Overview: Recent Advances in Protein Kinase C Inhibitors

Glycolipids are important components of mammalian cell membranes and play an important role as signal mediators in cellular biology. Recently, the glycolipid mediated biological pathways have been drawing researchers’ attention. There has been a resurgence of interest in the signalling roles of glycolipid derivatives in the biochemical and biomedical research field. The design of glycolipid derivatives that block cell adhesion and regulate the immune response has highlighted potential therapeutic uses in the treatment of cancer, infection and other diseases originating in cell regulation disorder. This review summarises recent developments in the design of the four kinds of glycolipid related compounds (steroidal glycoside derivatives, glycosyl ceramide derivatives, glucosamine derivatives and glycero glycolipid derivatives) for therapeutic use.     

Immunocytochemical localization of GD3 ganglioside to astrocytes in murine cerebellar mutants

Biochemical analysis of the murine mutants, Purkinje cell degeneration (pcd/pcd), staggerer (sg/sg) and lurcher (Lc/+), which are characterized by neuronal degeneration in the cerebellar cortex, have revealed substantially elevated levels of GD3 ganglioside (ceramide-Glu-Gal-NANA-NANA). Ultrastructural studies on pcd/pcd and sg/sg have shown astrocytes elaborating slender sheet-like processes which wrap around neuronal processes. Seyfried et al. hypothesized that the elevation in GD3 seen in these mutants is attributed to its expression by altered astrocytes. Using a monoclonal antibody to GD3 and a polyclonal antibody to GFAP we have explored the cellular localization of GD3. Positive immunofluorescence was observed in sg/sg, pcd/pcd and Lc/+ cerebella, but not in age-matched normal littermates or in weaver (wv/wv) a fourth cerebellar murine mutation which destroys granule cells prior to their migration across the molecular layer. In wv/wv cerebella, astrocytes do not elaborate sheets of processes and no significant elevations of GD3 are observed biochemically. The positive GD3 staining in pcd/pcd and Lc/+ was confined to the granule cell layer and appeared as many punctate or short, fine profiles, suggestive of binding to thin cytoplasmic processes. No GD3 positive staining was seen in the Bergmann glia or astrocytes of the white matter. GD3-positive staining was seen throughout the cortex in sg/sg which displayed severe disruption of its histoarchitecture with no clear delineation between the molecular and granule cell layers. Ultrastructural localization of GD3 was performed using pre-embedding immunocytochemistry with a PAP technique in sg/sg mice. The cytoplasmic processes and cell bodies of astrocytes displayed positive membrane staining. Our results suggest that astrocytes undergo important changes in membrane composition during pathological reaction caused by neuronal degeneration.     

Evidence for disruption of sphingolipid metabolism in schizophrenia

As the field of glycobiology grows, important roles for glycolipids and glycoproteins in neurological disorders are being increasingly appreciated. However, few studies have explored the involvement of these molecules in the pathology of psychiatric illnesses. We investigated molecular differences related to glycobiology in subjects with schizophrenia by analyzing gene expression profiles using a focused glycogene chip, a custom-designed oligonucleotide array containing genes encoding proteins related to glycobiology, including glycosyltransferases, carbohydrate-binding proteins, proteoglycans, and adhesion molecules. We measured expression profiles in prefrontal cortical (BA46) samples from schizophrenic subjects and matched controls. We find differential expression of genes particularly related to glycosphingolipid/sphingolipid metabolism and N- and O-linked glycan biosynthesis in subjects with schizophrenia. Expression decreases of seven genes associated with these pathways, UGT8, SGPP1, GALC, B4GALT6, SPTLC2, ASAH1, and GAL3ST1, were validated by quantitative PCR in schizophrenic subjects with short-term illness. Only one of these genes, SPTLC2, showed differential expression in chronic schizophrenic subjects, although an increase in expression was observed. Covariate analysis showed that the expression of five of these genes was significantly positively correlated with age in schizophrenic, but not control, subjects. These changing patterns of expression could represent an adaptive response to pathology with disease progression or a compensatory effect of antipsychotic medication, although no significant correlations between gene expression levels and drug doses were observed. Disruption of sphingolipid metabolism early in illness could result in widespread downstream effects encompassing diverse pathological deficits already described in schizophrenia, especially those involving myelination and oligodendrocyte function; hence, this system may represent an important link in schizophrenia pathology.     

