ERBB4 colocalizes with phosphorylated tau aggregates in multiple tauopathies.

The neuregulin-ERBB4 pathway is essential for maintaining cellular function. Upon stimulation by its ligand, neuregulin, ERBB4-a receptor tyrosine kinase-triggers multiple cellular responses, including proliferation, apoptosis, differentiation, and neuromuscular junction formation. Previous research has implicated dysregulated ERBB4 signaling in the pathophysiology of several neurodegenerative disorders, such as Alzheimer's disease, progressive supranuclear palsy, amyotrophic lateral sclerosis, and Parkinson's disease. In this study, we examined ERBB4 expression in diseases characterized by phosphorylated tau (MAPT) pathology. We found that ERBB4 colocalized with neuronal and glial phosphorylated tau-positive inclusions in multiple tauopathies, including Pick's disease, Alzheimer's disease, corticobasal degeneration, progressive supranuclear palsy, argyrophilic grain disease, and frontotemporal lobar degeneration with MAPT mutation. Conversely, ERBB4 did not colocalize with α-synuclein aggregates in α-synucleinopathies (Parkinson's disease and multiple system atrophy) or with neuronal intranuclear inclusions in triplet repeat disorders (Huntington's disease and dentatorubral-pallidoluysian atrophy). A co-immunoprecipitation assay indicated that ERBB4 can interact with tau intracellularly. Notably, in corticobasal degeneration, we observed ectopic ERBB4 expression in astrocytes lacking apparent phosphorylated tau aggregates. These findings suggest a potential role for ERBB4 in the pathophysiology of tau-related neurodegenerative diseases.