KLHL9 (kelch like family member 9) functions as a substrate-specific adapter protein in BCR (BTB-CUL3-RBX1) E3 ubiquitin-protein ligase complexes with diverse cellular roles. The protein forms complexes with KLHL13 and CUL3 to regulate multiple cellular processes through targeted protein ubiquitination 1. In mitotic regulation, KLHL9 mediates ubiquitination of AURKB, controlling its dynamic behavior on mitotic chr9 and coordinating faithful mitotic progression and cytokinesis completion. The KLHL9-KLHL13-CUL3 complex also regulates mTORC1 signaling by ubiquitinating Rheb at the lysosome, supporting amino acid-induced mTORC1 activation 2. Additionally, this complex targets IRS1 for proteasomal degradation, linking autophagy deficiency to insulin resistance 3. KLHL9 plays roles in host-pathogen interactions, where bacterial pathogens like Burkholderia pseudomallei hijack the KLHL9-KLHL13-CUL3 complex to promote mitophagy through IMMT ubiquitination, facilitating pathogen survival 14. The complex is also required for interferon-γ-induced immunity against intracellular pathogens 5. Clinically, KLHL9 deletions are found in over 50% of mesenchymal glioblastoma cases and correlate with poor survival across multiple cancer types 67.