Members of the KCTD family are major regulators of cAMP signaling

Structural studies of KCTD1 and its disease-causing mutant P20S provide insights into the protein function and misfunction

Members of the KCTD protein family play key roles in fundamental physio-pathological processes including cancer, neurodevelopmental/neuropsychiatric, and genetic diseases. Here, we report the crystal structure of the KCTD1 P20S mutant, which causes the scalp-ear-nipple syndrome, and molecular dynamics (MD) data on the wild-type protein. Surprisingly, the structure unravels that the N-terminal region, which precedes the BTB domain (preBTB) and bears the disease-associated mutation, adopts a folded polyproline II (PPII) state. The KCTD1 pentamer is characterized by an intricate architecture in which the different subunits mutually exchange domains to generate a closed domain swapping motif. Indeed, the BTB of each chain makes peculiar contacts with the preBTB and the C-terminal domain (CTD) of an adjacent chain. The BTB-preBTB interaction consists of a PPII-PPII recognition motif whereas the BTB-CTD contacts are mediated by an unusual (+/-) helix discontinuous association. The inspection of the protein structure, along with the data emerged from the MD simulations, provides an explanation of the pathogenicity of the P20S mutation and unravels the role of the BTB-preBTB interaction in the insurgence of the disease. Finally, the presence of potassium bound to the central cavity of the CTD pentameric assembly provides insights into the role of KCTD1 in metal homeostasis.

Emerging modes of regulation of neuromodulatory G protein-coupled receptors

In the nervous system, G protein-coupled receptors (GPCRs) control neuronal excitability, synaptic transmission, synaptic plasticity, and, ultimately, behavior through spatiotemporally precise initiation of a variety of signaling pathways. However, despite their critical importance, there is incomplete understanding of how these receptors are regulated to tune their signaling to specific neurophysiological contexts. A deeper mechanistic picture of neuromodulatory GPCR function is needed to fully decipher their biological roles and effectively harness them for the treatment of neurological and psychiatric disorders. In this review, we highlight recent progress in identifying novel modes of regulation of neuromodulatory GPCRs, including G protein- and receptor-targeting mechanisms, receptor-receptor crosstalk, and unique features that emerge in the context of chemical synapses. These emerging principles of neuromodulatory GPCR tuning raise critical questions to be tackled at the molecular, cellular, synaptic, and neural circuit levels in the future.

Smooth operator(s): dialing up and down neurotransmitter responses by G-protein regulators

G-protein-coupled receptors (GPCRs) are essential mediators of neuromodulation and prominent pharmacological targets. While activation of heterotrimeric G-proteins (Gαβɣ) by GPCRs is essential in this process, much less is known about the postreceptor mechanisms that influence G-protein activity. Neurons express G-protein regulators that shape the amplitude and kinetics of GPCR-mediated synaptic responses. Although many of these operate by directly altering how G-proteins handle guanine-nucleotides enzymatically, recent discoveries have revealed alternative mechanisms by which GPCR-stimulated G-protein responses are modulated at the synapse. In this review, we cover the molecular basis for, and consequences of, the action of two G-protein regulators that do not affect the enzymatic activity of G-proteins directly: Gα inhibitory interacting protein (GINIP), which binds active Gα subunits, and potassium channel tetramerization domain-containing 12 (KCTD12), which binds active Gβγ subunits.

KCTD proteins regulate morphine dependence via heterologous sensitization of adenylyl cyclase 1 in mice

