Cullin 3 Recognition Is Not a Universal Property among KCTD Proteins

Abstract

Cullin 3 (Cul3) recognition by BTB domains is a key process in protein ubiquitination. Among Cul3 binders, a great attention is currently devoted to KCTD proteins, which are implicated in fundamental biological processes. On the basis of the high similarity of BTB domains of these proteins, it has been suggested that the ability to bind Cul3 could be a general property among all KCTDs. In order to gain new insights into KCTD functionality, we here evaluated and/or quantified the binding of Cul3 to the BTB of KCTD proteins, which are known to be involved either in cullin-independent (KCTD12 and KCTD15) or in cullin-mediated (KCTD6 and KCTD11) activities. Our data indicate that KCTD6BTB and KCTD11BTB bind Cul3 with high affinity forming stable complexes with 4:4 stoichiometries. Conversely, KCTD12BTB and KCTD15BTB do not interact with Cul3, despite the high level of sequence identity with the BTB domains of cullin binding KCTDs. Intriguingly, comparative sequence analyses indicate that the capability of KCTD proteins to recognize Cul3 has been lost more than once in distinct events along the evolution. Present findings also provide interesting clues on the structural determinants of Cul3-KCTD recognition. Indeed, the characterization of a chimeric variant of KCTD11 demonstrates that the swapping of α2β3 loop between KCTD11BTB and KCTD12BTB is sufficient to abolish the ability of KCTD11BTB to bind Cul3. Finally, present findings, along with previous literature data, provide a virtually complete coverage of Cul3 binding ability of the members of the entire KCTD family.

Cullin E3 Ligase Activity Is Required for Myoblast Differentiation

“…Thereby, our data add for the first time ZBTB38 to the short list of BTB-domain proteins that were recently shown to not bind to cullin-3 [59, 60]. …”

Genes regulated by potassium channel tetramerization domain containing 15 (Kctd15) in the developing neural crest

“…Kctd5, Kctd6 and Kctd11 bind Cullin 3 and act as adapters mediating the interactions of E3 ubiquitin ligases with their substrates (Balasco et al, 2014; Bayon et al, 2008; Canettieri et al, 2010; Chen et al, 2009; Correale et al, 2011). While other Kctd proteins also have been reported to bind Cullin 3, this has been contradicted in recent work (Smaldone et al, 2015). Kctd8, Kctd12 and Kctd16 associate with GABA receptors, modulating their activity (Rajalu et al, 2015); these genes also show striking left/right asymmetry in their expression in the brain (Gamse et al, 2005).…”

KCTD: A new gene family involved in neurodevelopmental and neuropsychiatric disorders

“…Then, rapid deactivation/desensitization of GIRK channels would subsequently occur when KCTD12 H1 sequesters Gβγ away from these channels . A role for KCTD12 in GABA B ‐Gβγ signaling to regulate potassium channel activity is not mutually exclusive with a role as a cullin‐3 adaptor (e.g., to degrade Gα), except that the α2β3 loop of KCTD12 is predicted to interfere with cullin‐3 interactions . Therefore, any congruency between the cullin‐binding KCTDs and GTPase signaling KCTDs is currently unresolved but may represent independent functions of the same or different KCTD family proteins.…”

“…This proposed adaptor function for KCTD proteins could potentially underlie the diverse biological processes reported for KCTD proteins, including DNA replication (KCTD10 and TNFAIP1), transcription inhibition (KCTD1 and KCTD15), regulation of Rho GTPases in brain development (KCTD13), suppression of hedgehog signaling (KCTD11), autophagy induction and amino acid signaling to mTORC1 (KCTD11), and more (Table ). However, other KCTDs appear to lack the ability to bind cullin‐3, implying distinct biochemical mechanisms . For example, several KCTD family proteins (e.g., KCTD12 and KCTD13) may alter neuronal activity and other signaling pathways by regulating diverse types of GTPases .…”