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Blood Oct 2014Paroxysmal nocturnal hemoglobinuria (PNH) is a rare bone marrow failure disorder that manifests with hemolytic anemia, thrombosis, and peripheral blood cytopenias. The... (Review)
Review
Paroxysmal nocturnal hemoglobinuria (PNH) is a rare bone marrow failure disorder that manifests with hemolytic anemia, thrombosis, and peripheral blood cytopenias. The absence of two glycosylphosphatidylinositol (GPI)-anchored proteins, CD55 and CD59, leads to uncontrolled complement activation that accounts for hemolysis and other PNH manifestations. GPI anchor protein deficiency is almost always due to somatic mutations in phosphatidylinositol glycan class A (PIGA), a gene involved in the first step of GPI anchor biosynthesis; however, alternative mutations that cause PNH have recently been discovered. In addition, hypomorphic germ-line PIGA mutations that do not cause PNH have been shown to be responsible for a condition known as multiple congenital anomalies-hypotonia-seizures syndrome 2. Eculizumab, a first-in-class monoclonal antibody that inhibits terminal complement, is the treatment of choice for patients with severe manifestations of PNH. Bone marrow transplantation remains the only cure for PNH but should be reserved for patients with suboptimal response to eculizumab.
Topics: Bone Marrow Transplantation; Glycosylphosphatidylinositols; Hemoglobinuria, Paroxysmal; Humans; Monitoring, Physiologic; Mutation
PubMed: 25237200
DOI: 10.1182/blood-2014-02-522128 -
Medicina (Kaunas, Lithuania) Sep 2023Paroxysmal nocturnal hemoglobinuria (PNH) is a nonmalignant clonal hematopoietic disorder characterized by the lack of glycosylphosphatidylinositol-anchored proteins... (Review)
Review
Paroxysmal nocturnal hemoglobinuria (PNH) is a nonmalignant clonal hematopoietic disorder characterized by the lack of glycosylphosphatidylinositol-anchored proteins (GPI-APs) as a consequence of somatic mutations in the phosphatidylinositol glycan anchor biosynthesis class A () gene. Clinical manifestations of PNH are intravascular hemolysis, thrombophilia, and bone marrow failure. Treatment of PNH mainly relies on the use of complement-targeted therapy (C5 inhibitors), with the newest agents being explored against other factors involved in the complement cascade to alleviate unresolved intravascular hemolysis and extravascular hemolysis. This review summarizes the biology and current treatment strategies for PNH with the aim of reaching a general audience with an interest in hematologic disorders.
Topics: Humans; Hemoglobinuria, Paroxysmal; Hemolysis; Complement System Proteins; Thrombophilia; Glycosylphosphatidylinositols; Biology
PubMed: 37763731
DOI: 10.3390/medicina59091612 -
Frontiers in Immunology 2021Paroxysmal Nocturnal Hemoglobinuria (PNH) is a disease as simple as it is complex. PNH patients develop somatic loss-of-function mutations in phosphatidylinositol... (Review)
Review
Paroxysmal Nocturnal Hemoglobinuria (PNH) is a disease as simple as it is complex. PNH patients develop somatic loss-of-function mutations in phosphatidylinositol -acetylglucosaminyltransferase subunit A gene (), required for the biosynthesis of glycosylphosphatidylinositol (GPI) anchors. Ubiquitous in eukaryotes, GPI anchors are a group of conserved glycolipid molecules responsible for attaching nearly 150 distinct proteins to the surface of cell membranes. The loss of two GPI-anchored surface proteins, CD55 and CD59, from red blood cells causes unregulated complement activation and hemolysis in classical PNH disease. In PNH patients, -mutant, GPI (-) hematopoietic cells clonally expand to make up a large portion of patients' blood production, yet mechanisms leading to clonal expansion of GPI (-) cells remain enigmatic. Historical models of PNH in mice and the more recent PNH model in rhesus macaques showed that GPI (-) cells reconstitute near-normal hematopoiesis but have no intrinsic growth advantage and do not clonally expand over time. Landmark studies identified several potential mechanisms which can promote PNH clonal expansion. However, to what extent these contribute to PNH cell selection in patients continues to be a matter of active debate. Recent advancements in disease models and immunologic technologies, together with the growing understanding of autoimmune marrow failure, offer new opportunities to evaluate the mechanisms of clonal expansion in PNH. Here, we critically review published data on PNH cell biology and clonal expansion and highlight limitations and opportunities to further our understanding of the emergence of PNH clones.
