title: Obscurin and KCTD6 regulate cullin-dependent small ankyrin-1 (sAnk1.5) protein turnover.
abstract: Protein turnover through cullin-3 is tightly regulated by posttranslational modifications, the COP9 signalosome, and BTB/POZ-domain proteins that link cullin-3 to specific substrates for ubiquitylation. In this paper, we report how potassium channel tetramerization domain containing 6 (KCTD6) represents a novel substrate adaptor for cullin-3, effectively regulating protein levels of the muscle small ankyrin-1 isoform 5 (sAnk1.5). Binding of sAnk1.5 to KCTD6, and its subsequent turnover is regulated through posttranslational modification by nedd8, ubiquitin, and acetylation of C-terminal lysine residues. The presence of the sAnk1.5 binding partner obscurin, and mutation of lysine residues increased sAnk1.5 protein levels, as did knockdown of KCTD6 in cardiomyocytes. Obscurin knockout muscle displayed reduced sAnk1.5 levels and mislocalization of the sAnk1.5/KCTD6 complex. Scaffolding functions of obscurin may therefore prevent activation of the cullin-mediated protein degradation machinery and ubiquitylation of sAnk1.5 through sequestration of sAnk1.5/KCTD6 at the sarcomeric M-band, away from the Z-disk-associated cullin-3. The interaction of KCTD6 with ankyrin-1 may have implications beyond muscle for hereditary spherocytosis, as KCTD6 is also present in erythrocytes, and erythrocyte ankyrin isoforms contain its mapped minimal binding site.
authors.affiliation: School of Medicine, University of California, San Diego, La Jolla, CA 92093-0613, USA. slange@ucsd.edu
authors.forename: Stephan
authors.initials: S
authors.lastname: Lange
authors.forename: Sue
authors.initials: S
authors.lastname: Perera
authors.forename: Phildrich
authors.initials: P
authors.lastname: Teh
authors.forename: Ju
authors.initials: J
authors.lastname: Chen
mesh_terms: D000107:Acetylation; D048868:Adaptor Proteins, Signal Transducing / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D017487:Ankyrins / Q000378:metabolism*; D000075686:COP9 Signalosome Complex; D019556:COS Cells; D002522:Chlorocebus aethiops; D044842:Cullin Proteins / Q000378:metabolism*; D015870:Gene Expression; D018507:Gene Expression Regulation, Developmental; D055785:Gene Knockdown Techniques; D020662:Guanine Nucleotide Exchange Factors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D046912:Multiprotein Complexes / Q000378:metabolism; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000254:growth & development / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D000075687:NEDD8 Protein; D010447:Peptide Hydrolases / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D020033:Protein Isoforms / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D017346:Protein Serine-Threonine Kinases; D020836:Protein Structure, Quaternary; D034622:RNA Interference; D051381:Rats; D064067:Rho Guanine Nucleotide Exchange Factors; D020798:Two-Hybrid System Techniques; D054875:Ubiquitination; D014452:Ubiquitins / Q000378:metabolism
chemical_list: C110202:ANK1 protein, human; D048868:Adaptor Proteins, Signal Transducing; D017487:Ankyrins; C503645:CUL3 protein, human; D044842:Cullin Proteins; D020662:Guanine Nucleotide Exchange Factors; C559190:KCTD6 proetin, human; D046912:Multiprotein Complexes; D009124:Muscle Proteins; D000075687:NEDD8 Protein; C082860:NEDD8 protein, human; D020033:Protein Isoforms; D064067:Rho Guanine Nucleotide Exchange Factors; D014452:Ubiquitins; C578224:OBSCN protein, human; D017346:Protein Serine-Threonine Kinases; D010447:Peptide Hydrolases; D000075686:COP9 Signalosome Complex