Heterologous sensitization of adenylyl cyclase (AC) results in elevated cAMP signaling transduction that contributes to drug dependence. Inhibiting cullin3-RING ligases by blocking the neddylation of cullin3 abolishes heterologous sensitization, however, the modulating mechanism remains uncharted. Here, we report an essential role of the potassium channel tetramerization domain (KCTD) protein 2, 5, and 17, especially the dominant isoform KCTD5 in regulating heterologous sensitization of AC1 and morphine dependence via working with cullin3 and the cullin-associated and neddylation-dissociated 1 (CAND1) protein. In cellular models, we observed enhanced association of KCTD5 with Gβ and cullin3, along with elevated dissociation of Gβ from AC1 as well as of CAND1 from cullin3 in heterologous sensitization of AC1. Given binding of CAND1 inhibits the neddylation of cullin3, we further elucidated that the enhanced interaction of KCTD5 with both Gβ and cullin3 promoted the dissociation of CAND1 from cullin3, attenuated the inhibitory effect of CAND1 on cullin3 neddylation, ultimately resulted in heterologous sensitization of AC1. The paraventricular thalamic nucleus (PVT) plays an important role in mediating morphine dependence. Through pharmacological and biochemical approaches, we then demonstrated that KCTD5/cullin3 regulates morphine dependence via modulating heterologous sensitization of AC, likely AC1 in PVT in mice. In summary, the present study revealed the underlying mechanism of heterologous sensitization of AC1 mediated by cullin3 and discovered the role of KCTD proteins in regulating morphine dependence in mice.

Identifying pleiotropic genes via the composite test amidst the complexity of polygenic traits

Identifying the causal relationship between genotype and phenotype is essential to expanding our understanding of the gene regulatory network spanning the molecular level to perceptible traits. A pleiotropic gene can act as a central hub in the network, influencing multiple outcomes. Identifying such a gene involves testing under a composite null hypothesis where the gene is associated with, at most, one trait. Traditional methods such as meta-analyses of top-hit $P$-values and sequential testing of multiple traits have been proposed, but these methods fail to consider the background of genome-wide signals. Since Huang's composite test produces uniformly distributed $P$-values for genome-wide variants under the composite null, we propose a gene-level pleiotropy test that entails combining the aforementioned method with the aggregated Cauchy association test. A polygenic trait involves multiple genes with different functions to co-regulate mechanisms. We show that polygenicity should be considered when identifying pleiotropic genes; otherwise, the associations polygenic traits initiate will give rise to false positives. In this study, we constructed gene-trait functional modules using the results of the proposed pleiotropy tests. Our analysis suite was implemented as an R package PGCtest. We demonstrated the proposed method with an application study of the Taiwan Biobank database and identified functional modules comprising specific genes and their co-regulated traits.

KCTD Proteins Have Redundant Functions in Controlling Cellular Growth

We explored the functional redundancy of three structurally related KCTD (Potassium Channel Tetramerization Domain) proteins, KCTD2, KCTD5, and KCTD17, by progressively knocking them out in HEK 293 cells using CRISPR/Cas9 genome editing. After validating the knockout, we assessed the effects of progressive knockout on cell growth and gene expression. We noted that the progressive effects of knockout of KCTD isoforms on cell growth were most pervasive when all three isoforms were deleted, suggesting some functions were conserved between them. This was also reflected in progressive changes in gene expression. Our previous work indicated that Gβ1 was involved in the transcriptional control of gene expression, so we compared the gene expression patterns between GNB1 and KCTD KO. Knockout of GNB1 led to numerous changes in the expression levels of other G protein subunit genes, while knockout of KCTD isoforms had the opposite effect, presumably because of their role in regulating levels of Gβ1. Our work demonstrates a unique relationship between KCTD proteins and Gβ1 and a global role for this subfamily of KCTD proteins in maintaining the ability of cells to survive and proliferate.

Structure and dynamics of a pentameric KCTD5/CUL3/Gβγ E3 ubiquitin ligase complex

Heterotrimeric G proteins can be regulated by posttranslational modifications, including ubiquitylation. KCTD5, a pentameric substrate receptor protein consisting of an N-terminal BTB domain and a C-terminal domain, engages CUL3 to form the central scaffold of a cullin-RING E3 ligase complex (CRL3KCTD5) that ubiquitylates Gβγ and reduces Gβγ protein levels in cells. The cryo-EM structure of a 5:5:5 KCTD5/CUL3NTD/Gβ1γ2 assembly reveals a highly dynamic complex with rotations of over 60° between the KCTD5BTB/CUL3NTD and KCTD5CTD/Gβγ moieties of the structure. CRL3KCTD5 engages the E3 ligase ARIH1 to ubiquitylate Gβγ in an E3-E3 superassembly, and extension of the structure to include full-length CUL3 with RBX1 and an ARIH1~ubiquitin conjugate reveals that some conformational states position the ARIH1~ubiquitin thioester bond to within 10 Å of lysine-23 of Gβ and likely represent priming complexes. Most previously described CRL/substrate structures have consisted of monovalent complexes and have involved flexible peptide substrates. The structure of the KCTD5/CUL3NTD/Gβγ complex shows that the oligomerization of a substrate receptor can generate a polyvalent E3 ligase complex and that the internal dynamics of the substrate receptor can position a structured target for ubiquitylation in a CRL3 complex.

