Inactivation of MAPK in epididymal fat and amelioration of triglyceride secretion by injection of GRK2 siRNA in ob/ob mice

Naunyn-Schmiedeberg's Archives of Pharmacology - Abnormal G protein-coupled receptor kinase 2 (GRK2) accumulation has a crucial role in the development of insulin resistance and diabetes....     

Effects of chlorhexidine, minocycline, and metronidazole on Porphyromonas gingivalis strain 381 in biofilms

BACKGROUND: Porphyromonas gingivalis is found in subgingival biofilm and is associated with periodontal disease. Bacteria in biofilms are able to resist higher antimicrobial concentrations than in suspension. Little is known about the susceptibility of P. gingivalis in biofilms to antimicrobial agents. The effects of chlorhexidine gluconate, minocycline hydrochloride, and metronidazole on P. gingivalis biofilms were examined in vitro. METHODS: P. gingivalis strain 381 biofilms were prepared on 32 hydroxyapatite disks. At 0, 24, 72, and 144 hours after perfusion of the three antimicrobial agents, two disks from each device were used to assess the antimicrobial effects by adenosine triphosphate (ATP) bioluminescence, and for morphological investigation by scanning electron microscopy (SEM). RESULTS: Close relationships were found between the results of the ATP analyses and the SEM observations in all groups examined. A significant decrease (P < 0.001) in ATP content was found between the chlorhexidine-treated and control groups. The extracellular matrix structure and P. gingivalis cells were altered in the presence of chlorhexidine. Minocycline hydrochloride also caused a decrease (P < 0.05) in the ATP content and morphological change on P. gingivalis biofilms. Metronidazole showed no significant efficacy against P. gingivalis biofilms. CONCLUSION: Chlorhexidine gluconate was effective at reducing the viability of P. gingivalis 381 cells in biofilms, while minocycline hydrochloride and metronidazole exhibited weaker effects.     

Correction to: Renal involvement of monoclonal immunoglobulin deposition disease associated with an unusual monoclonal immunoglobulin A glycan profile

Clinical and Experimental Nephrology -     

Phlebosclerotic colitis that was difficult to distinguish from collagenous colitis

Phlebosclerotic colitis is a rare and recently known disease entity and its etiology is still to be elucidated. Some phlebosclerotic colitis cases are difficult to distinguish from collagenous colitis because of the similarity of pathological findings. In all Japanese case reports of phlebosclerotic colitis in which an association with the use of Chinese herbal medicine is suspected, sansisi (gardenia fruit) was included, suggesting pathogenesis of this disease. We report a case of phlebosclerotic colitis that wasdifficult to be distinguished from collagenous colitis, and an association with the use of Chinese herbal medicine was suspected as the cause of the disease.     

Potent stimulation of myofilament force and adenosine triphosphatase activity of canine cardiac muscle through a direct enhancement of troponin C Ca++ binding by MCI-154, a novel cardiotonic agent

In the present study we have analyzed a likely biochemical mechanism underlying the Ca++-sensitizing action of MCI-154 (6-[4-(4'-pyridyl)aminophenyl)-4,5-dihydro-3(2H)-pyridazinone hydrochloride), a novel cardiotonic agent, on the contractile protein system. MCI-154 (10(-7) to 10(-4) M) enhanced the tension development induced by -log molar-free Ca++ concentration (pCa) 5.8 in chemically skinned fiber from the canine right ventricular muscle in a concentration-dependent manner. At pCa 7.0, MCI-154 (10(-7) to 10(-4) M) markedly increased adenosine triphosphatase (ATPase) activities of canine myofibrils and reconstituted actomyosin. In myofibrils and reconstituted actomyosin, MCI-154 (10(-7) to 10(-4) M) caused a parallel shift of the pCa-ATPase activity relation curve to the left without affecting the maximum activity, suggesting an increase in Ca++ sensitivity. MCI-154 (10(-8) to 10(-4) M) had little effect on actin-activated, Mg++, Ca++ and (K+, EDTA)-ATPase activities of myosin. Ca++ binding to cardiac myofibrils or purified cardiac troponin was increased by 10(-4) M MCI-154. These results suggest that MCI-154 enhances Ca++ binding to cardiac troponin C to elevate the Ca++ sensitivity of myofilaments and thus may cause a positive inotropic action in cardiac muscle. MCI-154 may provide a valuable tool for studying the molecular mechanism by which Ca++ regulates the contractile system.     

