The affected gene underlying the class K glycosylphosphatidylinositol (GPI) surface protein defect codes for the GPI transamidase

Ji, Yu; Nagarajan, Shanmugam; Knez, J J; Udenfriend, Sidney; Chen, R; Medof, M. Edward

doi:10.1073/pnas.94.23.12580

Cited by 75 publications

(77 citation statements)

References 25 publications

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“…Sequence comparisons suggest that the L. mexicana GPI8 protein is smaller than the S. cerevisiae and human homologues (38 vs. 46 kDa) and that it lacks the C-terminal hydrophobic domain that is thought to be involved in anchoring these other GPI8 proteins to the lumenal leaflet of the ER (Benghezal et al, 1996;Yu et al, 1997). Attachment of L. mexicana GPI8 to the ER membrane, where the protein will be able to interact with the preformed GPI anchor, may thus require one or more other integral membrane proteins.…”

Section: Discussionmentioning

confidence: 99%

“…Homologues of both of these proteins have now been identified in humans (Yu et al, 1997;Hiroi et al, 1998). It is believed that Gpi8p is the catalytic subunit (Yu et al, 1997). This protein shares significant homology with a family of previously characterized cysteine proteinases, the asparaginyl endopeptidases known as legumains (Benghezal et al, 1996), which were originally identified in the seeds of leguminous plants (Ishii, 1994).…”

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confidence: 92%

“…Yeast mutants defective in the functioning of these individual proteins accumulate preassembled GPI anchors and have no GPI-anchored proteins. Homologues of both of these proteins have now been identified in humans (Yu et al, 1997;Hiroi et al, 1998). It is believed that Gpi8p is the catalytic subunit (Yu et al, 1997).…”

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confidence: 99%

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Leishmania mexicanaMutants Lacking Glycosylphosphatidylinositol (GPI):Protein Transamidase Provide Insights into the Biosynthesis and Functions of GPI-anchored Proteins

Hilley

Zawadzki

McConville

et al. 2000

MBoC

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The major surface proteins of the parasitic protozoon Leishmania mexicana are anchored to the plasma membrane by glycosylphosphatidylinositol (GPI) anchors. We have cloned the L. mexicana GPI8 gene that encodes the catalytic component of the GPI:protein transamidase complex that adds GPI anchors to nascent cell surface proteins in the endoplasmic reticulum. Mutants lacking GPI8 (⌬GPI8) do not express detectable levels of GPI-anchored proteins and accumulate two putative protein-anchor precursors. However, the synthesis and cellular levels of other nonprotein-linked GPIs, including lipophosphoglycan and a major class of free GPIs, are not affected in the ⌬GPI8 mutant. Significantly, the ⌬GPI8 mutant displays normal growth in liquid culture, is capable of differentiating into replicating amastigotes within macrophages in vitro, and is infective to mice. These data suggest that GPI-anchored surface proteins are not essential to L. mexicana for its entry into and survival within mammalian host cells in vitro or in vivo and provide further support for the notion that free GPIs are essential for parasite growth. INTRODUCTIONLeishmania are protozoan parasites that cause a spectrum of diseases in humans. These parasites alternate between a flagellated promastigote stage that proliferates within the midgut of the sandfly vector and a nonmotile amastigote stage that invades mammalian macrophages, where they occupy the phagolysosome compartment. The cell surface of the promastigote stage is coated by a protective glycocalyx that comprises a number of glycosylphosphatidylinositol (GPI)-anchored glycoproteins, a complex GPI-anchored lipophosphoglycan (LPG), and a family of free GPIs (termed glycoinositolphospholipids [GIPLs]) Beverley and Turco, 1998; Figure 1). Components in this glycoclayx are thought to be essential for parasite survival and infectivity in the diverse host Beverley and Turco, 1998). The GPIanchored glycoproteins include an abundant metalloproteinase, termed gp63 or leishmanolysin, and the promastigote surface antigen (PSA2)/gp46 family of glycoproteins Murray et al., 1989;Frommel et al., 1990;Lohman et al., 1990). Gp63 has been shown to be proteolytically active against a wide variety of different peptide substrates and has been reported to act as a ligand for macrophage receptors, either directly or after opsonization with complement, to protect the parasites from complementmediated lysis and also to contribute to the pathology of lesion development (see Alexander and Russell, 1992;Joshi et al., 1998). However, the fact that these proteins are encoded by multicopy polymorphic genes (Button et al., 1989;Lohman et al., 1990;Symons et al., 1994) has hindered elucidation of their function by genetic analysis (Joshi et al., 1998). Moreover, surface expression of gp63 and PSA2 is dramatically down-regulated in the amastigote stage of some Leishmania species and variable within particular parasite populations of others (Bahr et al., 1993;Handman et al., 1995) such that the precise function of these parasite pro...