BTB domain mutations perturbing KCTD15 oligomerisation cause a distinctive frontonasal dysplasia syndrome

INTRODUCTION

KCTD15 encodes an oligomeric BTB domain protein reported to inhibit neural crest formation through repression of Wnt/beta-catenin signalling, as well as transactivation by TFAP2. Heterozygous missense variants in the closely related paralogue KCTD1 cause scalp-ear-nipple syndrome.

METHODS

Exome sequencing was performed on a two-generation family affected by a distinctive phenotype comprising a lipomatous frontonasal malformation, anosmia, cutis aplasia of the scalp and/or sparse hair, and congenital heart disease. Identification of a de novo missense substitution within KCTD15 led to targeted sequencing of DNA from a similarly affected sporadic patient, revealing a different missense mutation. Structural and biophysical analyses were performed to assess the effects of both amino acid substitutions on the KCTD15 protein.

RESULTS

A heterozygous c.310G>C variant encoding p.(Asp104His) within the BTB domain of KCTD15 was identified in an affected father and daughter and segregated with the phenotype. In the sporadically affected patient, a de novo heterozygous c.263G>A variant encoding p.(Gly88Asp) was present in KCTD15. Both substitutions were found to perturb the pentameric assembly of the BTB domain. A crystal structure of the BTB domain variant p.(Gly88Asp) revealed a closed hexameric assembly, whereas biophysical analyses showed that the p.(Asp104His) substitution resulted in a monomeric BTB domain likely to be partially unfolded at physiological temperatures.

CONCLUSION

BTB domain substitutions in KCTD1 and KCTD15 cause clinically overlapping phenotypes involving craniofacial abnormalities and cutis aplasia. The structural analyses demonstrate that missense substitutions act through a dominant negative mechanism by disrupting the higher order structure of the KCTD15 protein complex.

Preassembly of specific Gβγ subunits at GABAB receptors through auxiliary KCTD proteins accelerates channel gating

GABAB receptors (GBRs) are G protein-coupled receptors for GABA, the main inhibitory neurotransmitter in the brain. GBRs regulate fast synaptic transmission by gating Ca2+ and K+ channels via the Gβγ subunits of the activated G protein. It has been demonstrated that auxiliary GBR subunits, the KCTD proteins, shorten onset and rise time and increase desensitization of receptor-induced K+ currents. KCTD proteins increase desensitization of K+ currents by scavenging Gβγ from the channel, yet the mechanism responsible for the rapid activation of K+ currents has remained elusive. In this study, we demonstrate that KCTD proteins preassemble Gβγ at GBRs. The preassembly obviates the need for diffusion-limited G protein recruitment to the receptor, thereby accelerating G protein activation and, as a result, K+ channel activation. Preassembly of Gβγ at the receptor relies on the interaction of KCTD proteins with a loop protruding from the seven-bladed propeller of Gβ subunits. The binding site is shared between Gβ1 and Gβ2, limiting the interaction of KCTD proteins to these particular Gβ isoforms. Substituting residues in the KCTD binding site of Gβ1 with those from Gβ3 hinders the preassembly of Gβγ with GBRs, delays onset and prolongs rise time of receptor-activated K+ currents. The KCTD-Gβ interface, therefore, represents a target for pharmacological modulation of channel gating by GBRs.

