A glycophospholipid anchor is required for Qa-2-mediated T cell activation

Robinson, Peter; Millrain, M. M.; Antoniou, Jane; Simpson, Elizabeth; Mellor, Andrew L.

doi:10.1038/342085a0

Cited by 163 publications

(85 citation statements)

References 20 publications

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“…Adipocytes were isolated from epididymal fat pads of 140-to 160-g male Wistar rats under sterile conditions as described previously (Rodbell, 1964) with the following modifications: The fat tissue (0.5-1 g) was minced in 50-mL polyethylene vials containing 3 mL of KRH buffer (10 mM HEPES/KOH, pH 7.4, 125 mM NaCl, 5.5 mM KCl, 2 mM C a C h l . 5 mM MgS04,2.5 mM NaH2P04, 2.5% BSA, and 2 mM D-glucose) and incubated (10-20 min, 37 "C) with collagenase (0.1 mg/mL routinely, or as indicated in the figure legends) under gentle stirring with a Tefloncoated bar.…”

Section: Methodsmentioning

confidence: 99%

Membrane Association of Lipoprotein Lipase and a cAMP-Binding Ectoprotein in Rat Adipocytes

Müller

Wetekam²,

Jung³

et al. 1994

Biochemistry

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CAMP-binding ectoprotein (Gcel ) and lipoprotein lipase (LPL) are anchored to plasma membranes of rat adipocytes by glycosylphosphatidylinositol (GPI) moieties as demonstrated by cleavage by bacterial phosphatidylinositol-specific phospholipase C (PI-PLC), reactivity with anti-crossreacting determinant antibodies (anti-CRD), and metabolic labeling with radiolabeled palmitic acid and myoinositol. Quantitative release from the membrane of LPL and Gcel requires both lipolytic removal of their GPI anchors and the presence of either 2 M NaCl or 1 mM inositol 1,2-cyclic monophosphate or inositol 1 -monophosphate. PI-PLC-cleaved and released LPL or Gcel reassociates with isolated plasma membranes of rat adipocytes and, less efficiently, with membranes of 3T3 fibroblasts. The specificity of the reassociation is demonstrated (i) by its inhibition after pretreatment of the membranes with trypsin, (ii) by its competition with inositol 1,2-cyclic monophosphate and inositol 1-monophosphate in a concentration-dependent manner, and (iii) by the limited number of binding sites. Enzymic or chemical removal as well as masking with anti-CRD antibodies of the terminal inositol (cyclic) monophosphate moiety of hydrophilic Gcel and LPL significantly impairs the reassociation. These data suggest that in rat adipocytes GPI-proteins are not readily released from the cell surface upon lipolytic cleavage, but remain associated through a receptor which specifically recognizes the terminal inositol (cyclic) monophosphate epitope of the (G)PI-PLCcleaved GPI moiety. This interaction may have implications for the regulated membrane release of GPIproteins and for their possible internalization.GPI-proteins,' a subclass of ectoproteins in both lower and higher eucaryotes, are anchored to the outer leaflet of the plasma membrane by covalently attached GPI glycolipids which are characterized by a high degree of structural conservation from yeast to man. Their linear core structure is built from phosphatidylinositol bound via nonacetylated glucosamine to three mannose residues. The nonreducing end is linked to ethanolamine via a phosphodiester bridge. From this conserved core glycan various carbohydrate and/ or phosphoethanolamine residues may branch off [for a review see Ferguson and Williams (1988), Low (1989), and McConville and Ferguson (1993l. During the biosynthesis of GPI-proteins, the amino group of ethanolamine of the complete preformed GPI structure is coupled in a pseudo transpeptidation reaction to the carboxy terminus of the mature fully translated polypeptide chain, thereby replacing a transmembrane domain present in the protein precursor [for a review see Doering et al. (1990) and Thomas et al. (1990)l.Despite the lack of a cytoplasmic domain someGPI-proteins seem to have important roles in transmembrane signaling

