GJA1 (connexin43) has been predicted as the top key driver of an astrocyte enriched subnetwork associated with Alzheimer's disease (AD). In this study, we comprehensively examined GJA1 expression across 29 transcriptomic and proteomic datasets from post-mortem AD and normal control brains. We demonstrated that GJA1 was strongly associated with AD amyloid and tau pathologies and cognitive functions. RNA sequencing analysis of Gja1-/- astrocytes validated that Gja1 regulated the subnetwork identified in AD, and many genes involved in A? metabolism. Astrocytes lacking Gja1 showed reduced Apoe protein levels as well as impaired A? phagocytosis. Consistent with this, wildtype neurons co-cultured with Gja1-/- astrocytes contained higher levels of A? species than those with wildtype astrocytes. Moreover, Gja1-/- astrocytes was more neuroprotective under A? stress. Our results underscore the importance of GJA1 in AD pathogenesis and its potential for further investigation as a promising pharmacological target in AD.