title: The E3 ubiquitin ligase WWP1 selectively targets HER4 and its proteolytically derived signaling isoforms for degradation.
abstract: In general, epidermal growth factor receptor family members stimulate cell proliferation. In contrast, at least one HER4 isoform, JM-a/Cyt1, inhibits cell growth after undergoing a two-step proteolytic cleavage that first produces a membrane-anchored 80-kDa fragment (m80(HER4)) and subsequently liberates a soluble 80-kDa fragment, s80(HER4). Here we report that s80(HER4) Cyt1 action increased the expression of WWP1 (for WW domain-containing protein 1), an E3 ubiquitin ligase, but not other members of the Nedd4 E3 ligase family. The HER4 Cyt1 isoform contains three proline-rich tyrosine (PY) WW binding motifs, while Cyt2 has only two. WWP1 binds to all three Cyt1 PY motifs; the interaction with PY2 found exclusively in Cyt1 was strongest. WWP1 ubiquitinated and caused the degradation of HER4 but not of EGFR, HER2, or HER3. The HER4-WWP1 interaction also accelerated WWP1 degradation. Membrane HER4 (full length and m80(HER4), the product of the first proteolytic cleavage) were the preferred targets of WWP1, correlating with the membrane localization of WWP1. Conversely s80(HER4), a poorer WWP1 substrate, was found in the cell nucleus, while WWP1 was not. Deletion of the C2 membrane association domain of WWP1 allowed more efficient s80(HER4) degradation, suggesting that WWP1 is normally part of a membrane complex that regulates HER4 membrane species levels, with a predilection for the growth-inhibitory Cyt1 isoform. Finally, WWP1 expression diminished HER4 biologic activity in MCF-7 cells. We previously showed that nuclear s80(HER4) is ubiquitinated and degraded by the anaphase-promoting complex, suggesting that HER4 ubiquitination within specific cellular compartments helps regulate the unique HER4 signaling capabilities.
authors.affiliation: UNC Lineberger Comprehensive Cancer Center, University of North Carolina Chapel Hill, Chapel Hill, North Carolina 27599, USA.
authors.forename: Shu-Mang
authors.initials: SM
authors.lastname: Feng
authors.forename: Rebecca S
authors.initials: RS
authors.lastname: Muraoka-Cook
authors.forename: Debra
authors.initials: D
authors.lastname: Hunter
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Sandahl
authors.forename: Laura S
authors.initials: LS
authors.lastname: Caskey
authors.forename: Keiji
authors.initials: K
authors.lastname: Miyazawa
authors.forename: Azeddine
authors.initials: A
authors.lastname: Atfi
authors.forename: H Shelton
authors.initials: HS
authors.lastname: Earp
mesh_terms: D000818:Animals; D019556:COS Cells; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000201:enzymology; D002522:Chlorocebus aethiops; D004795:Enzyme Stability; D066246:ErbB Receptors / Q000737:chemistry / Q000378:metabolism*; D005786:Gene Expression Regulation; D006801:Humans; D051379:Mice; D008970:Molecular Weight; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D011485:Protein Binding; D020033:Protein Isoforms / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D066247:Receptor, ErbB-4; D015398:Signal Transduction; D012995:Solubility; D013347:Subcellular Fractions / Q000201:enzymology; D013379:Substrate Specificity; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D020033:Protein Isoforms; D012333:RNA, Messenger; C471642:WWP1 protein, human; D044767:Ubiquitin-Protein Ligases; C587689:ERBB4 protein, human; D066246:ErbB Receptors; C587690:Erbb4 protein, mouse; D066247:Receptor, ErbB-4; D046988:Proteasome Endopeptidase Complex