KCTD2 (potassium channel tetramerization domain containing 2) is a substrate adaptor for the CUL3-RING E3 ubiquitin ligase complex that regulates heterotrimeric G-protein signaling and cellular growth. KCTD2 associates with CUL3 and promotes monoubiquitination of Gβ subunits in response to G-protein activation, modulating downstream effector signaling 1. The protein exhibits functional redundancy with related family members KCTD5 and KCTD17; progressive knockout of all three KCTD isoforms most severely impairs cell proliferation and survival 2. KCTD2 orthologs are functionally conserved with Drosophila Insomniac and can substitute for this protein in regulating sleep and synaptic function through CUL3-dependent ubiquitination pathways 3. Clinically, KCTD2 has emerged as a tumor suppressor in glioblastoma; decreased KCTD2 expression in glioma stem cells promotes self-renewal and tumor growth by failing to ubiquitinate and degrade c-Myc 4. Patients with low KCTD2 mRNA coupled with high c-Myc signature show poor prognosis. A GWAS identified the ATP5H/KCTD2 locus as associated with Alzheimer disease risk, implicating the gene in mitochondrial energy production and neuronal stress responses 5. Recent unbiased screening in mice uncovered KCTD2 among previously unrecognized genes associated with cardiac abnormalities 6. These disease associations suggest KCTD2 dysfunction impacts multiple organ systems through disrupted ubiquitin-dependent protein regulation.