Search Results (46)

Polyphosphate (PolyP) is an inorganic polymer composed of orthophosphate units linked by high-energy phosphate anhydride bonds, widely found in various organisms from bacteria to mammals. In recent years, PolyP has attracted widespread attention in the field of bone tissue engineering due to its unique biological characteristics, possessing both osteoinductive activity and metabolic energy supply functions. This article systematically reviews the molecular structure, physicochemical properties, and multiple mechanisms by which PolyP promotes osteogenic differentiation, as well as biomaterial design strategies based on PolyP. PolyP can synergistically promote osteogenic differentiation through multiple mechanisms, including by acting as a phosphate donor, providing metabolic energy, regulating signaling pathways such as Wnt/β-catenin, and modulating the osteoprotegerin/receptor activator of nuclear factor κB ligand (OPG/RANKL) balance. In terms of material design, PolyP can form nano/microparticles with metal ions such as Ca²⁺, Sr²⁺, and Mg²⁺ and can also be compounded with polymers to construct various forms such as hydrogels, bone cement, and three-dimensional (3D)-printed scaffolds. Preclinical studies have shown that PolyP-incorporated materials exhibit excellent osteogenic performance and biocompatibility in bone defect repair, and preliminary clinical studies have also confirmed its feasibility. This article aims to provide a comprehensive overview of the current applications of PolyP-incorporated materials and delineate future directions, challenges, and necessary pathways for their clinical translation. Full article

Inorganic polyphosphate (polyP) is a ubiquitous polymer increasingly recognized as a regulator of protein function through lysine polyphosphate modification (KPM), a reversible interaction with lysine-rich protein regions. Although numerous KPM targets have been identified, the functional consequences of polyP binding remain poorly understood. N-myristoyltransferase 2 (NMT2), an essential enzyme that catalyzes protein N-myristoylation and regulates membrane-associated signaling pathways, was previously identified as a candidate KPM target. Here, we investigated the molecular and functional relationship between polyP and NMT2. Using a fluorescence-based coenzyme A release assay, we found that polyP directly down-regulated NMT2 enzymatic activity in a dose-dependent manner, with long-chain polyP (polyP₇₀₀) producing significantly greater inhibition than medium-chain polyP (polyP₁₀₀). In cells, both exogenous polyP treatment and induction of endogenous polyP synthesis reduced phosphorylation of Src, a downstream signaling protein whose activation depends on N-myristoylation, supporting inhibition of NMT2 function in vivo. PolyP also decreased the viability of NMT2-overexpressing HeLa cells in a dose-dependent manner, suggesting functional consequences for cellular fitness. Biochemical analysis further revealed that polyP induced a pronounced electrophoretic mobility shift in NMT2 that was completely reversed by a 25-residue lysine-rich competitor peptide, consistent with a specific and reversible interaction mediated through lysine-enriched regions of the enzyme. These findings identify NMT2 as a functional target of polyP and demonstrate that polyP negatively regulates NMT2 activity, downstream Src signaling, and cellular viability. Our results expand the emerging concept of lysine polyphosphate modification and establish polyP as a previously unrecognized regulator of protein lipidation-dependent signaling pathways. Full article

Inorganic polyphosphates (polyP) are linear phosphate polymers that play essential functions in human physiology, such as coagulation and inflammation. Despite their recognized participation in solid tumor progression, there are few data on hematolymphoid malignancies. Here, we conducted a narrative review of studies investigating polyP functions in mammalian biology, coagulation, and hematologic systems, focusing on research gaps in hematological oncology. PolyP modulates coagulation cascades, platelet activation, and cellular metabolism. In tumors, polyP has been reported to modulate immune responses and apoptosis in several experimental systems. Emerging data suggest participation in leukemic signaling and the bone marrow microenvironment. Direct evidence linking polyP to hematolymphoid neoplasms is scarce. Being biologically plausible, it represents a promising and largely unexplored area of research and an excellent opportunity for novel therapeutic approaches. Full article

