delivery. The progress in various carrier systems for GOx-mediated tumor therapy is comprehensively summarized, providing valuable insights for nanocarrier design. Furthermore, the existing challenges and future directions to advance the development of GOx-based tumor therapies are critically analyzed.

Dual-specific phosphatase DUSP21 is a novel negative feedback regulator for STAT3

Dual-specificity phosphatases (DUSPs) catalyze the dephosphorylation of tyrosine and serine/threonine residues in target proteins. Atypical DUSPs (aDUSPs) lack substrate-binding motifs, suggesting their potential to target a diverse array of substrates. This study demonstrated that DUSP21, an aDUSP, is induced by leukemia inhibitory factor (LIF) in HeLa cells and acts as a negative regulator of LIF-induced signal transducer and activator of transcription 3 (STAT3) activation. Overexpressed DUSP21 co-localized and interacted with STAT3 in HeLa cells. Recombinant DUSP21 directly dephosphorylated STAT3 in vitro. Additionally, DUSP21 overexpression modulated STAT3-dependent growth of Ba/F3-G133 cells. These findings indicate that LIF-induced DUSP21 exerts an inhibitory effect on the LIF/STAT3 signaling pathway, thereby functioning as a suppressor of STAT3-mediated transcriptional activity.

Genetic Modulation of HPV Infection and Cervical Lesions: Role of Oxidative Stress-Related Genes

Human papillomavirus (HPV) infection is a necessary but not sufficient factor for the development of invasive cervical cancer (ICC) and high-grade intraepithelial lesion (HSIL). Oxidative stress is known to play a crucial role in HPV infection and carcinogenesis. In this study, we comprehensively investigate the modulation of HPV infection, HSIL and ICC, and ICC through an exploration of oxidative stress-related genes: CβS, MTHFR, NOS3, ACE1, CYBA, HAP, ACP1, GSTT1, GSTM1, and CYP1A1. Notably, the ACE1 gene emerges as a prominent factor with the presence of the I allele offering protection against HPV infection. The association of NOS3 with HPV infection is perceived with the 4a allele showing a protective effect. The presence of the GSTT1 null mutant correlates with increased susceptibility to HPV infection, HSIL and ICC, and ICC. This study also uncovers intriguing epistatic interactions among some of the genes that further accentuate their roles in disease modulation. Indeed, the epistatic interactions between the BB genotype (ACP1) and DD genotype (ECA1) were shown to increase the risk of HPV infection, and the interaction between BB (ACP1) and 0.0 (GSTT1) was associated with HPV infection and cervical lesions. These findings underscore the pivotal role of four oxidative stress-related genes in HPV-associated cervical lesions and cancer development, enriching our clinical understanding of the genetic influences on disease manifestation. The awareness of these genetic variations holds potential clinical implications.

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.

Low molecular weight protein phosphatase APH mediates tyrosine dephosphorylation and ABA response in Arabidopsis

Low molecular weight protein tyrosine phosphatase (LWM-PTP), also known as acid phosphatase, is a highly conserved tyrosine phosphatase in living organisms. However, the function of LWM-PTP homolog has not been reported yet in plants. Here, we revealed a homolog of acid phosphatase, APH, in Arabidopsis plants, is a functional protein tyrosine phosphatase. The aph mutants are hyposensitive to ABA in post-germination growth. We performed an anti-phosphotyrosine antibody-based quantitative phosphoproteomics in wild-type and aph mutant and identified hundreds of putative targets of APH, including multiple splicing factors and other transcriptional regulators. Consistently, RNA-seq analysis revealed that the expression of ABA-highly-responsive genes is suppressed in aph mutants. Thus, APH regulates the ABA-responsive gene expressions by regulating the tyrosine phosphorylation of multiple splicing factors and other post-transcriptional regulators. We also revealed that Tyr383 in RAF9, a member of B2 and B3 RAF kinases that phosphorylate and activate SnRK2s in the ABA signaling pathway, is a direct target site of APH. Phosphorylation of Tyr383 is essential for RAF9 activity. Our results uncovered a crucial function of APH in ABA-induced tyrosine phosphorylation in Arabidopsis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s44154-022-00041-6.

