Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.3.1 (alkaline phosphatase)
47,916 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Familial hypophosphataemic rickets (XLH) is an X-linked dominant disorder resulting in hypophosphataemia, abnormal regulation of 25-hydroxy vitamin D metabolism, elevated activity of alkaline phosphatase, bone deformities and short stature. In 1995-97 the sequence of PEX gene responsible for the disease was established. The PEX gene spreads 24.3 kb and includes 22 small exons coding a protein belonging to a neutral endopeptidase family. Function of the protein is not known yet. Mutation analysis in patients from North America, Africa and Europe (including Poland) revealed the presence of many different types of the PEX gene mutations. Identified deletions, insertions and substitution are supposed to change the structure of the PEX protein. Active form of vitamin D3, 1-alpha-hydroxylase and phosphate supplementation are now the recommended treatment of XLH patients. Further research is necessary to understand the role of the PEX protein in the pathogenesis of hypophosphatamic rickets.
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PMID:[Molecular aspects of familial hypophosphatemic rickets]. 1091 Jun 42

The genes responsible for X-linked hypophosphatemic (XLH) vitamin D-resistant rickets and the murine homolog, hypophosphatemic mice (Hyp), were identified as PHEX and Phex (phosphate-regulating gene with homology to endopeptidases on the X chromosome), respectively. However, the mechanism by which inactivating mutations of PHEX cause XLH remains unknown. We investigated the mechanisms by syngeneic bone marrow transplantation (BMT) from wild mice to Hyp mice. The expression of the Phex gene was detected in mouse BM cells. BMT introduced a chimerism in recipient Hyp mice and a significant increase in the serum phosphorus level. The renal sodium phosphate cotransporter gene expression was significantly increased. The effect of BMT on the serum phosphorus level depended on engraftment efficiencies, which represent the dosage of normal gene. Similarly, the serum alkaline phosphatase (ALP) activity was decreased and bone mineral density was increased. Furthermore, the renal expression of 25-hydroxyvitamin D3 24-hydroxylase, which is a key enzyme in the catabolic pathway and is increased in XLH/Hyp, was improved. From these results, we conclude that transplantation of normal BM cells improved abnormal bone mineral metabolism and deranged vitamin D metabolism in Hyp by replacing defective gene product(s) with normal gene product(s). This result may provide strong evidence for clinical application of BMT in metabolic bone disorders.
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PMID:The effects of bone marrow transplantation on X-linked hypophosphatemic mice. 1093 43

Full-length cDNA coding for dentin matrix protein 1 (DMP1) has been cloned and sequenced, but the corresponding complete protein has not been isolated. In searching for naturally occurring DMP1, we recently discovered that the extracellular matrix of bone contains fragments originating from DMP1. Shortened forms of DMP1, termed 37K and 57K fragments, were treated with alkaline phosphatase and then digested with trypsin. The resultant peptides were purified by a two-dimensional method: size exclusion followed by reversed-phase high performance liquid chromatography. Purified peptides were sequenced by Edman degradation and mass spectrometry, and the sequences compared with the DMP1 sequence predicted from cDNA. Extensive sequencing of tryptic peptides revealed that the 37K fragments originated from the NH2-terminal region, and the 57K fragments were from the COOH-terminal part of DMP1. Phosphate analysis indicated that the 37K fragments contained 12 phosphates, and the 57K fragments had 41. From 37K fragments, two peptides lacked a COOH-terminal lysine or arginine; instead they ended at Phe173 and Ser180 and were thus COOH termini of 37K fragments. Two peptides were from the NH2 termini of 57K fragments, starting at Asp218 and Asp222. These findings indicated that DMP1 is proteolytically cleaved at four bonds, Phe173-Asp174, Ser180-Asp181, Ser217-Asp218, and Gln221-Asp222, forming eight fragments. The uniformity of cleavages at the NH2-terminal peptide bonds of aspartyl residues suggests that a single proteinase is involved. Based on its reported specificity, we hypothesize that these scissions are catalyzed by PHEX protein. We envision that the proteolytic processing of DMP1 plays a crucial role during osteogenesis and dentinogenesis.
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PMID:Evidence for the proteolytic processing of dentin matrix protein 1. Identification and characterization of processed fragments and cleavage sites. 1281 42

