title: Epithelial membrane proteins induce membrane blebbing and interact with the P2X7 receptor C terminus.
abstract: The binding of extracellular ATP to the P2X(7) receptor opens an integral cation-permeable channel; it also leads to membrane blebbing and, in certain immune cells, interleukin-1beta secretion and eventual death. The latter three effects are unique to the P2X(7) receptor; also unique among P2X receptors is the long intracellular C terminus of the protein. We have shown that the C-terminal domain of the P2X(7) receptor is responsible for the cell blebbing phenotype. A screen for proteins that associate with the C-terminal domain of the P2X(7) receptor and might mediate the blebbing phenotype, identified epithelial membrane protein 2 (EMP-2). The interaction between EMP-2 and P2X(7) was confirmed biochemically by co-immunoprecipitation, co-purification, and glutathione S-transferase pull-down assays, and this interaction was entirely dependent on the C-terminal domain of P2X(7). The P2X(7) receptor also interacted with the other members of the epithelial membrane protein family (EMP-1, EMP-3, and PMP-22). All four EMPs were found to be expressed in HEK-293 cells and in THP-1 monocytes, which express P2X(7) receptors. Interestingly, the constitutive overexpression of any of the EMPs in HEK-293 cells led to cell blebbing, annexin V binding, and cell death, by a caspase-dependent pathway. These findings suggest that the P2X(7) C-terminal domain associates with EMPs, and this interaction may mediate some aspects of the downstream signaling following P2X(7) receptor activation.
authors.affiliation: Institute of Molecular Physiology, University of Sheffield S10 2TN, United Kingdom. H.L.Wilson@sheffield.ac.uk
authors.forename: Heather L
authors.initials: HL
authors.lastname: Wilson
authors.forename: Stuart A
authors.initials: SA
authors.lastname: Wilson
authors.forename: Annmarie
authors.initials: A
authors.lastname: Surprenant
authors.forename: R Alan
authors.initials: RA
authors.lastname: North
mesh_terms: D000595:Amino Acid Sequence; D017209:Apoptosis; D002460:Cell Line; D002462:Cell Membrane / Q000502:physiology*; D006801:Humans; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D009185:Myelin Proteins / Q000502:physiology; D011233:Precipitin Tests; D018048:Receptors, Purinergic P2 / Q000737:chemistry* / Q000378:metabolism; D058486:Receptors, Purinergic P2X7
chemical_list: C486403:EMP2 protein, human; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D009185:Myelin Proteins; C546468:P2RX7 protein, human; C546469:P2rx7 protein, mouse; C073687:PMP22 protein, human; C489545:Pmp22 protein, mouse; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7