May play an important role in the regulation of lymphoma cell growth. Interacts with a 16-kDa Leu-13 protein to form a complex possibly involved in signal transduction. May act as the viral receptor for HCV.
Interacting selectively and non-covalently with any protein or protein complex (a complex of two or more proteins that may include other nonprotein molecules).
Evidence
1:
Inferred from Physical InteractionUniProtKB
A murine mAb, 5A6 (IgG1), has been isolated by immunization with a human B lymphoma cell line and screening for growth inhibition. The antibody immunoprecipitated a single chain protein of 26 kDa from cell lysates made with Triton X-100 but additional proteins were precipitated when cell lysates were made with the milder detergent CHAPS (3-[3-cholamidopropyl)dimethylammonio)-1-propane sulfate). We have identified one of these coprecipitated molecules as the 16-kDa Leu-13 Ag. 5A6 and anti-Leu-13 showed similar, although not identical, reactivity, growth inhibition and temperature-dependent aggregation effects among hematolymphoid cell lines. The aggregation induced by 5A6 and anti-Leu-13 was not dependent on LFA-1 (lymphocyte function-associated Ag-1). The cell-surface expression of both TAPA-1 (target of an antiproliferative antibody-1) and Leu-13 could be down-modulated by binding to their respective antibodies and they could be reciprocally comodulated. These results suggest that TAPA-1 and Leu-13 form a complex on the cell surface and play a role in growth control through a common pathway.
Evidence
2:
Inferred from Physical InteractionUniProtKB
A novel Ig superfamily protein, EWI-2, was co-purified with tetraspanin protein CD81 under relatively stringent Brij 96 detergent conditions and identified by mass spectrometric protein sequencing. EWI-2 associated specifically with CD9 and CD81 but not with other tetraspanins or with integrins. Immunodepletion experiments indicated that EWI-2-CD9/CD81 interactions are highly stoichiometric, with approximately 70% of CD9 and CD81 associated with EWI-2 in an embryonic kidney cell line. The EWI-2 molecule was covalently cross-linked (in separate complexes) to both CD81 and CD9, suggesting that association is direct. EWI-2 is part of a novel Ig subfamily that includes EWI-F (F2alpha receptor regulatory protein (FPRP), CD9P-1), EWI-3 (IgSF3), and EWI-101 (CD101). All four members of this Ig subfamily contain a Glu-Trp-Ile (EWI) motif not seen in other Ig proteins. As shown previously, the EWI-F molecule likewise forms highly proximal, specific, and stoichiometric complexes with CD9 and CD81. Human and murine EWI-2 protein sequences are 91% identical, and transcripts in the two species are expressed in virtually every tissue tested. Thus, EWI-2 potentially contributes to a variety of CD9 and CD81 functions seen in different cell and tissue types.
Evidence
3:
Inferred from Physical InteractionUniProtKB
Formation of the immunological synapse between an antigen-presenting cell (APC) and a T cell leads to signal generation in both cells involved. In T cells, the lipid raft-associated transmembrane adaptor protein LAT plays a central role. Its phosphorylation is a crucial step in signal propagation, including the calcium response and mitogen-activated protein kinase activation, and largely depends on its association with the SLP76 adaptor protein. Here we report the discovery of a new palmitoylated transmembrane adaptor protein, termed SCIMP. SCIMP is expressed in B cells and other professional APCs and is localized in the immunological synapse due to its association with tetraspanin-enriched microdomains. In B cells, it is constitutively associated with Lyn kinase and becomes tyrosine phosphorylated after major histocompatibility complex type II (MHC-II) stimulation. When phosphorylated, SCIMP binds to the SLP65 adaptor protein and also to the inhibitory kinase Csk. While the association with SLP65 initiates the downstream signaling cascades, Csk binding functions as a negative regulatory loop. The results suggest that SCIMP is involved in signal transduction after MHC-II stimulation and therefore serves as a regulator of antigen presentation and other APC functions.