Tyrosine Kinases and Phosphatases: Enablers of the Porphyromonas gingivalis Lifestyle

Tyrosine phosphorylation modifies the functionality of bacterial proteins and forms the basis of a versatile and tunable signal transduction system. The integrated action of tyrosine kinases and phosphatases controls bacterial processes important for metabolism and virulence. Porphyromonas gingivalis, a keystone pathogen in periodontal disease, possesses an extensive phosphotyrosine signaling network. The phosphorylation reaction is catalyzed by a bacterial tyrosine (BY) kinase, Ptk1, and a Ubiquitous bacterial Kinase UbK1. Dephosphorylation is mediated by a low-molecular-weight phosphatase, Ltp1 and a polymerase and histidinol phosphatase, Php1. Phosphotyrosine signaling controls exopolysaccharide production, gingipain activity, oxidative stress responses and synergistic community development with Streptococcus gordonii. Additionally, Ltp1 is secreted extracellularly and can be delivered inside gingival epithelial cells where it can override host cell signaling and readjust cellular physiology. The landscape of coordinated tyrosine kinase and phosphatase activity thus underlies the adaptive responses of P. gingivalis to both the polymicrobial environment of bacterial communities and the intracellular environment of gingival epithelial cells.

A Plasmodium falciparum protein tyrosine phosphatase inhibitor identified from the ChEMBL-NTD database blocks parasite growth

Post‐translational modifications, especially reversible phosphorylation, are among the most common mechanisms that regulate protein function and biological processes in Plasmodium species. Of the Plasmodium phosphatases, phosphatase of regenerating liver (PfPRL) is secreted and is an essential phosphatase. Here, we expressed PfPRL in a heterologous expression system, and then purified and characterized its phosphatase activity. We found that Novartis_003209, a previously identified inhibitor, inhibited the PfPRL phosphatase activity of recombinant PfPRL and blocked in vitro parasite growth in a dose‐dependent manner. Further, in silico docking analysis of Novartis_003209 with all four P. falciparum tyrosine phosphatases (PTP) demonstrated that Novartis_003209 is a Plasmodium PTP inhibitor. Overall, our results identify a scaffold as a potential starting point to design a PTP‐specific inhibitor.

A bacterial tyrosine phosphatase modulates cell proliferation through targeting RGCC

Tyrosine phosphatases are often weaponized by bacteria colonizing mucosal barriers to manipulate host cell signal transduction pathways. Porphyromonas gingivalis is a periodontal pathogen and emerging oncopathogen which interferes with gingival epithelial cell proliferation and migration, and induces a partial epithelial mesenchymal transition. P. gingivalis produces two tyrosine phosphatases, and we show here that the low molecular weight tyrosine phosphatase, Ltp1, is secreted within gingival epithelial cells and translocates to the nucleus. An ltp1 mutant of P. gingivalis showed a diminished ability to induce epithelial cell migration and proliferation. Ltp1 was also required for the transcriptional upregulation of Regulator of Growth and Cell Cycle (RGCC), one of the most differentially expressed genes in epithelial cells resulting from P. gingivalis infection. A phosphoarray and siRNA showed that P. gingivalis controlled RGCC expression through Akt, which was activated by phosphorylation on S473. Akt activation is opposed by PTEN, and P. gingivalis decreased the amount of PTEN in epithelial cells. Ectopically expressed Ltp1 bound to PTEN, and reduced phosphorylation of PTEN at Y336 which controls proteasomal degradation. Ltp-1 induced loss of PTEN stability was prevented by chemical inhibition of the proteasome. Knockdown of RGCC suppressed upregulation of Zeb2 and mesenchymal markers by P. gingivalis. RGCC inhibition was also accompanied by a reduction in production of the proinflammatory cytokine IL-6 in response to P. gingivalis. Elevated IL-6 levels can contribute to periodontal destruction, and the ltp1 mutant of P. gingivalis incited less bone loss compared to the parental strain in a murine model of periodontal disease. These results show that P. gingivalis can deliver Ltp1 within gingival epithelial cells, and establish PTEN as the target for Ltp1 phosphatase activity. Disruption of the Akt1/RGCC signaling axis by Ltp1 facilitates P. gingivalis-induced increases in epithelial cell migration, proliferation, EMT and inflammatory cytokine production.

Bacteria colonizing the oral cavity can induce inflammatory destruction of the periodontal tissues, and are increasingly associated with oral squamous cell carcinoma. P. gingivalis, a major periodontal pathogen, can subvert epithelial pathways that control important physiological processes relating to innate immunity and cell fate; however, little is known about the effector molecules. Here we show that P. gingivalis can deliver a tyrosine phosphatase, Ltp1, within epithelial cells, and Ltp1 phosphatase activity destabilizes PTEN, a negative regulator of Akt1 signaling. The production of RGCC is thus increased and this leads to increased epithelial cell migration, proliferation, a partial mesenchymal phenotype and inflammatory cytokine production. Ltp1 phosphatase activity thus provides a mechanistic basis for a number of P. gingivalis properties that contribute to disease. Indeed, an Ltp1-deficient mutant was less pathogenic in a murine model of periodontitis. These results contribute to deciphering the pathophysiological events that underlie oral bacterial diseases that initiate at mucosal barriers.