KCTD5 Forms Hetero-Oligomeric Complexes with Various Members of the KCTD Protein Family.

Potassium Channel Tetramerization Domain 5 (KCTD5) regulates diverse aspects of physiology, ranging from neuronal signaling to colorectal cancer. A key feature of KCTD5 is its self-assembly into multi-subunit oligomers that seemingly enables participation in an array of protein-protein interactions. KCTD5 has recently been reported to form hetero-oligomeric complexes with two similar KCTDs (KCTD2 and KCTD17). However, it is not known if KCTD5 forms hetero-oligomeric complexes with the remaining KCTD protein family which contains over two dozen members. Here, we demonstrate that KCTD5 interacts with various KCTD proteins when assayed through co-immunoprecipitation in lysed cells. We reinforced this dataset by examining KCTD5 interactions in a live-cell bioluminescence resonance energy transfer (BRET)-based approach. Finally, we developed an IP-luminescence approach to map regions on KCTD5 required for interaction with a selection of KCTD that have established roles in neuronal signaling. We report that different regions on KCTD5 are responsible for uniquely contributing to interactions with other KCTD proteins. While our results help unravel additional interaction partners for KCTD5, they also reveal additional complexities in KCTDs' biology. Moreover, our findings also suggest that KCTD hetero-oligomeric interactions may occur throughout the KCTD family.

Multiple potassium channel tetramerization domain (KCTD) family members interact with Gßγ, with effects on cAMP signaling.

G protein-coupled receptors (GPCRs) initiate an array of intracellular signaling programs by activating heterotrimeric G proteins (Gα and Gßγ subunits). Therefore, G protein modifiers are well positioned to shape GPCR pharmacology. A few members of the potassium channel tetramerization domain (KCTD) protein family have been found to adjust G protein signaling through interaction with Gßγ. However, comprehensive details on the KCTD interaction with Gßγ remain unresolved. Here, we report that nearly all the 25 KCTD proteins interact with Gßγ. In this study, we screened Gßγ interaction capacity across the entire KCTD family using two parallel approaches. In a live cell bioluminescence resonance energy transfer-based assay, we find that roughly half of KCTD proteins interact with Gßγ in an agonist-induced fashion, whereas all KCTD proteins except two were found to interact through coimmunoprecipitation. We observed that the interaction was dependent on an amino acid hot spot in the C terminus of KCTD2, KCTD5, and KCTD17. While KCTD2 and KCTD5 require both the Bric-à-brac, Tramtrack, Broad complex domain and C-terminal regions for Gßγ interaction, we uncovered that the KCTD17 C terminus is sufficient for Gßγ interaction. Finally, we demonstrated the functional consequence of the KCTD-Gßγ interaction by examining sensitization of the adenylyl cyclase-cAMP pathway in live cells. We found that Gßγ-mediated sensitization of adenylyl cyclase 5 was blunted by KCTD. We conclude that the KCTD family broadly engages Gßγ to shape GPCR signal transmission.

Members of the KCTD family are major regulators of cAMP signaling.

Cyclic adenosine monophosphate (cAMP) is a pivotal second messenger with an essential role in neuronal function. cAMP synthesis by adenylyl cyclases (AC) is controlled by G protein-coupled receptor (GPCR) signaling systems. However, the network of molecular players involved in the process is incompletely defined. Here, we used CRISPR/Cas9-based screening to identify that members of the potassium channel tetradimerization domain (KCTD) family are major regulators of cAMP signaling. Focusing on striatal neurons, we show that the dominant isoform KCTD5 exerts its effects through an unusual mechanism that modulates the influx of Zn2+ via the Zip14 transporter to exert unique allosteric effects on AC. We further show that KCTD5 controls the amplitude and sensitivity of stimulatory GPCR inputs to cAMP production by Gßγ-mediated AC regulation. Finally, we report that KCTD5 haploinsufficiency in mice leads to motor deficits that can be reversed by chelating Zn2+ Together, our findings uncover KCTD proteins as major regulators of neuronal cAMP signaling via diverse mechanisms.