The glycosaminoglycan, heparan sulfate (HS), binds proteins to modulate signaling events in embryogenesis. All identified protein-binding HS epitopes contain L-iduronic acid (IdoA). We report that targeted disruption of the murine D-glucuronyl C5-epimerase gene results in a structurally altered HS lacking IdoA. The corresponding phenotype is lethal, with renal agenesis, lung defects, and skeletal malformations. Unexpectedly, major organ systems, including the brain, liver, gastrointestinal tract, skin, and heart, appeared normal. We find that IdoA units are essential for normal kidney, lung, and skeletal development, albeit with different requirement for 2-Osulfation. By contrast, major early developmental events known to critically depend on heparan sulfate apparently proceed normally even in the absence of IdoA.

Amyloid diseases encompass >20 medical disorders that include amyloid protein A (AA) amyloidosis, Alzheimer's disease, and type 2 diabetes. A common feature of these conditions is the selective organ deposition of disease-specific fibrillar proteins, along with the sulfated glycosaminoglycan, heparan sulfate. We have generated transgenic mice that overexpress human heparanase and have tested their susceptibility to amyloid induction. Drastic shortening of heparan sulfate chains was observed in heparanaseoverproducing organs, such as liver and kidney. These sites selectively escaped amyloid deposition on experimental induction of inflammation-associated AA amyloidosis, as verified by lack of material staining with Congo Red, as well as lack of associated polysaccharide, whereas the same tissues from control animals were heavily infiltrated with amyloid. By contrast, the spleens of transgenic mice that failed to significantly overexpress heparanase contained heparan sulfate chains similar in size to those of control spleen and remained susceptible to amyloid deposition. Our findings provide direct in vivo evidence that heparan sulfate is essential for the development of amyloid disease.inflammation ͉ transgenic mice ͉ endo-glucuronidase ͉ Congo red staining

AR-23 is a melittin-related peptide with 23 residues. Like melittin, its high α-helical amphipathic structure results in strong bactericidal activity and cytotoxicity. In this study, a series of AR-23 analogues with low amphipathicity were designed by substitution of Ala1, Ala8 and Ile17 with positively charged residues (Arg or Lys) to study the effect of positively charged residue distribution on the biological viability of the antimicrobial peptide. Substitution of Ile17 on the nonpolar face with positively charged Lys dramatically altered the hydrophobicity, amphipathicity, helicity and the membrane-penetrating activity against human cells as well as the haemolytic activity of the peptide. However, substitution on the polar face only slightly affected the peptide biophysical properties and biological activity. The results indicate that the position rather than the number of positively charged residue affects the biophysical properties and selectivity of the peptide. Of all the analogues, A(A1R, A8R, I17K), a peptide with Ala1-Arg, Ala8-Arg and Ile17-Lys substitutions, exhibited similar bactericidal activity and anti-biofilm activity to AR-23 but had much lower haemolytic activity and cytotoxicity against mammalian cells compared with AR-23. Therefore, the findings reported here provide a rationalization for peptide design and optimization, which will be useful for the future development of antimicrobial agents.

Protein histidine phosphorylation in eukaryotes has been sparsely studied compared to protein serine/threonine and tyrosine phosphorylation. In an attempt to rectify this by probing porcine liver cytosol with the phosphohistidinecontaining peptide succinyl-Ala-His(P)-Pro-Phe-p-nitroanilide (phosphopeptide I), we observed a phosphatase activity that was insensitive towards okadaic acid and EDTA. This suggested the existence of a phosphohistidine phosphatase different from protein phosphatase 1, 2A and 2C. A 1000-fold purification to apparent homogeneity gave a 14-kDa phosphatase with a specific activity of 3 lmolAEmin )1 AEmg )1 at pH 7.5 with 7 lM phosphopeptide I as substrate. Partial amino-acid sequence determination of the purified porcine enzyme by MS revealed similarity with a human sequence representing a human chromosome 9 gene of hitherto unknown function. Molecular cloning from a human embryonic kidney cell cDNAlibrary followed by expression and purification, yielded a protein with a molecular mass of 13 700 Da, and an EDTA-insensitive phosphohistidine phosphatase activity of 9 lmolAEmin )1 AEmg )1 towards phosphopeptide I. No detectable activity was obtained towards a set of phosphoserine-, phosphothreonine-, and phosphotyrosine peptides. Northern blot analysis indicated that the human phosphohistidine phosphatase mRNA was present preferentially in heart and skeletal muscle. These results provide a new tool for studying eukaryotic histidine phosphorylation/dephosphorylation.Keywords: dephosphorylation; N-phosphorylation; phosphoamidase; phosphopeptide; protein histidine phosphatase.Boyer and coworkers detected protein-bound phosphohistidine in rat-liver mitochondrial succinyl-CoA synthetase almost 40 years ago [1,2]. Despite the long time interval and the fact that phosphohistidine represents a substantial fraction of eukaryotic protein-bound phosphate [3], only a few phosphohistidine-containing proteins have been detected compared to the large number of eukaryotic proteins phosphorylated on serine, threonine and tyrosine residues. One reason for this difference may be that the N-bound phosphate of phosphohistidine easily escapes detection by common analytical procedures, due to its lability under acidic conditions, e.g. during fixation and staining of gels after SDS/PAGE [4].The studies on eukaryotic protein histidine phosphorylation and dephosphorylation have dealt with essentially two aspects. One is the intermediary phosphorylation of enzymes [5][6][7][8][9][10], of which nucleoside diphosphate kinase is a particularly well-studied example. The other is the reversible protein histidine phosphorylation by protein kinases and phosphatases [3,11]. An important contribution to the latter field was the purification of a yeast protein histidine kinase in 1991 [12]. Access to this enzyme also made possible the preparation of 32 P-labelled histone H4, which was later used as substrate in the search for phosphohistidine phosphatases. Using such an approach, the catalytic subunits of the well-studied serine/...

Atherosclerosis, a chronic inflammatory disease, is the major cause of life-threatening complications such as myocardial infarction and stroke. Endothelial apoptosis plays a vital role in the initiation and progression of atherosclerotic lesions. Although a subset of microRNAs (miRs) have been identified as critical regulators of atherosclerosis, studies on their participation in endothelial apoptosis in atherosclerosis have been limited. In our study, we found that miR-26a expression was substantially reduced in the aortic intima of ApoE−/− mice fed with a high-fat diet (HFD). Treatment of human aortic endothelial cells (HAECs) with oxidized low-density lipoprotein (ox-LDL) suppressed miR-26a expression. Forced expression of miR-26a inhibited endothelial apoptosis as evidenced by MTT assay and TUNEL staining results. Further analysis identified TRPC6 as a target of miR-26a, and TRPC6 overexpression abolished the anti-apoptotic effect of miR-26a. Moreover, the cytosolic calcium and the mitochondrial apoptotic pathway were found to mediate the beneficial effects of miR-26a on endothelial apoptosis. Taken together, our study reveals a novel role of miR-26a in endothelial apoptosis and indicates a therapeutic potential of miR-26a for atherosclerosis associated with apoptotic cell death.