Microheterogeneity in Glycosylphosphatidylinositol Anchor Structures of Bovine Liver 5'-Nucleotidase

Taguchi, Ryo; Hamakawa, Noriaki; Harada-Nishida, Miwa; Fukui, Takafumi; Nojima, Kazutetsu; Ikezawa, Hiroh

doi:10.1021/bi00170a021

Cited by 43 publications

(28 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In support of this notion, a fourth mannose is present on 7 of 10 characterized mammalian protein-bound GPIs (6, 7, 26 -31, 41, 42). Six of the 7 Man 4 -GPIs were isolated from proteins purified directly from primary sources like homogenized organ tissue (6,26,28,29,31) or urine (27). Only 1 was from a protein purified from a cultured mouse cell line (30).…”

Section: Discussionmentioning

confidence: 99%

Human Smp3p Adds a Fourth Mannose to Yeast and Human Glycosylphosphatidylinositol Precursors in Vivo

Taron

Colussi

Wiedman³

et al. 2004

Journal of Biological Chemistry

View full text Add to dashboard Cite

Yeast and human glycosylphosphatidylinositol (GPI) precursors differ in the extent to which a fourth mannose is present as a side branch of the third core mannose. A fourth mannose addition to GPIs has scarcely been detected in studies of mammalian GPI synthesis but is an essential step in the Saccharomyces cerevisiae pathway. We report that human SMP3 encodes a functional homolog of the yeast Smp3 GPI fourth mannosyltransferase. Expression of hSMP3 in yeast complements growth and biochemical defects of smp3 mutants and permits in vivo mannosylation of trimannosyl (Man 3 )-GPIs. Immunolocalization shows that hSmp3p resides in the endoplasmic reticulum in human cells. Northern analysis of mRNA from human tissues and cell lines indicates that hSMP3 is expressed in most tissues, with the highest levels in brain and colon, but its mRNA is nearly absent from cultured human cell lines. Correspondingly, increasing expression of hSMP3 in cultured HeLa cells causes abundant formation of three putative tetramannosyl (Man 4 )-GPIs. Our data indicate that hSmp3p functions as a mannosyltransferase that adds a fourth mannose to certain Man 3 -GPIs during biosynthesis of the human GPI precursor, and suggest it may do so in a tissue-specific manner.Glycosylphosphatidylinositols (GPIs) 1 are essential glycolipids synthesized by all eukaryotes. Many GPIs become covalently attached to the carboxyl termini of various secretory proteins and serve to anchor them to the exterior face of the plasma membrane (1, 2). Others remain protein-free and are distributed in the membranes of major cellular organelles and the plasma membrane (3, 4). GPIs are synthesized in the endoplasmic reticulum (ER) by stepwise addition of components to phosphatidylinositol. The end product of GPI synthesis is a "complete precursor" (5) that is substrate for the GPI transamidase complex that attaches it to proteins. Many of the steps and enzymes of GPI precursor assembly are conserved between humans and Saccharomyces cerevisiae and produce precursors with a common core structure of EthN-PO 4 -6Man␣1,2Man␣1,6Man␣1,4GlcN␣1,6Ins-PO 4 -lipid. In both pathways, the glycan portion of the GPI may be modified further with side branching ethanolamine phosphate (EthN-P) moieties on the first and second mannoses (6 -19).A notable difference in GPI structure between yeast and mammals is the extent to which a fourth mannose (Man-4) is present as a ␣1,2-linked side branch of the third mannose (Man-3). In S. cerevisiae, late stage intermediates in GPI precursor synthesis (17, 19 -21), the presumed GPI transamidase substrates (5), and protein-bound GPIs (22) all contain four mannoses. Addition of Man-4 to trimannosyl-GPIs (Man 3 -GPIs) by the essential Smp3 mannosyltransferase is a mandatory step in yeast GPI precursor assembly which precedes the addition of the terminal EthN-P to Man-3 through which the GPI is ultimately attached to protein (23). Thus, it is probable that all yeast GPI transamidase substrates bear four mannoses. Conversely, studies of the synthesis of mammal...

show abstract

Section: Discussionmentioning

confidence: 99%

Human Smp3p Adds a Fourth Mannose to Yeast and Human Glycosylphosphatidylinositol Precursors in Vivo

Taron

Colussi

Wiedman³

et al. 2004

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…Deletion of the whole hydrophobic domain (17 amino acids) or of the entire cleaved-off domain (25 amino acids) resulted in secretion of the protein. The structures of the GPI anchors from bovine liver [257,258] and from bull seminal plasma [242] eN were characterized. They concurred with the glycan and lipid structures of mammalian GPI-anchored proteins [259].…”

Section: Glycosylationmentioning

confidence: 99%

Cellular function and molecular structure of ecto-nucleotidases

Zimmermann

Zebisch

Sträter

2012

Purinergic Signalling

878

922

View full text Add to dashboard Cite

Ecto-nucleotidases play a pivotal role in purinergic signal transmission. They hydrolyze extracellular nucleotides and thus can control their availability at purinergic P2 receptors. They generate extracellular nucleosides for cellular reuptake and salvage via nucleoside transporters of the plasma membrane. The extracellular adenosine formed acts as an agonist of purinergic P1 receptors. They also can produce and hydrolyze extracellular inorganic pyrophosphate that is of major relevance in the control of bone mineralization. This review discusses and compares four major groups of ectonucleotidases: the ecto-nucleoside triphosphate diphosphohydrolases, ecto-5′-nucleotidase, ecto-nucleotide pyrophosphatase/phosphodiesterases, and alkaline phosphatases. Only recently and based on crystal structures, detailed information regarding the spatial structures and catalytic mechanisms has become available for members of these four ecto-nucleotidase families. This permits detailed predictions of their catalytic mechanisms and a comparison between the individual enzyme groups. The review focuses on the principal biochemical, cell biological, catalytic, and structural properties of the enzymes and provides brief reference to tissue distribution, and physiological and pathophysiological functions.

show abstract

“…3. 30) On the one hand, Fig. 2 also shows that the moiety of inositol phospholipid must function as a hydrophobic anchor for each protein to attach to the membrane.…”

Section: Structures Of Gpi-anchors and Their Micro-heterogeneitymentioning

confidence: 99%