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Section: Methodsmentioning

confidence: 99%

Membrane Association of Lipoprotein Lipase and a cAMP-Binding Ectoprotein in Rat Adipocytes

Müller

Wetekam²,

Jung³

et al. 1994

Biochemistry

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“…The pathways are not well understood, but the presence of a GPI anchor seems to be essential [137][138][139][140]. It is interesting that T cell activation by ligation of CD73 in mice requires the fyn tyrosine kinase [130], suggesting a possible signaling pathway.…”

Section: ј Nucleotidase In T Cell Activation: Role Of the Gpi Anchormentioning

confidence: 99%

Ecto-enzymes: physiology meets pathology

Goding

2000

Journal of Leukocyte Biology

101

111

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Ecto-enzymes are catalytic membrane proteins with their active sites outside the cell. They include cholinesterase, which inactivates acetylcholine, and angiotensin-converting enzyme, which converts angiotensin I to biologically active angiotensin II, and numerous other peptidases, transpeptidases, nucleotidases, phosphodiesterases, and phosphatases. Many CD antigens of leukocytes are ecto-enzymes; some CD antigens for which no function is currently known are probably ectoenzymes. Expression is highly regulated and correlated with differentiation and activation. Some are highly restricted in distribution; others are ubiquitous. Many are shared between leukocytes and non-hematogenous cells. Biological functions appear to depend on the type and location of the cell in which expression occurs, and include recycling of nutrients, local control of response to cytokines and hormones, bone formation, cell mobility, invasion, and metastasis. Many novel regulatory functions of ecto-enzymes remain to be discovered, and may reveal new mechanisms of local extracellular control of cellular function.

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“…1), one as part of the internal mannose-6-phosphate ethanolamine bridge; the other connects the glycan to the lipid moiety in intact GPI-linked molecules, or it is a part of an inositol-l,2 cyclic phosphate group in GPI-linked molecules that have been cleaved with PI-PLC. In view of the role of the MPR as a growth-regulatory molecule and the observation that under certain circumstances GPI-linked molecules may mediate cell signalling [21], we have pursued further our initial observation on the binding of the receptor to a GPI-linked molecule. In particular, our aim has been to determine which of these two phosphate groups (P1 or P2, in Fig.…”

Section: Introductionmentioning

confidence: 99%

The cation‐independent mannose‐6‐phosphate receptor binds to soluble GPI‐linked proteins via mannose‐6‐phosphate

Green¹,

Ferguson²,

Robinson³

et al. 1995

FEBS Letters

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The cation-independent mannose-6-phosphatelinsulinlike growth factor II receptor has been observed to bind to soluble forms of glycosyl-phosphatidylinositol-linked molecules, one of mammalian origin (rat Thy-1) and two of protozoan origins. Of the two phosphate groups found on the soluble forms of the protozoan glycosyl-phosphatidylinositol-linked molecules: (i) the internal mannose-6-phosphate diester (which forms a part of the ethanolamine bridge) and (ii) the inositol-l,2 cyclic phosphate group (which arises after cleavage of the membrane associated form with phosphatidylinositol-specific phospholipase C), only the former appears to be recognized by the mannose-6-phosphate/ insulin-like growth factor II receptor, as mild acid hydrolysis which destroys the latter has been observed not to affect the receptor binding site.

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A glycophospholipid anchor is required for Qa-2-mediated T cell activation

Cited by 163 publications

References 20 publications

Membrane Association of Lipoprotein Lipase and a cAMP-Binding Ectoprotein in Rat Adipocytes

Membrane Association of Lipoprotein Lipase and a cAMP-Binding Ectoprotein in Rat Adipocytes

Ecto-enzymes: physiology meets pathology

The cation‐independent mannose‐6‐phosphate receptor binds to soluble GPI‐linked proteins via mannose‐6‐phosphate

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