Evidence
4:
Inferred from Physical InteractionUniProtKB
Tetraspanins is a large family of membrane proteins that are implicated in cell proliferation, differentiation and tumor invasion. Specifically, the tetraspanin CD81 has been involved in cell proliferation but the mechanism is unknown. Here, we show that CD81 clustering stimulates ERK/MAPKinase activity and tyrosine phosphorylation of the adapter protein Shc in Huh7 cancer cells. In addition, overexpression of CD81 in HepG2 cells, NIH3T3 cells, and murine fibroblasts GD25 lacking the beta1 family of integrins induces cell proliferation and ERK/MAPKinase activation. Linked with this event, we observed an increase in CD81-associated type II phosphatidylinositol 4-kinase activity. A mutant in the PTB domain of Shc failed to interact with phosphoinositides and localize to the plasma membrane thus blocking CD81-induced ERK/MAPKinase activation. Therefore, we conclude that CD81 stimulates synthesis of phosphoinositides with the recruitment of Shc to the plasma membrane via PTB domain, and this sequence of events induces activation of ERK/MAPKinase. These findings define a novel mechanism of ERK/MAPKinase activation and tumor cell proliferation.
Tetraspanins is a large family of membrane proteins that are implicated in cell proliferation, differentiation and tumor invasion. Specifically, the tetraspanin CD81 has been involved in cell proliferation but the mechanism is unknown. Here, we show that CD81 clustering stimulates ERK/MAPKinase activity and tyrosine phosphorylation of the adapter protein Shc in Huh7 cancer cells. In addition, overexpression of CD81 in HepG2 cells, NIH3T3 cells, and murine fibroblasts GD25 lacking the beta1 family of integrins induces cell proliferation and ERK/MAPKinase activation. Linked with this event, we observed an increase in CD81-associated type II phosphatidylinositol 4-kinase activity. A mutant in the PTB domain of Shc failed to interact with phosphoinositides and localize to the plasma membrane thus blocking CD81-induced ERK/MAPKinase activation. Therefore, we conclude that CD81 stimulates synthesis of phosphoinositides with the recruitment of Shc to the plasma membrane via PTB domain, and this sequence of events induces activation of ERK/MAPKinase. These findings define a novel mechanism of ERK/MAPKinase activation and tumor cell proliferation.
A murine monoclonal antibody was identified by its ability to induce a reversible antiproliferative effect on a human lymphoma cell line. Immunoprecipitation studies revealed that the antibody reacted with a 26-kilodalton cell surface protein (TAPA-1). A diverse group of human cell lines, including hematolymphoid, neuroectodermal, and mesenchymal cells, expressed the TAPA-1 protein. Many of the lymphoid cell lines, in particular those derived from large cell lymphomas, were susceptible to the antiproliferative effects of the antibody. TAPA-1 may therefore play an important role in the regulation of lymphoma cell growth. A cDNA clone coding for TAPA-1 was isolated by using the monoclonal antibody to screen an expression library in COS cells. Analysis of the deduced amino acid sequence indicated that the protein is highly hydrophobic and that it contains four putative transmembrane domains and a potential N-myristoylation site. TAPA-1 showed strong homology with the CD37 leukocyte antigen and with the ME491 melanoma-associated antigen, both of which have been implicated in the regulation of cell growth.
The chemical reactions and pathways resulting in the formation of phosphatidylinositol, any glycophospholipid in which the sn-glycerol 3-phosphate residue is esterified to the 1-hydroxyl group of 1D-myo-inositol.
Tetraspanins is a large family of membrane proteins that are implicated in cell proliferation, differentiation and tumor invasion. Specifically, the tetraspanin CD81 has been involved in cell proliferation but the mechanism is unknown. Here, we show that CD81 clustering stimulates ERK/MAPKinase activity and tyrosine phosphorylation of the adapter protein Shc in Huh7 cancer cells. In addition, overexpression of CD81 in HepG2 cells, NIH3T3 cells, and murine fibroblasts GD25 lacking the beta1 family of integrins induces cell proliferation and ERK/MAPKinase activation. Linked with this event, we observed an increase in CD81-associated type II phosphatidylinositol 4-kinase activity. A mutant in the PTB domain of Shc failed to interact with phosphoinositides and localize to the plasma membrane thus blocking CD81-induced ERK/MAPKinase activation. Therefore, we conclude that CD81 stimulates synthesis of phosphoinositides with the recruitment of Shc to the plasma membrane via PTB domain, and this sequence of events induces activation of ERK/MAPKinase. These findings define a novel mechanism of ERK/MAPKinase activation and tumor cell proliferation.
The chemical reactions and pathways involving phosphatidylinositol, any glycophospholipid in which a sn-glycerol 3-phosphate residue is esterified to the 1-hydroxyl group of 1D-myo-inositol.
