Computational analysis reveals a successive adaptation of multiple inositol polyphosphate phosphatase 1 in higher organisms through evolution

Depleting inositol pyrophosphate 5-InsP7 protected the heart against ischemia-reperfusion injury by elevating plasma adiponectin

AIMS

Adiponectin is an adipocyte-derived circulating protein that exerts cardiovascular and metabolic protection. Due to the futile degradation of endogenous adiponectin and the challenges of exogenous administration, regulatory mechanisms of adiponectin biosynthesis are of significant pharmacological interest.

METHODS AND RESULTS

Here, we report that 5-diphosphoinositol 1,2,3,4,6-pentakisphosphate (5-InsP7) generated by inositol hexakisphosphate kinase 1 (IP6K1) governed circulating adiponectin levels via thiol-mediated protein quality control in the secretory pathway. IP6K1 bound to adiponectin and DsbA-L and generated 5-InsP7 to stabilize adiponectin/ERp44 and DsbA-L/Ero1-Lα interactions, driving adiponectin intracellular degradation. Depleting 5-InsP7 by either IP6K1 deletion or pharmacological inhibition blocked intracellular adiponectin degradation. Whole-body and adipocyte-specific deletion of IP6K1 boosted plasma adiponectin levels, especially its high molecular weight forms, and activated AMPK-mediated protection against myocardial ischemia-reperfusion injury. Pharmacological inhibition of 5-InsP7 biosynthesis in WT but not adiponectin knockout mice attenuated myocardial ischemia-reperfusion injury.

CONCLUSIONS

Our findings revealed that 5-InsP7 is a physiological regulator of adiponectin biosynthesis that is amenable to pharmacological intervention for cardioprotection.

Wheat phytase potentially protects HT-29 cells from inflammatory nucleotides-induced cytotoxicity

OBJECTIVE

The aim of this study was to investigate the protective effect of wheat phytase as a structural decomposer of inflammatory nucleotides, extracellular adenosine triphosphate (ATP), and uridine diphosphate (UDP) on HT-29 cells.

METHODS

Phosphatase activities of wheat phytase against ATP and UDP was investigated in the presence or absence of inhibitors such as L-phenylalanine and L-homoarginine using a Pi Color Lock gold phosphate detection kit. Viability of HT-29 cells exposed to intact- or dephosphorylated-nucleotides was analyzed with an EZ-CYTOX kit. Secretion levels of pro-inflammatory cytokines (IL-6 and IL-8) in HT-29 cells exposed to substrate treated with or without wheat phytase were measured with enzyme-linked immunosorbent assay kits. Activation of caspase-3 in HT-29 cells treated with intact ATP or dephosphorylated-ATP was investigated using a colorimetric assay kit.

RESULTS

Wheat phytase dephosphorylated both nucleotides, ATP and UDP, in a dosedependent manner. Regardless of the presence or absence of enzyme inhibitors (L-phenylalanine and L-homoarginine), wheat phytase dephosphorylated UDP. Only L-phenylalanine inhibited the dephosphorylation of ATP by wheat phytase. However, the level of inhibition was less than 10%. Wheat phytase significantly enhanced the viability of HT-29 cells against ATP- and UDP-induced cytotoxicity. Interleukin (IL)-8 released from HT-29 cells with nucleotides dephosphorylated by wheat phytase was higher than that released from HT-29 cells with intact nucleotides. Moreover, the release of IL-6 was strongly induced from HT-29 cells with UDP dephosphorylated by wheat phytase. HT-29 cells with ATP degraded by wheat phytase showed significantly (13%) lower activity of caspase-3 than HT-29 cells with intact ATP.

CONCLUSION

Wheat phytase can be a candidate for veterinary medicine to prevent cell death in animals. In this context, wheat phytase beyond its nutritional aspects might be a novel and promising tool for promoting growth and function of intestinal epithelial cells under luminal ATP and UDP surge in the gut.