Profiling the proximal proteome of the activated μ-opioid receptor

The μ-opioid receptor (μOR) represents an important target of therapeutic and abused drugs. So far, most understanding of μOR activity has focused on a subset of known signal transducers and regulatory molecules. Yet μOR signaling is coordinated by additional proteins in the interaction network of the activated receptor, which have largely remained invisible given the lack of technologies to interrogate these networks systematically. Here we describe a proteomics and computational approach to map the proximal proteome of the activated μOR and to extract subcellular location, trafficking and functional partners of G-protein-coupled receptor (GPCR) activity. We demonstrate that distinct opioid agonists exert differences in the μOR proximal proteome mediated by endocytosis and endosomal sorting. Moreover, we identify two new μOR network components, EYA4 and KCTD12, which are recruited on the basis of receptor-triggered G-protein activation and might form a previously unrecognized buffering system for G-protein activity broadly modulating cellular GPCR signaling.

KCTD7-related progressive myoclonic epilepsy: Report of 42 cases and review of literature

OBJECTIVE

KCTD7-related progressive myoclonic epilepsy (PME) is a rare autosomal-recessive disorder. This study aimed to describe the clinical details and genetic variants in a large international cohort.

METHODS

Families with molecularly confirmed diagnoses of KCTD7-related PME were identified through international collaboration. Furthermore, a systematic review was done to identify previously reported cases. Salient demographic, epilepsy, treatment, genetic testing, electroencephalographic (EEG), and imaging-related variables were collected and summarized.

RESULTS

Forty-two patients (36 families) were included. The median age at first seizure was 14 months (interquartile range = 11.75-22.5). Myoclonic seizures were frequently the first seizure type noted (n = 18, 43.9%). EEG and brain magnetic resonance imaging findings were variable. Many patients exhibited delayed development with subsequent progressive regression (n = 16, 38.1%). Twenty-one cases with genetic testing available (55%) had previously reported variants in KCTD7, and 17 cases (45%) had novel variants in KCTD7 gene. Six patients died in the cohort (age range = 1.5-21 years). The systematic review identified 23 eligible studies and further identified 59 previously reported cases of KCTD7-related disorders from the literature. The phenotype for the majority of the reported cases was consistent with a PME (n = 52, 88%). Other reported phenotypes in the literature included opsoclonus myoclonus ataxia syndrome (n = 2), myoclonus dystonia (n = 2), and neuronal ceroid lipofuscinosis (n = 3). Eight published cases died over time (14%, age range = 3-18 years).

SIGNIFICANCE

This study cohort and systematic review consolidated the phenotypic spectrum and natural history of KCTD7-related disorders. Early onset drug-resistant epilepsy, relentless neuroregression, and severe neurological sequalae were common. Better understanding of the natural history may help future clinical trials.

Genetics and Pathogenesis of Dystonia

Dystonia is a clinically and genetically highly heterogeneous neurological disorder characterized by abnormal movements and postures caused by involuntary sustained or intermittent muscle contractions. A number of groundbreaking genetic and molecular insights have recently been gained. While they enable genetic testing and counseling, their translation into new therapies is still limited. However, we are beginning to understand shared pathophysiological pathways and molecular mechanisms. It has become clear that dystonia results from a dysfunctional network involving the basal ganglia, cerebellum, thalamus, and cortex. On the molecular level, more than a handful of, often intertwined, pathways have been linked to pathogenic variants in dystonia genes, including gene transcription during neurodevelopment (e.g., KMT2B, THAP1), calcium homeostasis (e.g., ANO3, HPCA), striatal dopamine signaling (e.g., GNAL), endoplasmic reticulum stress response (e.g., EIF2AK2, PRKRA, TOR1A), autophagy (e.g., VPS16), and others. Thus, different forms of dystonia can be molecularly grouped, which may facilitate treatment development in the future.

DNA methylation at birth and lateral ventricular volume in childhood: a neuroimaging epigenetics study

BACKGROUND

Lateral ventricular volume (LVV) enlargement has been repeatedly linked to schizophrenia; yet, what biological factors shape LVV during early development remain unclear. DNA methylation (DNAm), an essential process for neurodevelopment that is altered in schizophrenia, is a key molecular system of interest.

METHODS

In this study, we conducted the first epigenome-wide association study of neonatal DNAm in cord blood with LVV in childhood (measured using T1-weighted brain scans at 10 years), based on data from a large population-based birth cohort, the Generation R Study (N = 840). Employing both probe-level and methylation profile score (MPS) approaches, we further examined whether epigenetic modifications identified at birth in cord blood are: (a) also observed cross-sectionally in childhood using peripheral blood DNAm at age of 10 years (Generation R, N = 370) and (b) prospectively associated with LVV measured in young adulthood in an all-male sample from the Avon Longitudinal Study of Parents and Children (ALSPAC, N = 114).