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Section: Discussionmentioning

confidence: 99%

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confidence: 92%

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Leishmania mexicanaMutants Lacking Glycosylphosphatidylinositol (GPI):Protein Transamidase Provide Insights into the Biosynthesis and Functions of GPI-anchored Proteins

Hilley

Zawadzki

McConville

et al. 2000

MBoC

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“…GPI8 (PIGK) is presumed to be the catalytic center of the enzyme. 12 To date, the expression pattern of the subunits of the GPIT complex remains unknown in most human cancers. In the present study, we aimed to evaluate the expression pattern of the GPIT subunits at both mRNA and protein levels and their functional contribution in a number of different human cancers.…”

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confidence: 99%

Profiling the expression pattern of GPI transamidase complex subunits in human cancer

et al. 2008

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The glycosylphosphatidylinositol transamidase complex (GPIT) consists of five subunits: PIG-U, PIG-T, GPAA1, PIG-S and GPI8, and is important in attaching GPI anchors to target proteins. On the basis of our previous reports incriminating PIG-U as an oncogene in bladder cancer and PIG-T and GPAA1 as oncogenes in breast cancer, we evaluated the expression pattern of the GPIT subunits in 19 different human cancers at both mRNA and protein levels. In general, our results demonstrate a more frequent expression of GPIT subunits in cancers than in normal. Among the 19 anatomic sites compared; breast, ovary and uterus showed consistent evidence of overexpression of specific GPIT subunits. There was also overexpression of PIG-U and GPI8 in lymphoma. In addition, non-small cell lung carcinoma showed significant overexpression of the GPIT subunits as compared to small cell lung carcinoma and normal lung tissue. Also, deregulation of specific GPIT subunits was seen in various other cancers. Forced overexpression of two GPIT subunits; PIG-S and GPI8 alone or in combination induced increased proliferation and invasion of breast cancer cells. Collectively, our study defines a trend involving the deregulated expression and the functional contribution of the GPIT subunits in various cancers with potential implications in diagnosis, prognosis and therapeutic intervention.

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“…PIG-S and Gpi17p, and PIG-T and Gpi16p are orthologous to each other, respectively (Fraering et al, 2001;Ohishi et al, 2001). All the proteins are essential for GPI transamidase as shown by their mutant cells (Yu et al, 1997;Ohishi et al, 2000Ohishi et al, , 2001. GPI8/Gpi8p are most likely catalytic subunits because they have homology to the cysteine proteases of the C13 family (Benghezal et al, 1996;Meyer et al, 2000;Ohishi et al, 2000) and GPI8 associates with substrate proteins (Spurway et al, 2001;Vidugiriene et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

Human PIG-U and Yeast Cdc91p Are the Fifth Subunit of GPI Transamidase That Attaches GPI-Anchors to Proteins

Hong

Ohishi

Kang

et al. 2003

MBoC

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Many eukaryotic proteins are anchored to the cell surface via glycosylphosphatidylinositol (GPI), which is posttranslationally attached to the carboxyl-terminus by GPI transamidase. The mammalian GPI transamidase is a complex of at least four subunits, GPI8, GAA1, PIG-S, and PIG-T. Here, we report Chinese hamster ovary cells representing a new complementation group of GPI-anchored protein-deficient mutants, class U. The class U cells accumulated mature and immature GPI and did not have in vitro GPI transamidase activity. We cloned the gene responsible, termed PIG-U, that encoded a 435-amino-acid hydrophobic protein. The GPI transamidase complex affinity-purified from cells expressing epitope-tagged-GPI8 contained PIG-U and four other known components. Cells lacking PIG-U formed complexes of the four other components normally but had no ability to cleave the GPI attachment signal peptide. Saccharomyces cerevisiae Cdc91p, with 28% amino acid identity to PIG-U, partially restored GPI-anchored proteins on the surface of class U cells. PIG-U and Cdc91p have a functionally important short region with similarity to a region conserved in long-chain fatty acid elongases. Taken together, PIG-U and the yeast orthologue Cdc91p are the fifth component of GPI transamidase that may be involved in the recognition of either the GPI attachment signal or the lipid portion of GPI

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The affected gene underlying the class K glycosylphosphatidylinositol (GPI) surface protein defect codes for the GPI transamidase

Cited by 75 publications

References 25 publications

Leishmania mexicanaMutants Lacking Glycosylphosphatidylinositol (GPI):Protein Transamidase Provide Insights into the Biosynthesis and Functions of GPI-anchored Proteins

Leishmania mexicanaMutants Lacking Glycosylphosphatidylinositol (GPI):Protein Transamidase Provide Insights into the Biosynthesis and Functions of GPI-anchored Proteins

Profiling the expression pattern of GPI transamidase complex subunits in human cancer

Human PIG-U and Yeast Cdc91p Are the Fifth Subunit of GPI Transamidase That Attaches GPI-Anchors to Proteins

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