TBCK (TBC1 domain containing kinase) is a protein kinase that plays critical roles in neuronal function through multiple cellular mechanisms. TBCK is a component of the FERRY complex, which mediates endosomal transport of specific mRNAs by directly interacting with mRNAs and RAB5A, recruiting mRNAs and ribosomes to early endosomes 1. In neurons, TBCK preferentially localizes to endolysosomal vesicles and colocalizes with mRNA in lysosomes, facilitating mRNA transport to axonal compartments 2. Loss of TBCK leads to compartment-specific mRNA trafficking defects and lysosomal axonal retrograde trafficking defects due to reduced JIP4 levels 2. TBCK also regulates mitochondrial dynamics and membrane potential, with knockdown causing mitochondrial dysfunction that can be partially rescued by mitochondrial fission inhibitors 3. Biallelic loss-of-function mutations in TBCK cause TBCK-related encephalopathy, a rare pediatric neurodegenerative disorder characterized by hypotonia, intellectual disability, epilepsy, and hypoventilation requiring respiratory support 4. Even heterozygous TBCK variants may cause mild neurologic symptoms, including peripheral neuropathy manifestations such as acquired toe and foot deformities 5. The protein's essential role in mRNA localization and mitochondrial health makes it critical for neuronal survival and function.