Stable Isotopomers of myo-Inositol Uncover a Complex MINPP1-Dependent Inositol Phosphate Network

The water-soluble inositol phosphates (InsPs) represent a functionally diverse group of small-molecule messengers involved in a myriad of cellular processes. Despite their centrality, our understanding of human InsP metabolism is incomplete because the available analytical toolset to characterize and quantify InsPs in complex samples is limited. Here, we have synthesized and applied symmetrically and unsymmetrically ¹³C-labeled myo-inositol and inositol phosphates. These probes were utilized in combination with nuclear magnetic resonance spectroscopy (NMR) and capillary electrophoresis mass spectrometry (CE-MS) to investigate InsP metabolism in human cells. The labeling strategy provided detailed structural information via NMR-down to individual enantiomers-which overcomes a crucial blind spot in the analysis of InsPs. We uncovered a novel branch of InsP dephosphorylation in human cells which is dependent on MINPP1, a phytase-like enzyme contributing to cellular homeostasis. Detailed characterization of MINPP1 activity in vitro and in cells showcased the unique reactivity of this phosphatase. Our results demonstrate that metabolic labeling with stable isotopomers in conjunction with NMR spectroscopy and CE-MS constitutes a powerful tool to annotate InsP networks in a variety of biological contexts.

Identification and functional characterization of multiple inositol polyphosphate phosphatase1 (Minpp1) isoform-2 in exosomes with potential to modulate tumor microenvironment

Inositol polyphosphates (InsPs) play key signaling roles in diverse cellular functions, including calcium homeostasis, cell survival and death. Multiple inositol polyphosphate phosphatase 1 (Minpp1) affects the cellular levels of InsPs and cell functions. The Minpp1 is an endoplasmic reticulum (ER) resident but localizes away from its cytosolic InsPs substrates. The current study examines the heterogeneity of Minpp1 and the potential physiologic impact of Minpp1 isoforms, distinct motifs, subcellular distribution, and enzymatic potential. The NCBI database was used to analyze the proteome diversity of Minpp1 using bioinformatics tools. The analysis revealed that translation of three different Minpp1 variants resulted in three isoforms of Minpp1 of varying molecular weights. A link between the minpp1 variant-2 gene and ER-stress, using real-time PCR, suggests a functional similarity between minpp1 variant-1 and variant-2. A detailed study on motifs revealed Minpp1 isoform-2 is the only other isoform, besides isoform-1, that carries a phosphatase motif for InsPs hydrolysis but no ER-retention signal. The confocal microscopy revealed that the Minpp1 isoform-1 predominantly localized near the nucleus with a GRP-78 ER marker, while Minpp1 isoform-2 was scattered more towards the cell periphery where it co-localizes with the plasma membrane-destined multivesicular bodies biomarker CD63. MCF-7 cells were used to establish that Minpp1 isoform-2 is secreted into exosomes. Brefeldin A treatment resulted in overexpression of the exosome-associated Minpp1 isoform-2, suggesting its secretion via an unconventional route involving endocytic-generated vesicles and a link to ER stress. Results further demonstrated that the exosome-associated Minpp1 isoform-2 was enzymatically active. Overall, the data support the possibility that an extracellular form of enzymatically active Minpp1 isoform-2 mitigates any anti-proliferative actions of extracellular InsPs, thereby also impacting the makeup of the tumor microenvironment.

Wheat phytase can alleviate the cellular toxic and inflammatory effects of lipopolysaccharide

The objective of this study was to characterize the enzymatic hydrolysis of lipopolysaccharide (LPS) by wheat phytase and to investigate the effects of wheat phytase-treated LPS on in vitro toxicity, cell viability and release of a pro-inflammatory cytokine, interleukin (IL)-8 by target cells compared with the intact LPS. The phosphatase activity of wheat phytase towards LPS was investigated in the presence or absence of inhibitors such as L-phenylalanine and L-homoarginine. In vitro toxicity of LPS hydrolyzed with wheat phytase in comparison to intact LPS was assessed. Cell viability in human aortic endothelial (HAE) cells exposed to LPS treated with wheat phytase in comparison to intact LPS was measured. The release of IL-8 in human intestinal epithelial cell line, HT-29 cells applied to LPS treated with wheat phytase in comparison to intact LPS was assayed. Wheat phytase hydrolyzed LPS, resulting in a significant release of inorganic phosphate for 1 h (p < 0.05). Furthermore, the degradation of LPS by wheat phytase was nearly unaffected by the addition of L-phenylalanine, the inhibitor of tissue-specific alkaline phosphatase or L-homoarginine, the inhibitor of tissue-non-specific alkaline phosphatase. Wheat phytase effectively reduced the in vitro toxicity of LPS, resulting in a retention of 63% and 54% of its initial toxicity after 1–3 h of the enzyme reaction, respectively (p < 0.05). Intact LPS decreased the cell viability of HAE cells. However, LPS dephosphorylated by wheat phytase counteracted the inhibitory effect on cell viability. LPS treated with wheat phytase decreased IL-8 secretion from intestinal epithelial cell line, HT-29 cell to 14% (p < 0.05) when compared with intact LPS. In conclusion, wheat phytase is a potential therapeutic candidate and prophylactic agent for control of infections induced by pathogenic Gram-negative bacteria and associated LPS-mediated inflammatory diseases in animal husbandry.

