title: Identification of proteins associating with glycosylphosphatidylinositol- anchored T-cadherin on the surface of vascular endothelial cells: role for Grp78/BiP in T-cadherin-dependent cell survival.
abstract: There is scant knowledge regarding how cell surface lipid-anchored T-cadherin (T-cad) transmits signals through the plasma membrane to its intracellular targets. This study aimed to identify membrane proteins colocalizing with atypical glycosylphosphatidylinositol (GPI)-anchored T-cad on the surface of endothelial cells and to evaluate their role as signaling adaptors for T-cad. Application of coimmunoprecipitation from endothelial cells expressing c-myc-tagged T-cad and high-performance liquid chromatography revealed putative association of T-cad with the following proteins: glucose-related protein GRP78, GABA-A receptor alpha1 subunit, integrin beta3, and two hypothetical proteins, LOC124245 and FLJ32070. Association of Grp78 and integrin beta3 with T-cad on the cell surface was confirmed by surface biotinylation and reciprocal immunoprecipitation and by confocal microscopy. Use of anti-Grp78 blocking antibodies, Grp78 small interfering RNA, and coexpression of constitutively active Akt demonstrated an essential role for surface Grp78 in T-cad-dependent survival signal transduction via Akt in endothelial cells. The findings herein are relevant in the context of both the identification of transmembrane signaling partners for GPI-anchored T-cad as well as the demonstration of a novel mechanism whereby Grp78 can influence endothelial cell survival as a cell surface signaling receptor rather than an intracellular chaperone.
authors.affiliation: Department of Research, Cardiovascular Laboratories, Basel University Hospital, Hebelstrasse 20, CH 4031 Basel, Switzerland. maria.filippova@unibas.ch
authors.forename: Maria
authors.initials: M
authors.lastname: Philippova
authors.forename: Danila
authors.initials: D
authors.lastname: Ivanov
authors.forename: Manjunath B
authors.initials: MB
authors.lastname: Joshi
authors.forename: Emmanouil
authors.initials: E
authors.lastname: Kyriakakis
authors.forename: Katharina
authors.initials: K
authors.lastname: Rupp
authors.forename: Taras
authors.initials: T
authors.lastname: Afonyushkin
authors.forename: Valery
authors.initials: V
authors.lastname: Bochkov
authors.forename: Paul
authors.initials: P
authors.lastname: Erne
authors.forename: Therese J
authors.initials: TJ
authors.lastname: Resink
mesh_terms: D019921:Biotinylation; D015820:Cadherins / Q000378:metabolism*; D002462:Cell Membrane; D002470:Cell Survival; D000091342:Endoplasmic Reticulum Chaperone BiP; D042783:Endothelial Cells / Q000166:cytology*; D017261:Glycosylphosphatidylinositols / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D039661:Integrin beta3 / Q000378:metabolism; D013058:Mass Spectrometry; D021962:Membrane Microdomains / Q000378:metabolism; D018613:Microscopy, Confocal; D008954:Models, Biological; D018832:Molecular Chaperones / Q000378:metabolism*; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D015820:Cadherins; D000091342:Endoplasmic Reticulum Chaperone BiP; D017261:Glycosylphosphatidylinositols; C099972:H-cadherin; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D039661:Integrin beta3; D018832:Molecular Chaperones; D016271:Proto-Oncogene Proteins c-myc