Microtubule-associated protein tau (phosphorylated at Serine 396) (pS396-tau)

Microtubule-associated protein tau (MAPT) is a major microtubule-stabilizing protein found predominantly in the axons of neurons [1]. In its physiological state, tau regulates the stability of axonal microtubules, which are essential for intracellular transport and structural integrity [1]. However, in neurodegenerative diseases known as tauopathies, tau becomes hyperphosphorylated at various sites, including Serine 396 (S396) [2]. Phosphorylation at S396 is a hallmark of pathological tau; it reduces the protein's affinity for microtubules, leading to cytoskeletal instability and the formation of paired helical filaments (PHFs) [2]. These filaments eventually aggregate into neurofibrillary tangles (NFTs), which are strongly correlated with cognitive decline in Alzheimer's disease [2]. Therapeutic interventions targeting pS396-tau include active and passive immunotherapies, such as the vaccine ACI-35, which are designed to elicit an immune response against this specific phospho-epitope to clear toxic tau species [3, 4]. Additionally, small molecule inhibitors targeting kinases like Glycogen Synthase Kinase 3 beta (GSK-3β) aim to prevent the phosphorylation of tau at this site [5]. Targeting specific phosphorylated residues like S396 is intended to provide a more precise therapeutic approach, sparing the functional, non-phosphorylated tau required for normal neuronal health [3].

Other names

MAPTTau proteinp-tau396pS396-tauPhospho-tau (Ser396)Neurofibrillary tangle proteinPHF-tau

The mechanism of action involves the use of active or passive immunotherapy to target and clear tau species phosphorylated at Serine 396, thereby preventing the formation of neurotoxic aggregates and the spread of tau pathology [3, 4]. Alternatively, small molecule inhibitors target upstream kinases, such as GSK-3β, to reduce the phosphorylation of tau at this specific residue [5].