Topics: Animals; Autoimmunity; Biomarkers; Clonal Evolution; Cytokines; Disease Management; Disease Models, Animal; Disease Susceptibility; Genetic Predisposition to Disease; Glycosylphosphatidylinositols; Hematopoiesis; Hemoglobinuria, Paroxysmal; Humans; Lymphocyte Subsets; Mutation
PubMed: 35154088
DOI: 10.3389/fimmu.2021.830172 -
Chembiochem : a European Journal of... Jul 2023Glycosphingolipid (GSL) and glycosylphosphatidylinositol (GPI) are the two major glycolipids expressed by eukaryotic cells, and their metabolisms share the same... (Review)
Review
Glycosphingolipid (GSL) and glycosylphosphatidylinositol (GPI) are the two major glycolipids expressed by eukaryotic cells, and their metabolisms share the same machineries. Moreover, both GSLs and GPI-anchored proteins (GPI-APs) are localized in the cholesterol-rich regions, namely the lipid rafts, of the cell membrane, where many other signaling molecules are compartmentalized as well. Therefore, the interaction between GSLs and GPI-APs and their interactions with other molecules in the lipid rafts are inevitable. This review is focused on the influences of GSLs and GPI-APs on each other's biosynthesis, trafficking, cell membrane distribution, and biological functions, such as signal transduction.
Topics: Glycosphingolipids; Glycosylphosphatidylinositols; Cell Membrane; Proteins; Membrane Microdomains
PubMed: 36935354
DOI: 10.1002/cbic.202200761 -
Proceedings of the Japan Academy.... 2014At least 150 different human proteins are anchored to the outer leaflet of the plasma membrane via glycosylphosphatidylinositol (GPI). GPI preassembled in the... (Review)
Review
At least 150 different human proteins are anchored to the outer leaflet of the plasma membrane via glycosylphosphatidylinositol (GPI). GPI preassembled in the endoplasmic reticulum is attached to the protein's carboxyl-terminus as a post-translational modification by GPI transamidase. Twenty-two PIG (for Phosphatidyl Inositol Glycan) genes are involved in the biosynthesis and protein-attachment of GPI. After attachment to proteins, both lipid and glycan moieties of GPI are structurally remodeled in the endoplasmic reticulum and Golgi apparatus. Four PGAP (for Post GPI Attachment to Proteins) genes are involved in the remodeling of GPI. GPI-anchor deficiencies caused by somatic and germline mutations in the PIG and PGAP genes have been found and characterized. The characteristics of the 26 PIG and PGAP genes and the GPI deficiencies caused by mutations in these genes are reviewed.
Topics: Animals; Germ-Line Mutation; Glycosylphosphatidylinositols; Humans
PubMed: 24727937
DOI: 10.2183/pjab.90.130 -
Biological Chemistry Nov 2020Selective adhesion of fungal cells to one another and to foreign surfaces is fundamental for the development of multicellular growth forms and the successful... (Review)
Review
Selective adhesion of fungal cells to one another and to foreign surfaces is fundamental for the development of multicellular growth forms and the successful colonization of substrates and host organisms. Accordingly, fungi possess diverse cell wall-associated adhesins, mostly large glycoproteins, which present N-terminal adhesion domains at the cell surface for ligand recognition and binding. In order to function as robust adhesins, these glycoproteins must be covalently linkedto the cell wall via C-terminal glycosylphosphatidylinositol (GPI) anchors by transglycosylation. In this review, we summarize the current knowledge on the structural and functional diversity of so far characterized protein families of adhesion domains and set it into a broad context by an in-depth bioinformatics analysis using sequence similarity networks. In addition, we discuss possible mechanisms for the membrane-to-cell wall transfer of fungal adhesins by membrane-anchored Dfg5 transglycosidases.
Topics: Cell Adhesion; Glycosylphosphatidylinositols; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins
PubMed: 33035180
DOI: 10.1515/hsz-2020-0199 -
Biochimica Et Biophysica Acta Apr 2016Glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs) are a class of membrane proteins containing a soluble protein attached by a conserved glycolipid anchor to... (Review)
Review
Glycosylphosphatidylinositol (GPI)-anchored proteins (GPI-APs) are a class of membrane proteins containing a soluble protein attached by a conserved glycolipid anchor to the external leaflet of the plasma membrane. In polarized epithelial cells, GPI-APs are predominantly sorted to the apical surface in the trans-Golgi network (TGN) by clustering in sphingolipid- and cholesterol-dependent microdomains (or rafts), which have been proposed to act as apical sorting platforms. Recent data indicate that the mechanisms of GPI-AP sorting, occurring in the Golgi, control both the membrane transport of GPI-APs and their specific activity at the apical surface of fully polarized epithelial cells. Here, we discuss the most recent findings and the factors regulating apical sorting of GPI-APs at the Golgi in polarized epithelial cells. We also underline the differences in the plasma membrane organization of GPI-APs between polarized and non-polarized cells supporting the existence of various mechanisms that control GPI-AP organization in different cell types.
Topics: Cell Membrane; Cell Polarity; Cholesterol; Epithelial Cells; Glycosylphosphatidylinositols; Humans; Membrane Microdomains; Membrane Proteins; Protein Transport; trans-Golgi Network
PubMed: 26706096
DOI: 10.1016/j.bbamem.2015.12.018 -
Nature Communications May 2022Eukaryotic cells are coated with an abundance of glycosylphosphatidylinositol anchor proteins (GPI-APs) that play crucial roles in fertilization, neurogenesis, and...
