title: ErbB-4 and TNF-alpha converting enzyme localization to membrane microdomains.
abstract: Sequential proteolytic processing of ErbB-4 occurs in response to ligand addition. Here, we assess the localization of cleavable and non-cleavable ErbB-4 isoforms to membrane microdomains using three methodologies: (1) Triton X-100-insolubility, (2) Brij98-insolubility, and (3) detergent-free density gradient centrifugation. Whereas ErbB-4 translocated to a Triton X-100-insoluble fraction upon treatment of T47D cells with heregulin, it constitutively associated with a Brij98-insoluble fraction and a lipid raft fraction isolated using detergent-free methodology. Comparison of cleavable and non-cleavable isoforms of ErbB-4 revealed that both ErbB-4 isoforms are constitutively localized to either a Triton X-100-soluble or Brij98-insoluble fraction. In contrast, addition of heregulin resulted in translocation of the cleavable isoform to a detergent-free lipid raft. Tumor necrosis factor-alpha converting enzyme (TACE), the ectodomain secretase for ErbB-4, was present predominantly in its mature active form in most microdomains analyzed. These data suggest the assembly of ErbB-4 ectodomain cleavage apparatus in a membrane microdomain.
authors.affiliation: Vanderbilt University School of Medicine, Department of Biochemistry, Nashville, TN 37232-0146, USA.
authors.forename: Kristina W
authors.initials: KW
authors.lastname: Thiel
authors.forename: Graham
authors.initials: G
authors.lastname: Carpenter
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D066246:ErbB Receptors / Q000378:metabolism*; D021962:Membrane Microdomains / Q000378:metabolism*; D066247:Receptor, ErbB-4; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism*
chemical_list: D014409:Tumor Necrosis Factor-alpha; D066246:ErbB Receptors; D066247:Receptor, ErbB-4