BRSK1

BRSK1, also named SAD-B, is a brain-specific serine/threonine kinase of the AMPK-related family, activated when LKB1 phosphorylates its activation-loop threonine. BRSK1 phosphorylates tau at serine 262 and 356, priming sites that detach tau from microtubules and relevant to Alzheimer disease pathology. It also orchestrates neuronal polarity: mouse mutants lacking both mammalian BRSK kinases fail to specify axons, while BRSK-dependent phosphorylation of microtubule-associated proteins organizes the developing cytoskeleton, and studies in Caenorhabditis elegans established the ancestral role of SAD kinases in establishing neuronal polarity and presynaptic differentiation. These functions make BRSK1 a key link between metabolic signaling and neural circuit assembly.