Eukaryotic cells are coated with an abundance of glycosylphosphatidylinositol anchor proteins (GPI-APs) that play crucial roles in fertilization, neurogenesis, and immunity. The removal of a hydrophobic signal peptide and covalent attachment of GPI at the new carboxyl terminus are catalyzed by an endoplasmic reticulum membrane GPI transamidase complex (GPI-T) conserved among all eukaryotes. Here, we report the cryo-electron microscopy (cryo-EM) structure of the human GPI-T at a global 2.53-Å resolution, revealing an equimolar heteropentameric assembly. Structure-based mutagenesis suggests a legumain-like mechanism for the recognition and cleavage of proprotein substrates, and an endogenous GPI in the structure defines a composite cavity for the lipid substrate. This elongated active site, stemming from the membrane and spanning an additional ~22-Å space toward the catalytic dyad, is structurally suited for both substrates which feature an amphipathic pattern that matches this geometry. Our work presents an important step towards the mechanistic understanding of GPI-AP biosynthesis.
Topics: Cryoelectron Microscopy; Endoplasmic Reticulum; Glycosylphosphatidylinositols; Humans; Protein Sorting Signals; Proteins
PubMed: 35551457
DOI: 10.1038/s41467-022-30250-6 -
Journal of Diabetes Investigation Oct 2023In diabetes, the impairment of insulin secretion and insulin resistance contribute to hypertriglyceridemia, as the enzymatic activity of lipoprotein lipase (LPL) depends... (Review)
Review
In diabetes, the impairment of insulin secretion and insulin resistance contribute to hypertriglyceridemia, as the enzymatic activity of lipoprotein lipase (LPL) depends on insulin action. The transport of LPL to endothelial cells and its enzymatic activity are maintained by the formation of lipolytic complex depending on the multiple positive (glycosylphosphatidylinositol-anchored high-density lipoprotein binding protein 1 [GPIHBP1], apolipoprotein C-II [APOC2], APOA5, heparan sulfate proteoglycan [HSPG], lipase maturation factor 1 [LFM1] and sel-1 suppressor of lin-12-like [SEL1L]) and negative regulators (APOC1, APOC3, angiopoietin-like proteins [ANGPTL]3, ANGPTL4 and ANGPTL8). Among the regulators, GPIHBP1 is a crucial molecule for the translocation of LPL from parenchymal cells to the luminal surface of capillary endothelial cells, and maintenance of lipolytic activity; that is, hydrolyzation of triglyceride into free fatty acids and monoglyceride, and conversion from chylomicron to chylomicron remnant in the exogenous pathway and from very low-density lipoprotein to low-density lipoprotein in the endogenous pathway. The null mutation of GPIHBP1 causes severe hypertriglyceridemia and pancreatitis, and GPIGBP1 autoantibody syndrome also causes severe hypertriglyceridemia and recurrent episodes of acute pancreatitis. In patients with type 2 diabetes, the elevated serum triglyceride levels negatively correlate with circulating LPL levels, and positively with circulating APOC1, APOC3, ANGPTL3, ANGPTL4 and ANGPTL8 levels. In contrast, circulating GPIHBP1 levels are not altered in type 2 diabetes patients with higher serum triglyceride levels, whereas they are elevated in type 2 diabetes patients with diabetic retinopathy and nephropathy. The circulating regulators of lipolytic complex might be new biomarkers for lipid and glucose metabolism, and diabetic vascular complications.
Topics: Humans; Glycosylphosphatidylinositols; Diabetes Mellitus, Type 2; Endothelial Cells; Acute Disease; Pancreatitis; Hypertriglyceridemia; Carrier Proteins; Triglycerides; Lipoproteins, LDL; Lipoproteins, HDL; Angiopoietin-Like Protein 3; Proteins
PubMed: 37448184
DOI: 10.1111/jdi.14056 -
FEBS Letters Apr 2022Wnt signalling pathways play pivotal roles in development, homeostasis and human diseases, and are tightly regulated. We previously identified Tiki as a novel family of...
Wnt signalling pathways play pivotal roles in development, homeostasis and human diseases, and are tightly regulated. We previously identified Tiki as a novel family of Wnt inhibitory proteases. Tiki proteins were predicted as type I transmembrane proteins and can act in both Wnt-producing and Wnt-responsive cells. Here, we characterize Tiki proteins as glycosylphosphatidylinositol (GPI)-anchored proteases. TIKI1/2 proteins are enriched on the detergent-resistant membrane microdomains and can be released from the plasma membrane by GPI-specific glycerophosphodiesterases GDE3 and GDE6, but not by GDE2. The GPI anchor determines the cellular localization of Tiki proteins and their regulation by GDEs, but not their inhibitory activity on Wnt signalling. Our study uncovered novel characteristics and potential regulations of the Tiki family proteases.
Topics: Endopeptidases; Glycosylphosphatidylinositols; Humans; Membrane Proteins; Peptide Hydrolases; Signal Transduction
PubMed: 35182431
DOI: 10.1002/1873-3468.14320