PapA1 and PapA2 are acyltransferases essential for the biosynthesis of the Mycobacterium tuberculosis virulence factor sulfolipid-1

Mycobacterium tuberculosis produces numerous exotic lipids that have been implicated as virulence determinants. One such glycolipid, Sulfolipid-1 (SL-1), consists of a trehalose-2-sulfate (T2S) core acylated with four lipid moieties. A diacylated intermediate in SL-1 biosynthesis, SL(1278), has been shown to activate the adaptive immune response in human patients. Although several proteins involved in SL-1 biosynthesis have been identified, the enzymes that acylate the T2S core to form SL(1278) and SL-1, and the biosynthetic order of these acylation reactions, are unknown. Here we demonstrate that PapA2 and PapA1 are responsible for the sequential acylation of T2S to form SL(1278) and are essential for SL-1 biosynthesis. In vitro, recombinant PapA2 converts T2S to 2'-palmitoyl T2S, and PapA1 further elaborates this newly identified SL-1 intermediate to an analog of SL(1278). Disruption of papA2 and papA1 in M. tuberculosis confirmed their essential role in SL-1 biosynthesis and their order of action. Finally, the Delta papA2 and Delta papA1 mutants were screened for virulence defects in a mouse model of infection. The loss of SL-1 (and SL(1278)) did not appear to affect bacterial replication or trafficking, suggesting that the functions of SL-1 are specific to human infection.     

加味逍遥颗粒联合二甲双胍对肥胖型多囊卵巢综合征的疗效观察

正多囊卵巢综合征(polycystic ovary syndrome,PCOS)是临床常见的内分泌和代谢紊乱性疾病,好发于肥胖群体,是引起育龄期妇女月经紊乱、无排卵性不孕的主要因素,其病理特征主要为高雄激素血症、胰岛素抵抗、糖脂代谢紊乱~[1]。长期排卵稀发或无排卵、高雄激素血症、月经异常等是其常见临床表现~[2]。目前PCOS患者多伴随肥胖或超重现象,机体存在高胰岛素水平,糖脂代谢紊乱和性激素水平失     

The crystal structure of avian CD1 reveals a smaller,more primordial antigen-binding pocket compared to mammalian CD1

The molecular details of glycolipid presentation by CD1 antigen-presenting molecules are well studied in mammalian systems. However, little is known about how these non-classical MHC class I (MHCI) molecules diverged from the MHC locus to create a more complex, hydrophobic binding groove that binds lipids rather than peptides. To address this fundamental question, we have determined the crystal structure of an avian CD1 (chCD1–2) that shares common ancestry with mammalian CD1 from ≈310 million years ago. The chCD1–2 antigen-binding site consists of a compact, narrow, central hydrophobic groove or pore rather than the more open, 2-pocket architecture observed in mammalian CD1s. Potential antigens then would be restricted in size to single-chain lipids or glycolipids. An endogenous ligand, possibly palmitic acid, serves to illuminate the mode and mechanism of ligand interaction with chCD1–2. The palmitate alkyl chain is inserted into the relatively shallow hydrophobic pore; its carboxyl group emerges at the receptor surface and is stabilized by electrostatic and hydrogen bond interactions with an arginine residue that is conserved in all known CD1 proteins. In addition, other novel features, such as an A′ loop that interrupts and segments the normally long, continuous α1 helix, are unique to chCD1–2 and contribute to the unusually narrow binding groove, thereby limiting its size. Because birds and mammals share a common ancestor, but the rate of evolution is slower in birds than in mammals, the chCD1–2-binding groove probably represents a more primordial CD1-binding groove.     