RESULTS

At birth, DNAm levels at four CpGs (annotated to potassium channel tetramerization domain containing 3, KCTD3; SHH signaling and ciliogenesis regulator, SDCCAG8; glutaredoxin, GLRX) prospectively associated with childhood LVV after genome-wide correction; these genes have been implicated in brain development and psychiatric traits including schizophrenia. An MPS capturing a broader epigenetic profile of LVV - but not individual top hits - showed significant cross-sectional associations with LVV in childhood in Generation R and prospectively associated with LVV in early adulthood within ALSPAC.

CONCLUSIONS

This study finds suggestive evidence that DNAm at birth prospectively associates with LVV at different life stages, albeit with small effect sizes. The prediction of MPS on LVV in a childhood sample and an independent male adult sample further underscores the stability and reproducibility of DNAm as a potential marker for LVV. Future studies with larger samples and comparable time points across development are needed to further elucidate how DNAm associates with this clinically relevant brain structure and risk for neuropsychiatric disorders, and what factors explain the identified DNAm profile of LVV at birth.

An approach for prioritizing candidate genes from RNA-seq using preclinical cocaine self-administration datasets as a test case

RNA-sequencing (RNA-seq) technology has led to a surge of neuroscience research using animal models to probe the complex molecular mechanisms underlying brain function and behavior, including substance use disorders. However, findings from rodent studies often fail to be translated into clinical treatments. Here, we developed a novel pipeline for narrowing candidate genes from preclinical studies by translational potential and demonstrated its utility in 2 RNA-seq studies of rodent self-administration. This pipeline uses evolutionary conservation and preferential expression of genes across brain tissues to prioritize candidate genes, increasing the translational utility of RNA-seq in model organisms. Initially, we demonstrate the utility of our prioritization pipeline using an uncorrected P-value. However, we found no differentially expressed genes in either dataset after correcting for multiple testing with false discovery rate (FDR < 0.05 or <0.1). This is likely due to low statistical power that is common across rodent behavioral studies, and, therefore, we additionally illustrate the use of our pipeline on a third dataset with differentially expressed genes corrected for multiple testing (FDR < 0.05). We also advocate for improved RNA-seq data collection, statistical testing, and metadata reporting that will bolster the field's ability to identify reliable candidate genes and improve the translational value of bioinformatics in rodent research.

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.

Customizable Open-Source Rotating Rod (Rotarod) Enables Robust Low-Cost Assessment of Motor Performance in Mice

Reliable measurements of motor learning and coordination in mice are fundamental aspects of neuroscience research. Despite the advent of deep-learning approaches for motor assessment, performance testing on a rotating rod (rotarod) has remained a staple in the neuroscientist's toolbox. Surprisingly, commercially available rotarod instruments offer limited experimental flexibility at a relatively high cost. In order to address these concerns, we engineered a highly-customizable, low-budget rotarod device with increased functionality. Here, we present a detailed guide to assemble this rotarod using simple materials. Our apparatus incorporates a variation of interchangeable rod sizes and designs which provides for adjustable testing sensitivity. Moreover, our rotarod is driven by open-source software enabling bespoke acceleration ramps and sequences. Finally, we report the strengths and weaknesses of each rod design following multiday testing on cohorts of C57BL/6 mice. We expect explorations in deviant rod types to provide a foundation for the development of increasingly sensitive models for motor performance testing along with low-budget alternatives for the research community.