Tetraspanins is a large family of membrane proteins that are implicated in cell proliferation, differentiation and tumor invasion. Specifically, the tetraspanin CD81 has been involved in cell proliferation but the mechanism is unknown. Here, we show that CD81 clustering stimulates ERK/MAPKinase activity and tyrosine phosphorylation of the adapter protein Shc in Huh7 cancer cells. In addition, overexpression of CD81 in HepG2 cells, NIH3T3 cells, and murine fibroblasts GD25 lacking the beta1 family of integrins induces cell proliferation and ERK/MAPKinase activation. Linked with this event, we observed an increase in CD81-associated type II phosphatidylinositol 4-kinase activity. A mutant in the PTB domain of Shc failed to interact with phosphoinositides and localize to the plasma membrane thus blocking CD81-induced ERK/MAPKinase activation. Therefore, we conclude that CD81 stimulates synthesis of phosphoinositides with the recruitment of Shc to the plasma membrane via PTB domain, and this sequence of events induces activation of ERK/MAPKinase. These findings define a novel mechanism of ERK/MAPKinase activation and tumor cell proliferation.
Tetraspanins is a large family of membrane proteins that are implicated in cell proliferation, differentiation and tumor invasion. Specifically, the tetraspanin CD81 has been involved in cell proliferation but the mechanism is unknown. Here, we show that CD81 clustering stimulates ERK/MAPKinase activity and tyrosine phosphorylation of the adapter protein Shc in Huh7 cancer cells. In addition, overexpression of CD81 in HepG2 cells, NIH3T3 cells, and murine fibroblasts GD25 lacking the beta1 family of integrins induces cell proliferation and ERK/MAPKinase activation. Linked with this event, we observed an increase in CD81-associated type II phosphatidylinositol 4-kinase activity. A mutant in the PTB domain of Shc failed to interact with phosphoinositides and localize to the plasma membrane thus blocking CD81-induced ERK/MAPKinase activation. Therefore, we conclude that CD81 stimulates synthesis of phosphoinositides with the recruitment of Shc to the plasma membrane via PTB domain, and this sequence of events induces activation of ERK/MAPKinase. These findings define a novel mechanism of ERK/MAPKinase activation and tumor cell proliferation.
Tetraspanins is a large family of membrane proteins that are implicated in cell proliferation, differentiation and tumor invasion. Specifically, the tetraspanin CD81 has been involved in cell proliferation but the mechanism is unknown. Here, we show that CD81 clustering stimulates ERK/MAPKinase activity and tyrosine phosphorylation of the adapter protein Shc in Huh7 cancer cells. In addition, overexpression of CD81 in HepG2 cells, NIH3T3 cells, and murine fibroblasts GD25 lacking the beta1 family of integrins induces cell proliferation and ERK/MAPKinase activation. Linked with this event, we observed an increase in CD81-associated type II phosphatidylinositol 4-kinase activity. A mutant in the PTB domain of Shc failed to interact with phosphoinositides and localize to the plasma membrane thus blocking CD81-induced ERK/MAPKinase activation. Therefore, we conclude that CD81 stimulates synthesis of phosphoinositides with the recruitment of Shc to the plasma membrane via PTB domain, and this sequence of events induces activation of ERK/MAPKinase. These findings define a novel mechanism of ERK/MAPKinase activation and tumor cell proliferation.
Tetraspanins is a large family of membrane proteins that are implicated in cell proliferation, differentiation and tumor invasion. Specifically, the tetraspanin CD81 has been involved in cell proliferation but the mechanism is unknown. Here, we show that CD81 clustering stimulates ERK/MAPKinase activity and tyrosine phosphorylation of the adapter protein Shc in Huh7 cancer cells. In addition, overexpression of CD81 in HepG2 cells, NIH3T3 cells, and murine fibroblasts GD25 lacking the beta1 family of integrins induces cell proliferation and ERK/MAPKinase activation. Linked with this event, we observed an increase in CD81-associated type II phosphatidylinositol 4-kinase activity. A mutant in the PTB domain of Shc failed to interact with phosphoinositides and localize to the plasma membrane thus blocking CD81-induced ERK/MAPKinase activation. Therefore, we conclude that CD81 stimulates synthesis of phosphoinositides with the recruitment of Shc to the plasma membrane via PTB domain, and this sequence of events induces activation of ERK/MAPKinase. These findings define a novel mechanism of ERK/MAPKinase activation and tumor cell proliferation.