Gab family proteins are essential for postnatal maintenance of cardiac function via neuregulin-1/ErbB signaling

Grb2-associated binder (Gab) family of scaffolding adaptor proteins coordinate signaling cascades downstream of growth factor and cytokine receptors. In the heart, among EGF family members, neuregulin-1beta (NRG-1beta, a paracrine factor produced from endothelium) induced remarkable tyrosine phosphorylation of Gab1 and Gab2 via erythroblastic leukemia viral oncogene (ErbB) receptors. We examined the role of Gab family proteins in NRG-1beta/ErbB-mediated signal in the heart by creating cardiomyocyte-specific Gab1/Gab2 double knockout mice (DKO mice). Although DKO mice were viable, they exhibited marked ventricular dilatation and reduced contractility with aging. DKO mice showed high mortality after birth because of heart failure. In addition, we noticed remarkable endocardial fibroelastosis and increase of abnormally dilated vessels in the ventricles of DKO mice. NRG-1beta induced activation of both ERK and AKT in the hearts of control mice but not in those of DKO mice. Using DNA microarray analysis, we found that stimulation with NRG-1beta upregulated expression of an endothelium-stabilizing factor, angiopoietin 1, in the hearts of control mice but not in those of DKO mice, which accounted for the pathological abnormalities in the DKO hearts. Taken together, our observations indicated that in the NRG-1beta/ErbB signaling, Gab1 and Gab2 of the myocardium are essential for both maintenance of myocardial function and stabilization of cardiac capillary and endocardial endothelium in the postnatal heart.     

A heterozygous mutation of GALNTL5 affects male infertility with impairment of sperm motility

For normal fertilization in mammals, it is important that functionally mature sperm are motile and have a fully formed acrosome. The glycosyltransferase-like gene, human polypeptide N-acetylgalactosaminyltransferase-like protein 5 (GALNTL5), belongs to the polypeptide N-acetylgalactosamine-transferase (pp-GalNAc-T) gene family because of its conserved glycosyltransferase domains, but it uniquely truncates the C-terminal domain and is expressed exclusively in human testis. However, glycosyltransferase activity of the human GALNTL5 protein has not been identified by in vitro assay thus far. Using mouse Galntl5 ortholog, we have examined whether GALNTL5 is a functional molecule in spermatogenesis. It was observed that mouse GALNTL5 localizes in the cytoplasm of round spermatids in the region around the acrosome of elongating spermatids, and finally in the neck region of spermatozoa. We attempted to establish Galntl5-deficient mutant mice to investigate the role of Galntl5 in spermiogenesis and found that the heterozygous mutation affected male fertility due to immotile sperm, which is diagnosed as asthenozoospermia, an infertility syndrome in humans. Furthermore, the heterozygous mutation of Galntl5 attenuated glycolytic enzymes required for motility, disrupted protein loading into acrosomes, and caused aberrant localization of the ubiquitin–proteasome system. By comparing the protein compositions of sperm from infertile males, we found a deletion mutation of the exon of human GALNTL5 gene in a patient with asthenozoospermia. This strongly suggests that the genetic mutation of human GALNTL5 results in male infertility with the reduction of sperm motility and that GALNTL5 is a functional molecule essential for mammalian sperm formation.O-glycosylation begins by the addition of N-acetylgalactosamine to the serine or threonine residues in the target protein. This first step occurs in the Golgi apparatus, and is mediated by UDP-GalNAc: polypeptide N-acetylgalactosaminyltransferases (pp-GalNAc-T; EC 2.4.1.41), which transfer GalNAc from the nucleotide sugar to the acceptor residues (1). Polypeptide N-acetylgalactosaminyltransferase-like protein 5 [GALNTL5, also described as pp-GalNac-T19 (2) or GalNac-T20 (3); Refseq accession no.: {"type":"entrez-protein","attrs":{"text":"NP_660335.2","term_id":"281485547","term_text":"NP_660335.2"}}NP_660335.2] is classified as a member of the pp-GalNAc-T family because GALNTL5 possesses highly conserved catalytic domains of pp-GalNAc-T, whereas it uniquely lacks the conserved lectin domain at the C terminus. Thus far, 20 distinct pp-GalNAc-T genes have been identified in the human genome (2, 4–6). The in vitro enzymatic activities as a glycosyltransferase have been confirmed for 14 members of this family using acceptor peptide substrates (2, 7), but not identified for the other 6 members, including GALNTL5. During the preparation of this paper, it was reported that the transferase activity of GALNTL5 (GalNAc-T20) could not be detected using in vitro assays (3). The in vivo functions of these isoforms are poorly understood because of the absence of specific enzymatic activity. Meanwhile, O-fucosyltransferase 1, a member of a fucosyltransferase family, exhibits chaperon activity specific to Notch folding in Drosophila (8). One possibility is that the isoforms lacking enzymatic activities may have functions other than characteristics of glycosyltransferases, despite having typical glycosyltransferase motifs.Spermatogenesis is a complex process in which spermatogonial stem cells form spermatozoa through the proliferative phase (spermatogonia), the meiotic phase (spermatocytes), and the differentiation or spermiogenic phase (spermatids). Spermatids are connected by intercellular bridges, through which cytoplasmic constituents are shared among haploid spermatids (9). In the last spermiogenic phase, the round haploid spermatids differentiate into spermatozoa where acrosomes and tails unique and necessary for fertilization are developed. Spermatozoa are released through the seminiferous lumen into the epididymis, where they undergo further maturation and acquire motility. Sperm motility is an important factor in normal fertilization, whereas over 80% of sperm samples from infertile men demonstrate asthenozoospermia, poor sperm motility (10). Although defects of many potential genes are reported in mouse models exhibiting asthenozoospermia (11), it is rare that mutations in these genes are identified in human patients with asthenozoospermia.To investigate the biochemical machineries and biological functions of glycosylation, we performed comprehensive identification of the mammalian glycosyltransferase genes using various approaches and confirmed their enzymatic activity in vitro using biochemical methods (12). During these studies, we identified a unique isoform of the human GALNTL5 gene restricted to the human testis. However, we could not confirm the glycosyltransferase activity of GALNTL5, including whether it is a functional molecule in spermatogenesis. Therefore, using the mouse Galntl5 gene, we attempted to elucidate the biological role of GALNTL5 in spermatogenesis and found that the heterozygous mutation of Galntl5 causes male infertility by reducing sperm motility, which highly resembles human asthenozoospermia. In reference to the aberrant protein compositions of sperm from the Galntl5 heterozygous mutant mice (Ht mice), we found a patient with asthenozoospermia carrying one heterozygous nucleotide deletion at the sixth exon of the human GALNTL5 gene. Together with these data, we speculate that the function of GALNTL5 is indispensable for mature sperm formation and that GALNTL5 might have a unique role in mammalian spermiogenesis.     

