Restoration of Cx43-ERp29 interactions rescues Amyloid-β induced gap junction deficits in human astrocytes

Astroglial dysfunction is increasingly recognized as a key contributor to Alzheimer’s disease (AD) pathology, complementing amyloid-β (Aβ) accumulation and neuronal impairment. Astrocytic networks rely on connexin 43 (Cx43)-based gap junctions to coordinate metabolic substrate sharing, calcium signalling, and neuroimmune responses that sustain neuronal and glial function. However, the mechanisms linking Aβ stress to Cx43 dysregulation and disrupted intercellular communication remain poorly understood. Using primary human cortical astrocytes, we show that prolonged Aβ exposure induces endoplasmic reticulum (ER) stress, which disrupts the interaction between Cx43 and the ER chaperone ERp29, leading to ER retention of Cx43 and a profound loss of functional gap-junctional coupling. Importantly, restoring ERp29 function, either through genetic upregulation of ERp29 or pharmacological alleviation of ER stress with 4-phenylbutyrate (4-PBA) rescues Cx43 trafficking to the plasma membrane and reinstates functional astroglial coupling. These findings identify the ERp29-Cx43 axis as a previously unrecognized mechanism regulating astrocytic Cx43 trafficking under Aβ-induced stress conditions. Schematic model illustrating Aβ-induced ER stress disrupting Cx43-ERp29 interaction, leading to ER retention of Cx43 and impaired gap junction intercellular communication (GJIC) in human astrocytes, which is rescued by ERp29 restoration or 4-Phenylbutyric acid (4-PBA) treatment.