The osteocyte is the most abundant cell type in bone and is embedded in mineralized bone matrix. Osteocytes are still poorly characterized because of their location and the lack of primary osteocyte isolation methods. Data on the cell biology of osteocytes is especially limited. We have isolated primary osteocytes from rat cortical bone by applying repeated enzymatic digestion and decalcification. The isolated osteocytes expressed typical osteocytic morphology with cell-cell contacts via long protrusions after a 1-day culture. These cells were negative or faintly positive for alkaline phosphatase but expressed high levels of osteocalcin, PHEX (phosphate-regulating gene with homology to endopeptidases on the X chromosome), and DMP1 (dentin matrix protein 1). These cells also revealed patchy membrane staining for connexin43. For studying the function of gap junctions in isolated osteocytes, we microinjected rhodamine-labeled dextran (MW: 10,000) and Lucifer yellow (MW: 457) and found that Lucifer yellow was rapidly transmitted to several surrounding cells, whereas dextran remained in the injected cells. Heptanol and 18alpha-glycyrrhetinic acid inhibited the transfer of Lucifer yellow. This clearly showed the existence of functional gap junctions in cultured osteocytes. Enveloped viruses, such as vesicular stomatitis virus and influenza A virus, were used for studying cell polarity. We were unable to demonstrate plasma membrane polarization with enveloped viruses in isolated primary osteocytes in culture. Our results suggest that osteocytes do not possess apical and basolateral plasma membrane domains as do osteoblasts, which are their precursors.
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PMID:Isolated primary osteocytes express functional gap junctions in vitro. 1617 87

We studied the effects of phosphates on the expression of the human tissue-nonspecific alkaline phosphatase (TNSALP) gene and phosphate-regulating genes in short-term cultures of human osteoblastic osteosarcoma cell lines. When human osteosarcoma cell lines, SaOS-2, MG-63, and U(2)OS were cultured with 10 mM inorganic sodium dihydrogenphosphate, 10 mM beta-glycerophosphate, 250 microM pyridoxal phosphate, or 100 microM inorganic pyrophosphate, enzymatic activity of alkaline phosphatase began to increase at 72 h after addition of sodium dihydrogenphosphate and beta-glycerophosphate in SaOS-2 cells. Pyridoxal phosphate and pyrophosphate did not induce alkaline phosphatase activity. U(2)OS cells slightly reacted to beta-glycerophosphate, but MG-63 cells did not react on exposure to phosphates. In SaOS-2 cells, TNSALP mRNA measured by real-time RT-PCR reached a peak level at 72 h after the addition of beta-glycerophosphate. PHEX and MEPE mRNAs were also induced by beta-glycerophosphate. These results suggest that TNSALP, PHEX and MEPE were concordantly induced by beta-glycerophosphate on mineralisation.
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PMID:Effects of phosphates on the expression of tissue-nonspecific alkaline phosphatase gene and phosphate-regulating genes in short-term cultures of human osteosarcoma cell lines. 1631 17

Cell-based therapies are used to treat bone defects. We recently described that human multipotent adipose-derived stem (hMADS) cells, which exhibit a normal karyotype, self renewal, and the maintenance of their differentiation properties, are able to differentiate into different lineages. Herein, we show that hMADS cells can differentiate into osteocyte-like cells. In the presence of a low amount of serum and EGF, hMADS cells express specific molecular markers, among which alkaline phosphatase, CBFA-1, osteocalcin, DMP1, PHEX, and podoplanin and develop functional gap-junctions. When loaded on a hardening injectable bone substitute (HIBS) biomaterial and injected subcutaneously into nude mice, hMADS cells develop mineralized woven bone 4 weeks after implantation. Thus hMADS cells represent a valuable tool for pharmacological and biological studies of osteoblast differentiation in vitro and bone development in vivo.
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PMID:Human adipose tissue-derived multipotent stem cells differentiate in vitro and in vivo into osteocyte-like cells. 1765 96

Most patients with inherited hypophosphatemic Rickets/Osteomalacia have mutations in the PHEX gene. In this brief review, we focus on the treatment for patients with this mutation. First, molecular basis of inherited hypophosphatemic Rickets/Osteomalacia, followed by pathophysiology of PHEX and its related disorders is described. Next, clinical manifestation of patients with PHEX mutations and the principles of the treatment are explained. Finally, a case with this mutation that has been long followed up is presented. The most common treatment for this disorder is administration of phosphate and vitamin D, both internationally and in Japan. Degree of the increment in serum inorganic phosphorus levels one hour after phosphate administration, in addition to a decrease in alkaline phosphatase levels is valuable in the monitoring of the treatment. During childhood, markers in a longer term, namely, improvement of X-ray findings and that of height velocity are also useful.
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PMID:[Hypophosphatemic rickets/osteomalacia. - Mainly on patients with PHEX mutations -]. 1790 14