Inorganic polyphosphate is highly conserved, critical, yet poorly understood polymer that regulates diverse cellular functions in mammals. Its importance is well established in coagulation, inflammation, mitochondrial function, and stress responses, though the molecular mechanisms for these effects remain only partly understood. Fundamental questions also persist regarding its physiological concentration, chain-length distributions, and the mechanisms that regulate its behavior in specific cellular compartments. Progress is limited by the absence of a known mammalian polyphosphate-synthesizing enzyme. Despite this, recent studies have broadened the scope of polyphosphate biology, suggesting roles in protein phase separation, ATP-independent chaperone activity, metabolic regulation, and intracellular signaling. Polyphosphate modulates the mitochondrial permeability transition pore through calcium-dependent regulation and activates factor XII in coagulation. Findings have also introduced potential connections between polyphosphate and processes such as neurodegeneration, cancer, and tissue regeneration. Despite this expanding landscape, many biological effects remain difficult to interpret due to incomplete mapping of protein targets and longstanding technical limitations in detecting and quantifying polyP. This review integrates molecular protein-interaction mechanisms with compartment-specific functions and disease physiology, providing a clearer mechanistic framework while identifying key conceptual and methodological gaps and outlining priorities for advancing polyphosphate research in mammalian systems. Full article

Chemorepulsion mechanisms for eukaryotic cells are poorly understood. We performed proteomics and phosphoproteomics to elucidate how Dictyostelium discoideum responds to its two endogenous chemorepellent signals, the protein AprA and inorganic polyphosphate (polyP). AprA and polyP affected levels of more than 200 proteins, with an overlap of both upregulating 25 proteins and downregulating two proteins. Two proteins were upregulated by AprA but downregulated by polyP, while two others showed the opposite trend. Surprisingly, many of the AprA- and polyP-regulated proteins are associated with RNA metabolism and ribosomes. AprA increased phosphorylation of 15 proteins and decreased phosphorylation of 36 proteins. PolyP increased phosphorylation of 12 proteins and decreased phosphorylation of 12 proteins. As expected, the two chemorepellents affected phosphorylation of signal transduction/ motility proteins, but unexpectedly affected phosphorylation of RNA-associated proteins. Both AprA and polyP decreased phosphorylation of five proteins including the Ras-interacting protein RipA and guanine nucleotide exchange factors (GEFs) such as the RacGEF GxcT. Mutants lacking RipA or GxcT were unresponsive to both AprA and polyP chemorepulsion. Together, this work supports the idea that rather than activating the same chemorepulsion mechanism, AprA and polyP activate only partially overlapping chemorepulsion mechanisms, and identifies two new components that are used by both chemorepellents. Full article

Myofibroblasts drive wound healing and fibrotic disease through generation of contractile force to promote wound closure and production of matrix proteins to generate scar tissue. Platelets secrete many pro-wound healing molecules, including cytokines and growth factors. We previously reported that inorganic polyphosphate, secreted by activated platelets, is chemotactic for fibroblasts and induces a myofibroblast phenotype. Using NIH-3T3 cells and primary human fibroblasts, we examined the impact of inhibitors of cell-surface receptors and intracellular signaling molecules on polyphosphate-induced myofibroblast differentiation. We now report that polyphosphate-induced differentiation of fibroblasts to myofibroblasts occurs through a signaling pathway mediated by the receptor for advanced glycation end products (RAGE) and nuclear factor kappa B (NFκB) transcription factor. Inhibition of these signaling components ablated the effects of polyphosphate on fibroblasts. Platelet releasates also induced NFκB signaling and myofibroblast differentiation. Blocking the polyphosphate content of platelet releasates with a biocompatible polyP inhibitor rendered the releasates unable to induce myofibroblast differentiation. These results identify a cell-surface receptor and intracellular transcription factor utilized by platelet polyphosphate to promote wound healing through myofibroblast differentiation and may provide targets for promoting wound healing or altering the disease progression of fibrosis. Full article