Transcriptomic analysis of the honey bee (Apis mellifera) queen spermathecae reveals genes that may be involved in sperm storage after mating

Honey bee (Apis mellifera) queens have a remarkable organ, the spermatheca, which successfully stores sperm for years after a virgin queen mates. This study uniquely characterized and quantified the transcriptomes of the spermathecae from mated and virgin honey bee queens via RNA sequencing to identify differences in mRNA levels based on a queen's mating status. The transcriptome of drone semen was analyzed for comparison. Samples from three individual bees were independently analyzed for mated queen spermathecae and virgin queen spermathecae, and three pools of semen from ten drones each were collected from three separate colonies. In total, the expression of 11,233 genes was identified in mated queen spermathecae, 10,521 in virgin queen spermathecae, and 10,407 in drone semen. Using a cutoff log2 fold-change value of 2.0, we identified 212 differentially expressed genes between mated and virgin spermathecal queen tissues: 129 (1.4% of total) were up-regulated and 83 (0.9% of total) were down-regulated in mated queen spermathecae. Three genes in mated queen spermathecae, three genes in virgin queen spermathecae and four genes in drone semen that were more highly expressed in those tissues from the RNA sequencing data were further validated by real time quantitative PCR. Among others, expression of Kielin/chordin-like and Trehalase mRNAs was highest in the spermathecae of mated queens compared to virgin queen spermathecae and drone semen. Expression of the mRNA encoding Alpha glucosidase 2 was higher in the spermathecae of virgin queens. Finally, expression of Facilitated trehalose transporter 1 mRNA was greatest in drone semen. This is the first characterization of gene expression in the spermathecae of honey bee queens revealing the alterations in mRNA levels within them after mating. Future studies will extend to other reproductive tissues with the purpose of relating levels of specific mRNAs to the functional competence of honey bee queens and the colonies they head.

Snapshots during the catalytic cycle of a histidine acid phytase reveal an induced-fit structural mechanism

Highly engineered phytases, which sequentially hydrolyze the hexakisphosphate ester of inositol known as phytic acid, are routinely added to the feeds of monogastric animals to improve phosphate bioavailability. New phytases are sought as starting points to further optimize the rate and extent of dephosphorylation of phytate in the animal digestive tract. Multiple inositol polyphosphate phosphatases (MINPPs) are clade 2 histidine phosphatases (HP2P) able to carry out the stepwise hydrolysis of phytate. MINPPs are not restricted by a strong positional specificity making them attractive targets for development as feed enzymes. Here, we describe the characterization of a MINPP from the Gram-positive bacterium Bifidobacterium longum (BlMINPP). BlMINPP has a typical HP2P-fold but, unusually, possesses a large α-domain polypeptide insertion relative to other MINPPs. This insertion, termed the U-loop, spans the active site and contributes to substrate specificity pockets underpopulated in other HP2Ps. Mutagenesis of U-loop residues reveals its contribution to enzyme kinetics and thermostability. Moreover, four crystal structures of the protein along the catalytic cycle capture, for the first time in an HP2P, a large ligand-driven α-domain motion essential to allow substrate access to the active site. This motion recruits residues both downstream of a molecular hinge and on the U-loop to participate in specificity subsites, and mutagenesis identified a mobile lysine residue as a key determinant of positional specificity of the enzyme. Taken together, these data provide important new insights to the factors determining stability, substrate recognition, and the structural mechanism of hydrolysis in this industrially important group of enzymes.

Potential immune-modulatory effects of wheat phytase on the performance of a mouse macrophage cell line, Raw 264.7, exposed to long-chain inorganic polyphosphate

Objective

This experiment was conducted to find out the immunological effects of wheat phytase when long-chain inorganic polyphosphate (polyP) treated with wheat phytase was added to a macrophage cell line, Raw 264.7, when compared to intact long-chain polyP.