Immunopathogenesis and treatment of the guillain-barré syndrome—part I

The etiology of the Guillain-Barré syndrome (GBS) still remains elusive. Recent years have witnessed important advances in the delineation of the mechanisms that may operate to produce nerve damage. Evidence gathered from cell biology, immunology, and immunopathology studies in patients with GBS and animals with experimental autoimmune neuritis (EAN) indicate that GBS results from aberrant immune responses against components of peripheral nerve. Autoreactive T lymphocytes specific for the myelin antigens PO and P2 and circulating antibodies to these antigens and various glycoproteins and glycolipids have been indentified but their pathogenic role remains unclear. The multiplicity of these factors and the involvement of several antigen nonspecific proinflammatory mechanisms suggest that a complex interaction of immune pathways results in nerve damage. Data on disturbed humoral immunity with particular emphasis on glycolipid antibodies and on activation of autoreactive T lymphocytes and macrophages will be reviewed. Possible mechanisms underlying initiation of peripheral nerve-directed immune responses will be discussed with particular emphasis on the recently highlighted association with Campylobacter jejuni infection.© 1995 John Wiley &Sons, Inc.     

Antisera to different glycolipids induce myelin alterations in mouse spinal cord tissue cultures

To study the demyelinative effects of antibodies to glycolipids, well-myelinated cultures of mouse spinal cord tissue were exposed to antisera against galactocerebroside and two gangliosides (GM₁ and GM₄), as well as to anti-white matter antiserum. The demyelinative process was evaluated by morphologic and biochemical techniques. Cultures exposed to anti-white matter and anti-galactocerebroside antisera showed the most marked changes. These consisted of a decrease in the number of oligodendroglial cells and dissolution and phagocytosis of myelin. Concomitantly, the activity of 2′,3′-cyclic nucleotide-3′-phosphohydrolase (CNPase) was decreased by 60–70%. This occured within 24 h of exposure to a relatively low concentration of serum (10%). Cultures exposed to anit-GM₁ and anti-GM₄ antisera showed similar changes but to a lasser degree. The CNPase activity was decreased about 30% within 48 h of exposure to a 25% concentration of these antisera. This diminution represents about a 20% loss of myelin, an observation corroborated by electron microscopy where myelin but not oligodendroglial cell was observed. Therefore, in addition to anti-galactocerebroside activity, which was previously found to be the major antibody responsible for the demyelinating activity induced by anti-whole CNS tissue antiserum, these data suggest that antibodies to gangliosides like GM₁ and GM₄ might also play a role in immune-mediated demyelination, including perhaps, the human demyelinating diseases.     

Organization of oligodendroglial membrane sheets: II. Galactocerebroside:antibody interactions signal changes in cytoskeleton and myelin basic protein

Antibodies to galactocerebroside (GalC) cause patching of this surface glycolipid over internal domains of myelin basic protein (MBP), which are demarcated by a network of microtubules. The patching occurs whether or not second antibody is present, but the process is accelerated by the presence of second antibody. GalC patching results in disruption of microtubules in the lacy networks in oligodendroglial membrane sheets and in the eventual fusion of MBP domains, similar to the effects of colchicine (Dyer and Benjamins, 1989). Antibodies to GalC also disrupt F-actin in the lacy networks. Since colchicine does not alter the distribution of F-actin, anti-GalC is causing F-actin redistribution by a mechanism other than microtubule depolymerization. Extended exposure to anti-GalC results in coalescence of surface GalC patches concomitant with fusion of internal MBP domains. When anti-GalC is applied to induce GalC patching in cells previously treated with cytoskeletal inhibitors, patching is altered. After colchicine treatment, GalC surface staining is granular; i.e., patching is totally disorganized. Following cytochalasin B treatment, most membrane sheets display a few very large patches rather than the normal multiple, small patches. These GalC surface patterns are similar to the MBP distributions following the respective drug treatments (Dyer and Benjamins, 1989). Thus, the pattern of GalC distribution in the presence of antibody always reflects the organization of the underlying MBP domains; in turn, the organization of the MBP domains is determined by the lacy networks of microtubules in the oligodendroglial membrane sheets.