Chromosome transmission fidelity is vital for organism fitness. Yet, extrinsic and intrinsic changes can affect this process, leading to aneuploidy, the loss/gain of chromosomes, which is a hallmark of cancer. Here, using a haploid fission yeast Schizosaccharomyces pombe strain with a segmental aneuploidy, we assayed genome stability under different temperatures and altered gene dosage. We find that S. pombe genome stability is temperature-dependent and is unexpectedly modulated by intracellular levels of inorganic polyphosphate polymers (polyP). The vtc4⁺ gene, encoding a subunit of the polyP-generating VTC complex, is present twice due to the segmental aneuploidy resulting in a gene-dosage-coupled increase in polyP. Using strains with different amounts of polyP, we find a direct negative correlation between polyP and chromosome segregation fidelity. PolyP modulates the function of the conserved CCAN kinetochore subcomplex, as the abnormal growth phenotype caused by the mutant CCAN protein Fta2-291 was rescued in the absence of polyP, while extra polyP had the opposite effect. Importantly, this appears to occur in part by modulation of the nucleolin Gar2. Gar2 is the functional homolog of the Saccharomyces cerevisiae Nsr1 protein, whose function is modulated by posttranslational polyP-mediated polyphosphorylation. Thus, polyP modulates genome stability, linking cellular metabolism to chromosome transmission fidelity. Full article

Inorganic polyphosphate (iPolyP) is a ubiquitous molecule composed of a variable number of orthophosphate units. Recent studies have highlighted its involvement in colorectal cancer (CRC) cell proliferation. However, further investigations are needed to elucidate its role in CRC cell progression and migration, as well as its influence on the tumor microenvironment. This study focuses on the inorganic polyphosphate (iPolyP)/transient receptor potential cation channel subfamily M member 8 (TRPM8) axis and its impact on CRC progression. To investigate these issues, western blotting, fixed and live cells immunofluorescence, 2D and 3D cell culture on CRC-patient derived tissues, ELISA, and wound healing assays were performed. Our results show that inorganic polyphosphate induces the expression of epithelial-to-mesenchymal transition (EMT) markers in CRC cells. Furthermore, the iPolyP/TRPM8 axis indirectly promotes tumor growth through activation of the Nucleotide-binding oligomerization domain, Leucine-rich Repeat and Pyrin domain-containing protein 3 (NLRP3) inflammasome in immune cells, leading to increased levels of the pro-inflammatory cytokine interleukin-1β (IL-1β) in the tumor microenvironment (TME), thereby advancing CRC. These findings suggest that targeting the iPolyP/TRPM8 pathway may be a promising strategy to inhibit CRC progression and metastasis. Full article

Inorganic polyphosphate (polyP) is an evolutionarily conserved polymer that has recently gained relevance in neuronal physiology and pathophysiology. Although its roles, such as mitochondrial bioenergetics, calcium homeostasis, and the oxidative stress response, for example, are increasingly recognized, its specific implications in neurological disorders remain underexplored. This review focuses on synthesizing the current knowledge of polyP in the context of central nervous system (CNS) diseases, highlighting how its involvement in key mitochondrial processes may influence neuronal survival and function. In particular, we examine recent evidence linking polyP to mechanisms relevant to neurodegeneration, such as the modulation of the mitochondrial permeability transition pore (mPTP), regulation of amyloid fibril formation, and oxidative stress responses. In addition, we analyze the emerging roles of polyP in inflammation and related cell signaling in CNS disorders. By organizing the existing data around the potential pathological and protective roles of polyP in the CNS, this review identifies it as a candidate of interest in the context of neurodegenerative disease mechanisms. We aim to clarify its relevance and stimulate future research on its molecular mechanisms and translational potential. Full article