Methods

Nitric oxide (NO) production of Raw 264.7 cells exposed to P700, a long-chain polyP with an average of 1,150 phosphate residues, treated with or without wheat phytase, was measured by Griess method. Phagocytosis assay of P700 treated with or without phytase in Raw 264.7 cells was investigated using neutral red uptake. The secretion of tumor necrosis factor α (TNF-α) by Raw 264.7 cells with wheat phytase-treated P700 compared to intact P700 was observed by using Mouse TNF-α enzyme-linked immunosorbent assay kit.

Results

P700 treated with wheat phytase effectively increased NO production of Raw 264.7 cells by 172% when compared with intact P700 at 12 h exposure. At 5 mM of P700 concentration, wheat phytase promoted NO production of macrophages most strongly. P700, treated with wheat phytase, stimulated phagocytosis in macrophages at 12 h exposure by about 1.7-fold compared to intact P700. In addition, P700 treated with wheat phytase effectively increased in vitro phagocytic activity of Raw 264.7 cells at a concentration above 5 mM when compared to intact P700. P700 dephosphorylated by wheat phytase increased the release of TNF-α from Raw 264.7 cells by 143% over that from intact P700 after 6 h exposure. At the concentration of 50 μM P700, wheat phytase increased the secretion of cytokine, TNF-α, by 124% over that from intact P700.

Conclusion

In animal husbandry, wheat phytase can mitigate the long-chain polyP causing damage by improving the immune capabilities of macrophages in the host. Thus, wheat phytase has potential as an immunological modulator and future feed additive for regulating immune responses caused by inflammation induced by long-chain polyP from bacterial infection.

Impact of polyethylene on salivary glands proteome in Galleria melonella

Polyethylene pollutions are considered inert in nature and adversely affect the entire ecosystem. Larvae of greater wax moth (Galleria mellonella) have the ability to masticate and potentially biodegrade polyethylene films at elevated rates. The wax moth has been thought to metabolize PE independently of gut flora, however the role of the microbiome is poorly understood and degradation by the wax moth might be involved. To determine whether the salivary glands of the wax moth were potentially involved in the PE degradation, it was investigated how surface changes of polyethylene were affected by mastication and consumption. Formation of pitting and degradation intermediates including carbonyl groups, indicated that salivary glands could assist in polyethylene degradation. We investigated the biochemical effect of exposure by PE on the composition of the salivary gland proteome. The expression of salivary proteins was found to be affected by PE exposure. The proteins that were significantly affected by the exposure to PE revealed that the wax moth are undergoing general changes in energy levels, also enzymatic pathways associated to fatty acid beta oxidation during consumption to PE were induced.

Polymorphisms and genetic effects of PRLR, MOGAT1, MINPP1 and CHUK genes on milk fatty acid traits in Chinese Holstein

BACKGROUND

Our initial genome-wide association study (GWAS) identified 20 promising candidate genes for milk fatty acid (FA) traits in a Chinese Holstein population, including PRLR, MOGAT1, MINPP1 and CHUK genes. In this study, we performed whether they had significant genetic effects on milk FA traits in Chinese Holstein.

RESULTS

We re-sequenced the entire exons and 3000 bp of the 5' and 3' flanking regions, and identified 11 single nucleotide polymorphisms (SNPs), containing four in PRLR, two in MOGAT1, two in MINPP1, and three in CHUK. The SNP-based association analyses showed that all the 11 SNPs were significantly associated with at least one milk FA trait (P = 0.0456 ~ < 0.0001), and none of them had association with C11:0, C13:0, C15:0 and C16:0 (P > 0.05). By the linkage disequilibrium (LD) analyses, we found two, one, one, and one haplotype blocks in PRLR, MOGAT1, MINPP1, and CHUK, respectively, and each haplotype block was significantly associated with at least one milk FA trait (P = 0.0456 ~ < 0.0001). Further, g.38949011G > A in PRLR, and g.111599360A > G and g.111601747 T > A in MOGAT1 were predicted to alter the transcription factor binding sites (TFBSs). A missense mutation, g.39115344G > A, could change the PRLR protein structure. The g.20966385C > G of CHUK varied the binding sequences for microRNAs. Therefore, we deduced the five SNPs as the potential functional mutations.