Structural basis for the ubiquitination of G protein βγ subunits by KCTD5/Cullin3 E3 ligase

G protein-coupled receptor (GPCR) signaling is precisely controlled to avoid overstimulation that results in detrimental consequences. Gβγ signaling is negatively regulated by a Cullin3 (Cul3)-dependent E3 ligase, KCTD5, which triggers ubiquitination and degradation of free Gβγ. Here, we report the cryo-electron microscopy structures of the KCTD5-Gβγ fusion complex and the KCTD7-Cul3 complex. KCTD5 in pentameric form engages symmetrically with five copies of Gβγ through its C-terminal domain. The unique pentameric assembly of the KCTD5/Cul3 E3 ligase places the ubiquitin-conjugating enzyme (E2) and the modification sites of Gβγ in close proximity and allows simultaneous transfer of ubiquitin from E2 to five Gβγ subunits. Moreover, we show that ubiquitination of Gβγ by KCTD5 is important for fine-tuning cyclic adenosine 3´,5´-monophosphate signaling of GPCRs. Our studies provide unprecedented insights into mechanisms of substrate recognition by unusual pentameric E3 ligases and highlight the KCTD family as emerging regulators of GPCR signaling.

CRISPR/Cas9-Mediated Knockout of tnfaip1 in Zebrafish Plays a Role in Early Development

TNF α-induced protein 1 (TNFAIP1) was first identified in human umbilical vein endothelial cells and can be induced by tumor necrosis factor α (TNFα). Early studies have found that TNFAIP1 is involved in the development of many tumors and is closely associated with the neurological disorder Alzheimer's disease. However, little is known about the expression pattern of TNFAIP1 under physiological conditions and its function during embryonic development. In this study, we used zebrafish as a model to illustrate the early developmental expression pattern of tnfaip1 and its role in early development. First, we examined the expression pattern of tnfaip1 during early zebrafish development using quantitative real-time PCR and whole mount in situ hybridization and found that tnfaip1 was highly expressed in early embryonic development and, subsequently, expression became localized to anterior embryonic structures. To investigate the function of tnfaip1 during early development, we constructed a model of a stably inherited tnfaip1 mutant using the CRISPR/Cas9 system. Tnfaip1 mutant embryos showed significant developmental delays as well as microcephaly and microphthalmia. At the same time, we found decreased expression of the neuronal marker genes tuba1b, neurod1, and ccnd1 in tnfaip1 mutants. Analysis of transcriptome sequencing data revealed altered expression of the embryonic development related genes dhx40, hspa13, tnfrsf19, nppa, lrp2b, hspb9, clul1, zbtb47a, cryba1a, and adgrg4a in the tnfaip1 mutants. These findings suggest an important role for tnfaip1 in the early development of zebrafish.

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

G protein-coupled receptors (GPCRs) initiate an array of intracellular signaling programs by activating heterotrimeric G proteins (Gα and Gβγ 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 Gβγ. However, comprehensive details on the KCTD interaction with Gβγ remain unresolved. Here, we report that nearly all the 25 KCTD proteins interact with Gβγ. In this study, we screened Gβγ 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 Gβγ 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 Gβγ interaction, we uncovered that the KCTD17 C terminus is sufficient for Gβγ interaction. Finally, we demonstrated the functional consequence of the KCTD-Gβγ interaction by examining sensitization of the adenylyl cyclase-cAMP pathway in live cells. We found that Gβγ-mediated sensitization of adenylyl cyclase 5 was blunted by KCTD. We conclude that the KCTD family broadly engages Gβγ to shape GPCR signal transmission.

Non-canonical Golgi-compartmentalized Gβγ signaling: mechanisms, functions, and therapeutic targets

G protein Gβγ subunits are key mediators of G protein-coupled receptor (GPCR) signaling under physiological and pathological conditions; their inhibitors have been tested for the treatment of human disease. Conventional wisdom is that the Gβγ complex is activated and subsequently exerts its functions at the plasma membrane (PM). Recent studies have revealed non-canonical activation of Gβγ at intracellular organelles, where the Golgi apparatus is a major locale, via translocation or local activation. Golgi-localized Gβγ activates specific signaling cascades and regulates fundamental cell processes such as membrane trafficking, proliferation, and migration. More recent studies have shown that inhibiting Golgi-compartmentalized Gβγ signaling attenuates cardiomyocyte hypertrophy and prostate tumorigenesis, indicating new therapeutic targets. We review novel activation mechanisms and non-canonical functions of Gβγ at the Golgi, and discuss potential therapeutic interventions by targeting Golgi-biased Gβγ-directed signaling.