Inorganic polyphosphate (PolyP) is a high-molecular-weight polymer that plays multiple roles in regulating immune responses. However, the specific anti-inflammatory mechanisms of bacteria-derived PolyP are unclear. In the present study, PolyP was extracted from Lactobacillus plantarum (L. plantarum), and the chain length was estimated to be approximately 250 Pi residues. The immune regulatory functions of PolyP were investigated using a lipopolysaccharide (LPS)-induced RAW264.7 cell oxidative stress model, and dexamethasone was used as a positive control. The result revealed that both dexamethasone and PolyP were protective against oxidative stress by inhibiting macrophage M1 polarization and the production of several markers, such as nitric oxide (NO), reactive oxygen species (ROS), inducible nitric oxide synthase (iNOS), and cyclooxygenase (COX)-2. In addition, PolyP suppressed inflammation progression by regulating the production of several cytokines, such as interleukin (IL)-1β, interferon (INF)-γ, tumor necrosis factor (TNF)-α, and IL-6, and inhibited the expressions of inhibitory κB kinase (IKK) α, IKKβ, and extracellular regulated protein kinases 2 (ERK2). Conclusively, PolyP derived from L. plantarum has the ability to protect cells from oxidative stress damage by inhibiting M1 polarization in macrophages. These findings provide insights into the function of PolyP and offer support for the potential application of PolyP in immune-related diseases. Full article

Polyphosphates are biopolymers composed of phosphate monomers linked by high-energy phosphoanhydride bonds. They are present across all life domains, serving as a source of energy, metal chelators, and playing a crucial role in stress defense. In Escherichia coli, polyphosphates also function as inorganic molecular chaperones. The present study aims to investigate whether polyphosphate serves a similar chaperone function in archaea, using Saccharolobus solfataricus as a model organism. To this end, polyphosphate was extracted and quantified, the ADP/ATP ratio was determined, insoluble protein extracts were analyzed at different time points after copper exposure, and qPCR was performed to measure the expression of stress-related genes. PolyP was extracted after exposing the archaeon S. solfataricus to different copper concentrations. We determined that polyP degradation is directly correlated with metal concentration. At the minimum inhibitory concentration (MIC) of 2 mM Cu²⁺, polyP degradation stabilized 2 h after exposure and showed no recovery even after 24 h. The ADP/ATP ratio was measured and showed differences in the presence or absence of polyP. The analysis of proteins precipitated under copper stress showed a higher proportion of insoluble proteins at an elevated metal concentration. On the other hand, increased protein precipitation was detected in the absence of polyP. Gene expression analysis via qPCR was conducted to assess the expression of genes involved in chaperone and chaperonin production, copper resistance, oxidative stress response, and phosphate metabolism under prolonged copper exposure, both in the presence and absence of polyP. The results indicated an upregulation of all the chaperonins measured in the presence of polyP. Interestingly, just some of these genes were upregulated in polyP’s absence. Despite copper stress, there was no upregulation of superoxide dismutase in our conditions. These results highlight the role of polyP in the copper stress response in S. solfataricus, particularly to prevent protein precipitation, likely due to its function as an inorganic chaperone. Additionally, the observed protein precipitation could be attributable to interactions between copper and some amino acids on the protein structures rather than oxidative stress induced by copper exposure, as previously described in E. coli. Our present findings provide new insights into the protective role of polyP as an inorganic chaperone in S. solfataricus and emphasize its importance in maintaining cellular homeostasis under metal stress conditions. Full article

Background: Colorectal cancer (CRC) is characterized by a pro-inflammatory microenvironment and features high-energy-supply molecules that assure tumor growth. A still less studied macromolecule is inorganic polyphosphate (iPolyP), a high-energy linear polymer that is ubiquitous in all forms of life. Made up of hundreds of repeated orthophosphate units, iPolyP is essential for a wide variety of functions in mammalian cells, including the regulation of proliferative signaling pathways. Some evidence has suggested its involvement in carcinogenesis, although more studies need to be pursued. Moreover, iPolyP regulates several homeostatic processes in animals, spanning from energy metabolism to blood coagulation and tissue regeneration. Results: In this study, we tested the role of iPolyP on CRC proliferation, using in vitro and ex vivo approaches, in order to evaluate its effect on tumor growth. We found that iPolyP is significantly increased in tumor tissues, derived from affected individuals enrolled in this study, compared to the corresponding peritumoral counterparts. In addition, iPolyP signaling occurs through the TRPM8 receptor, a well-characterized Na⁺ and Ca²⁺ ion channel often overexpressed in CRC and linked with poor prognosis, thus promoting CRC cell proliferation. The pharmacological inhibition of TRPM8 or RNA interference experiments performed in established CRC cell lines, such as Caco-2 and SW620, showed that the involvement of TRPM8 is essential, greater than that of the other two known iPolyP receptors, P2Y1 and RAGE. The presence of iPolyP drives cancer cells towards the mitotic phase of the cell cycle by enhancing the expression of ccnb1, which encodes the Cyclin B protein. In vitro 2D and 3D data reflected the ex vivo results, obtained by the generation of CRC-derived organoids, which increased in size. Conclusions: These results indicate that iPolyP may be considered a novel and unexpected early biomarker supporting colorectal cancer cell proliferation. Full article