Tissue-nonspecific alkaline phosphatase (TNAP) plays a key role in mineralization. A defect in the TNAP gene causes hypophosphatasia, which is characteristic of systemic skeletal hypomineralization. To determine the mineralizing ability of the mutant proteins, we developed a functional assay that uses U2OS osteoblast-like cells. Expression plasmids containing TNAP mutant cDNAs were constructed and introduced into U2OS cells, which are derived from a human osteosarcoma and exhibit very low alkaline phosphatase (ALP) activity and disabled mineralization. U2OS cells, in which active TNAP cDNAs were introduced, expressed high ALP activity and mineralized their circumstance when they were cultured with beta-glycerophosphate. The ALP activity in these U2OS cells corresponded to the activity reported for COS cells in which active TNAP cDNA was introduced. An in vitro mineralization assay of U2OS cells transfected with moderate allele cDNAs showed that approximately 35% of TNAP enzymatic activity may be the threshold value for mineralization. In addition, U2OS cells transfected with wild-type TNAP and polymorphism TNAP cDNA showed PHEX (phosphate-regulating gene with homologies to endopeptidases on the X chromosome) induction as in SaOS-2 cells. In summary, the introduction of active TNAP cDNA into U2OS cells allowed these cells to mineralize, and this technique may be a useful functional assay of TNAP mutant proteins.
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PMID:Functional assay of the mutant tissue-nonspecific alkaline phosphatase gene using U2OS osteoblast-like cells. 1845 59

Tissue-nonspecific alkaline phosphatase (TNAP) plays a key role in mineralization by degrading inorganic pyrophosphate and providing free inorganic phosphate. We have previously reported that TNAP is induced by beta-glycerophosphate and NaH(2)PO(4) in short-term cultures of SaOS-2 human osteoblast-like cells and that PHEX (phosphate-regulating gene with homologies to endopeptidase on the X chromosome) mRNA is also induced after TNAP induction. In the present study, we have investigated the effects of levamisole, a TNAP inhibitor, and phosphonoformic acid (PFA), a type III sodium-phosphate cotransporter inhibitor, on the phosphate-induced expression of TNAP and mineralization. Levamisole inhibited beta-glycerophosphate-induced mineralization, TNAP and PHEX expression, and the increase in enzymatic activity of NPP1 (5'-nucleotide pyrophosphatase phosphodiesterase 1), but did not inhibit NaH(2)PO(4)-induced mineralization. PFA completely inhibited NaH(2)PO(4)-induced mineralization and NPP1 enzymatic activation, and partly inhibited beta-glycerophosphate-induced mineralization, but did not affect the increase in TNAP activity. These results suggest that phosphate derived from TNAP-induced hydrolysis of beta-glycerophosphate yields signals that induce TNAP expression and mineralization, and that PHEX expression may be linked to TNAP expression. However, luciferase assays failed to detect any transcriptional activation of the promoter region of the human TNAP gene by beta-glycerophosphate or NaH(2)PO(4), suggesting that the effects of these phosphates may be indirect.
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PMID:The role of tissue-nonspecific alkaline phosphatase in the phosphate-induced activation of alkaline phosphatase and mineralization in SaOS-2 human osteoblast-like cells. 1850 Jun 57

Hypophosphatemia is an X-linked dominant disorder resulting from a mutation in the PHEX gene. While osteoblast-specific expression of the PHEX transgene has been reported to decrease the phosphate wasting associated with the disease in male hypophosphatemic (HYP) mice, there are reports that the mineralization defect is only partially corrected in young animals. To test the hypothesis that osteoblast-specific expression of the PHEX gene for a longer time would correct the mineralization defect, this study examined the bones of 9-month-old male and female HYP mice and their wild-type controls with or without expression of the transgene under a collagen type I promoter. Serum phosphate levels, alkaline phosphatase activity, and FGF23 levels were also measured. Mineral analyses based on wide-angle X-ray diffraction, Fourier transform-infrared (FT-IR) spectroscopy, and FT-IR imaging confirmed the decreased mineral content and increased mineral crystal size in male HYP humerii compared to wild-type males and females with or without the transgene and in female HYP mice with or without the transgene. There was a significant increase in mineral content and a decrease in crystallinity in the HYP males' bones with the transgene, compared to those without. Of interest, expression of the transgene in wild-type animals significantly increased the mineral content in both males and females without having a detectable effect on crystallinity or carbonate content. In contrast to the bones, based on micro-computed tomography and FT-IR imaging, at 9 months there were no significant differences between the HYP and the WT teeth, precluding analysis of the effect of the transgene.
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PMID:The PHEX transgene corrects mineralization defects in 9-month-old hypophosphatemic mice. 1908 53


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