Tetraspanins is a large family of membrane proteins that are implicated in cell proliferation, differentiation and tumor invasion. Specifically, the tetraspanin CD81 has been involved in cell proliferation but the mechanism is unknown. Here, we show that CD81 clustering stimulates ERK/MAPKinase activity and tyrosine phosphorylation of the adapter protein Shc in Huh7 cancer cells. In addition, overexpression of CD81 in HepG2 cells, NIH3T3 cells, and murine fibroblasts GD25 lacking the beta1 family of integrins induces cell proliferation and ERK/MAPKinase activation. Linked with this event, we observed an increase in CD81-associated type II phosphatidylinositol 4-kinase activity. A mutant in the PTB domain of Shc failed to interact with phosphoinositides and localize to the plasma membrane thus blocking CD81-induced ERK/MAPKinase activation. Therefore, we conclude that CD81 stimulates synthesis of phosphoinositides with the recruitment of Shc to the plasma membrane via PTB domain, and this sequence of events induces activation of ERK/MAPKinase. These findings define a novel mechanism of ERK/MAPKinase activation and tumor cell proliferation.
The process that occurs after viral attachment by which a virion, or viral nucleic acid, breaches the plasma membrane or cell envelope and enters the host cell. The process ends when the viral nucleic acid is released into the host cell cytoplasm.
Tetraspanins is a large family of membrane proteins that are implicated in cell proliferation, differentiation and tumor invasion. Specifically, the tetraspanin CD81 has been involved in cell proliferation but the mechanism is unknown. Here, we show that CD81 clustering stimulates ERK/MAPKinase activity and tyrosine phosphorylation of the adapter protein Shc in Huh7 cancer cells. In addition, overexpression of CD81 in HepG2 cells, NIH3T3 cells, and murine fibroblasts GD25 lacking the beta1 family of integrins induces cell proliferation and ERK/MAPKinase activation. Linked with this event, we observed an increase in CD81-associated type II phosphatidylinositol 4-kinase activity. A mutant in the PTB domain of Shc failed to interact with phosphoinositides and localize to the plasma membrane thus blocking CD81-induced ERK/MAPKinase activation. Therefore, we conclude that CD81 stimulates synthesis of phosphoinositides with the recruitment of Shc to the plasma membrane via PTB domain, and this sequence of events induces activation of ERK/MAPKinase. These findings define a novel mechanism of ERK/MAPKinase activation and tumor cell proliferation.
Tetraspanins is a large family of membrane proteins that are implicated in cell proliferation, differentiation and tumor invasion. Specifically, the tetraspanin CD81 has been involved in cell proliferation but the mechanism is unknown. Here, we show that CD81 clustering stimulates ERK/MAPKinase activity and tyrosine phosphorylation of the adapter protein Shc in Huh7 cancer cells. In addition, overexpression of CD81 in HepG2 cells, NIH3T3 cells, and murine fibroblasts GD25 lacking the beta1 family of integrins induces cell proliferation and ERK/MAPKinase activation. Linked with this event, we observed an increase in CD81-associated type II phosphatidylinositol 4-kinase activity. A mutant in the PTB domain of Shc failed to interact with phosphoinositides and localize to the plasma membrane thus blocking CD81-induced ERK/MAPKinase activation. Therefore, we conclude that CD81 stimulates synthesis of phosphoinositides with the recruitment of Shc to the plasma membrane via PTB domain, and this sequence of events induces activation of ERK/MAPKinase. These findings define a novel mechanism of ERK/MAPKinase activation and tumor cell proliferation.
Viral protein involved in a direct and specific interaction with a host macromolecule. Viruses interact with many cellular pathways to achieve their replication cycle. Entry into the host cell, transport to the viral replication sites or viral budding are all steps that require interaction between the host and the virus. Additionally, the evasion from the host immune response requires a lot of viral proteins to associate with and inhibit cellular proteins with antiviral functions.
A reference proteome is a set of protein sequences derived from a complete proteome which constitutes a defined standard for a particular user community. Reference proteomes are manually defined according to a number of criteria. They cover the proteomes of well- studied model organisms and other proteomes of interest for biomedical and biotechnological research. Reference proteomes have been selected to provide broad coverage of the tree of life, and constitute a representative cross-section of the taxonomic diversity to be found within UniProtKB.
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