title: Proteasomal degradation of Nck1 but not Nck2 regulates RhoA activation and actin dynamics.
abstract: The ubiquitously expressed adapter proteins Nck1/2 interact with a multitude of effector molecules to regulate diverse cellular functions including cytoskeletal dynamics. Here we show that Nck1, but not Nck2, is a substrate of c-Cbl-mediated ubiquitination. We uncover lysine 178 in Nck1 as the evolutionarily conserved ubiquitin acceptor site. We previously reported that synaptopodin, a proline-rich actin-binding protein, induces stress fibres by blocking the Smurf1-mediated ubiquitination of RhoA. We now find that synaptopodin competes with c-Cbl for binding to Nck1, which prevents the ubiquitination of Nck1 by c-Cbl. Gene silencing of c-Cbl restores Nck1 protein abundance and stress fibres in synaptopodin knockdown cells. Similarly, expression of c-Cbl-resistant Nck1(K178R) or Nck2 containing the SH3 domain 2 of Nck1 restores stress fibres in synaptopodin-depleted podocytes through activation of RhoA signalling. These findings reveal proteasomal regulation as a key factor in the distinct and non-redundant effects of Nck on RhoA-mediated actin dynamics.
authors.affiliation: 1] Department of Medicine, Harvard Medical School, Massachusetts General Hospital, Boston, Massachusetts 02129, USA [2].
authors.forename: Lisa
authors.initials: L
authors.lastname: Buvall
authors.forename: Priyanka
authors.initials: P
authors.lastname: Rashmi
authors.forename: Esther
authors.initials: E
authors.lastname: Lopez-Rivera
authors.forename: Svetlana
authors.initials: S
authors.lastname: Andreeva
authors.forename: Astrid
authors.initials: A
authors.lastname: Weins
authors.forename: Hanna
authors.initials: H
authors.lastname: Wallentin
authors.forename: Anna
authors.initials: A
authors.lastname: Greka
authors.forename: Peter
authors.initials: P
authors.lastname: Mundel
mesh_terms: D000199:Actins / Q000378:metabolism*; D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000378:metabolism*; D003599:Cytoskeleton / Q000235:genetics / Q000378:metabolism; D004789:Enzyme Activation; D057809:HEK293 Cells; D006801:Humans; D015513:Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011485:Protein Binding; D059748:Proteolysis; D050721:Proto-Oncogene Proteins c-cbl / Q000235:genetics / Q000378:metabolism; D054875:Ubiquitination; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D000199:Actins; D048868:Adaptor Proteins, Signal Transducing; C485544:NCK2 protein, human; C078332:Nck protein; D015513:Oncogene Proteins; D050721:Proto-Oncogene Proteins c-cbl; D046988:Proteasome Endopeptidase Complex; D020742:rhoA GTP-Binding Protein; C067419:CBL protein, human