Trypanosoma cruzi is the etiologic agent of Chagas disease, an infection that can lead to the development of cardiac fibrosis, which is characterized by the deposition of extracellular matrix (ECM) components in the interstitial region of the myocardium. The parasite itself can induce myofibroblast differentiation of cardiac fibroblast in vitro, leading to increased expression of ECM. Inorganic polyphosphate (polyP) is a linear polymer of orthophosphate that can also induce myofibroblast differentiation and deposition of ECM components and is highly abundant in T. cruzi. PolyP can modify proteins post-translationally by non-enzymatic polyphosphorylation of lysine residues of poly-acidic, serine-(S) and lysine (K)-rich (PASK) motifs. In this work, we used a bioinformatics screen and identified the presence of PASK domains in several surface proteins of T. cruzi. We also detected polyP in the external surface of its different life cycle stages and confirmed the stimulation of host cell fibrosis by trypomastigote infection. However, we were not able to detect significant secretion of the polymer or activation of transforming growth factor beta (TGF-β), an important factor for the generation of fibrosis by inorganic polyP- or trypomastigote-conditioned medium. Full article

Polyphosphate (polyP) is an evolutionary ancient inorganic molecule widespread in biology, exerting a broad range of biological activities. The intracellular polymer serves as an energy storage pool and phosphate/calcium ion reservoir with implications for basal cellular functions. Metabolisms of the polymer are well understood in procaryotes and unicellular eukaryotic cells. However, functions, regulation, and association with disease states of the polymer in higher eukaryotic species such as mammalians are just beginning to emerge. The review summarises our current understanding of polyP metabolism, the polymer’s functions, and methods for polyP analysis. In-depth knowledge of the pathways that control polyP turnover will open future perspectives for selective targeting of the polymer. Full article

The PHO91 and PHO87 are parts of yeast’s phosphate metabolism system. We investigated the influence of PHO91 deletion on the methanol utilization as a sole carbon source in Ogataea parapolymorpha through comparison of wet biomass, protein content, methanol oxidase (MOX) activity and acid-soluble and acid-insoluble inorganic polyphosphate (polyP) content, while growing on methanol and without any carbon source other than trace amounts from the yeast extract. The Δpho91 strain has a lack of wet biomass, protein content and MOX activity while grown on methanol (as a ΔMOX strain) and has the same numbers as a WT strain in media without methanol. We found two ways of recovering methanol utilizing capabilities for Δpho91 mutant—either adding MOX on plasmid under constitutive promoter control, or adding a Δpho87 mutation. Both Δpho91 + MOX and Δpho91Δpho87 strains showed all the parameters as a WT strain on methanol as a sole carbon source and without methanol addition. Further, we compare the polyP content of the strains in methanol media, media without a sole carbon source and media with glucose. All of the WT, Δpho91 + MOX and Δpho91Δpho87 strains, capable of utilizing methanol, have the P_i, acid-soluble and acid-insoluble polyP at the same levels with some variations. The ΔMOX and Δpho91 strains, despite both not being able to utilize methanol, showed very different levels of P_i and polyP’s, which can be interpreted as different mechanisms of the inner cell, leading to a loss of capability utilizing methanol in both of these strains. Full article