Probing the binding specificities of human Siglecs by cell-based glycan arrays

Siglecs are a family of sialic acid–binding receptors expressed by cells of the immune system and a few other cell types capable of modulating immune cell functions upon recognition of sialoglycan ligands. While human Siglecs primarily bind to sialic acid residues on diverse types of glycoproteins and glycolipids that constitute the sialome, their fine binding specificities for elaborated complex glycan structures and the contribution of the glycoconjugate and protein context for recognition of sialoglycans at the cell surface are not fully elucidated. Here, we generated a library of isogenic human HEK293 cells with combinatorial loss/gain of individual sialyltransferase genes and the introduction of sulfotransferases for display of the human sialome and to dissect Siglec interactions in the natural context of glycoconjugates at the cell surface. We found that Siglec-4/7/15 all have distinct binding preferences for sialylated GalNAc-type O-glycans but exhibit selectivity for patterns of O-glycans as presented on distinct protein sequences. We discovered that the sulfotransferase CHST1 drives sialoglycan binding of Siglec-3/8/7/15 and that sulfation can impact the preferences for binding to O-glycan patterns. In particular, the branched Neu5Acα2–3(6-O-sulfo)Galβ1–4GlcNAc (6′-Su-SLacNAc) epitope was discovered as the binding epitope for Siglec-3 (CD33) implicated in late-onset Alzheimer’s disease. The cell-based display of the human sialome provides a versatile discovery platform that enables dissection of the genetic and biosynthetic basis for the Siglec glycan interactome and other sialic acid–binding proteins.