CONCLUSION

In summary, we first detected the genetic effects of PRLR, MOGAT1, MINPP1 and CHUK genes on milk FA traits, and researched the potential functional mutations. These data provided the basis for further investigation on function validation of the four genes in Chinese Holstein.

Catalytic properties of wheat phytase that favorably degrades long-chain inorganic polyphosphate

Objective

This study was conducted to determine catalytic properties of wheat phytase with exopolyphosphatase activity toward medium-chain and long-chain inorganic polyphosphate (polyP) substrates for comparative purpose.

Methods

Exopolyphosphatase assay of wheat phytase toward polyP75 (medium-chain polyP with average 75 phosphate residues) and polyP1150 (long-chain polyP with average 1150 phosphate residues) was performed at pH 5.2 and pH 7.5. Its activity toward these substrates was investigated in the presence of Mg²⁺, Ni²⁺, Co²⁺, Mn²⁺, or ethylenediaminetetraacetic acid (EDTA). Michaelis constant (K_m) and maximum reaction velocity (V_max) were determined from Lineweaver-Burk plot with polyP75 or polyP1150. Monophosphate esterase activity toward p-nitrophenyl phosphate (pNPP) was assayed in the presence of polyP75 or polyP1150.

Results

Wheat phytase dephosphorylated polyP75 and polyP1150 at pH 7.5 more effectively than that at pH 5.2. Its exopolyphosphatase activity toward polyP75 at pH 5.2 was 1.4-fold higher than that toward polyP1150 whereas its activity toward polyP75 at pH 7.5 was 1.4-fold lower than that toward polyP1150. Regarding enzyme kinetics, K_m for polyP75 was 1.4-fold lower than that for polyP1150 while V_max for polyP1150 was 2-fold higher than that for polyP75. The presence of Mg²⁺, Ni²⁺, Co²⁺, Mn²⁺, or EDTA (1 or 5 mM) exhibited no inhibitory effect on its activity toward polyP75. Its activity toward polyP1150 was inhibited by 1 mM of Ni²⁺ or Co²⁺ and 5 mM of Ni²⁺, Co²⁺, or Mg²⁺. Ni²⁺ inhibited its activity toward polyP1150 the most strongly among tested additives. Both polyP75 and polyP1150 inhibited the monophosphate esterase activity of wheat phytase toward pNPP in a dose-dependent manner.

Conclusion

Wheat phytase with an unexpected exopolyphosphatase activity has potential as a therapeutic tool and a next-generational feed additive for controlling long-chain polyP-induced inappropriate inflammation from Campylobacter jejuni and Salmonella typhimurium infection in public health and animal husbandry.

Endoplasmic reticulum stress-induced apoptosis accompanies enhanced expression of multiple inositol polyphosphate phosphatase 1 (Minpp1): a possible role for Minpp1 in cellular stress response

Inositol polyphosphates represent a group of differentially phosphorylated inositol metabolites, many of which are implicated to regulate diverse cellular processes such as calcium mobilization, vesicular trafficking, differentiation, apoptosis, etc. The metabolic network of these compounds is complex and tightly regulated by various kinases and phosphatases present predominantly in the cytosol. Multiple inositol polyphosphate phosphatase 1 (Minpp1) is the only known endoplasmic reticulum (ER) luminal enzyme that hydrolyzes various inositol polyphosphates in vitro as well as in vivo conditions. However, access of the Minpp1 to cytosolic substrates has not yet been demonstrated clearly and hence its physiological function. In this study, we examined a potential role for Minpp1 in ER stress-induced apoptosis. We generated a custom antibody and characterized its specificity to study the expression of Minpp1 protein in multiple mammalian cells under experimentally induced cellular stress conditions. Our results demonstrate a significant increase in the expression of Minpp1 in response to a variety of cellular stress conditions. The protein expression was corroborated with the expression of its mRNA and enzymatic activity. Further, in an attempt to link the role of Minpp1 to apoptotic stress, we studied the effect of Minpp1 expression on apoptosis following silencing of the Minpp1 gene by its specific siRNA. Our results suggest an attenuation of apoptotic parameters following knockdown of Minpp1. Thus, in addition to its known role in inositol polyphosphate metabolism, we have identified a novel role for Minpp1 as a stress-responsive protein. In summary, our results provide, for the first time, a probable link between ER stress-induced apoptosis and Minpp1 expression.