Immune cells are equipped with an array of glycan-binding proteins (GPBs) capable of interpreting the biological information encoded by glycans. Endogenous GBPs recognize host-derived “self” and foreign-derived “nonself” glycans and produce cues that are integrated into the signaling network of immune cells and contribute to immune homeostasis and the immune response (1). Siglecs (sialic acid–binding immunoglobulin-like lectins) serve in self-recognition and transmit immune inhibitory signals upon binding to a select repertoire of sialoglycans expressed by host cells raising the threshold for immune activation (2, 3). The human Siglec family consists of 14 functionally expressed members, and these are composed of an N-terminal V-set immunoglobulin (Ig)-like domain that mediates sialoglycan binding followed by varying numbers of C2-set Ig-like domains. Intracellularly, most Siglecs have immunoreceptor tyrosine-based inhibition motifs, and Siglec-14/15/16 carry immunoreceptor tyrosine-based activation motifs (3–7). Siglecs are broadly expressed throughout the immune system, and several Siglecs are also found outside of the immune system, such as Siglec-4 (MAG), which is expressed by oligodendrocytes and Schwann cells in the nervous system (8). Although the diverse biological functions within and outside of the immune system of Siglecs are not fully understood, Siglecs generally contribute to immune homeostasis by dampening immune activation upon recognition of sialoglycans. For example, Siglec-2 (CD22) can suppress B cell receptor activation (9), and Siglec-9 can dampen neutrophil activation (10). Cancer cells with aberrant sialoglycans and pathogens that express sialic acids can exploit Siglec signaling to modulate immune responses (11, 12). Moreover, Siglec-3 (CD33) is strongly associated with risk for Alzheimer’s disease and expressed on microglia cells (13, 14). Given the potent immune modulatory functions of Siglecs and their wide involvement in autoimmunity, infection, cancer, and neurodegeneration, Siglecs are promising therapeutic targets (7, 15). However, many of the natural ligands of Siglecs have not been fully identified, and endogenous ligands for several Siglecs including Siglec-3/CD33 remain elusive.Human cells can produce a large diversity of glycans capped with sialic acids (Sia), a family of chemically diverse sugars with N-acetylneuraminic acid (Neu5Ac) being the predominant type in humans. Sialic acids are generally found at the termini of mammalian glycans, and most types of glycoconjugates including N-glycoproteins, multiple types of O-glycoproteins, and glycolipids carry oligosaccharides capped by sialic acids (16, 17). Sialylation is one of the most complex regulated steps in glycosylation with 20 distinct Golgi-located sialyltransferase isoenzymes dedicated to catalyze transfer of sialic acids to galactose (ST3GAL1-6, ST6GAL1 and 2), N-Acetylgalactosamine (Gal-NAc) (ST6GALNAC1-6), or sialic acid (ST8SIA1-6) via α2-3, α2-6, or α2-8 linkages, respectively and with different preferences for the underlying glycan structures and types of glycoconjugate (18–20). The resulting plethora of sialic acid-containing glycans constituting the sialome of cells provides a vast catalog of ligands for Siglecs and potential for distinct instructive cues for the immune response (16). The current insight into the interactome of Siglecs is largely derived from studies with libraries of synthetic and natural glycans printed on glass arrays (21, 22). These glycan arrays have demonstrated distinct structural glycan features that drive selective binding of individual Siglecs, including the linkage type of sialic acids, the core disaccharide carrying sialic acids, and glycan modifications such as sulfation or acetylation (23–27). However, printed glycan arrays may not present glycans in the natural context of the overall glycoconjugate structure and the cell surface with spatial organization and competition dynamics limiting insight into the fine binding specificities of Siglecs and their interactions with the host cell sialome.Here, we took advantage of our recently developed cell-based glycan array strategy (28–30) and generated an expanded sialome sublibrary with the human embryonic kidney (HEK) 293 for dissection of Siglec binding properties. First, combinatorial gene knockout (KO) was used to delete distinct subsets of sialyltransferase isoenzymes or all endogenous sialylation capacity. Second, using targeted gene knock-in (KI), individual sialyltransferase isoenzymes were introduced in the absence of other isoenzymes. Finally, we introduced selected sulfotransferase isoenzymes to explore cross-talk between sialylation and sulfation. To specifically address the influence of clustered O-glycan presentation for Siglec binding, we introduced a large panel of reporter constructs designed to display human O-glycodomains derived from mucins and mucin-like O-glycoproteins with different densities and patterns of O-glycans. The cell-based sialome array reproduced previous results for binding specificities for Siglec-2 (CD22) and Siglec-9 and led to insight into the binding specificities of Siglec-4/7/15 for distinct GalNAc-type O-glycans and their presentation on O-mucin–like glycoproteins. Finally, we demonstrate that Siglec-3/7/8/15 have preferential binding to sulfated sialoglycans yet have different specificities for underlying glycoconjugate structures. We further discovered the 6′-Su-SLacNAc (Neu5Acα2-3[6-O-sulfo]Galβ1-4GlcNAc) epitope on N-glycans and glycolipids as the ligand for Siglec-3/CD33 as well as Siglec-8. In summary, the cell-based display of the human sialome enables dissection of the Siglec interactome in the natural context of a human cell and provides the biosynthetic and genetic basis for the identified ligands.