The present invention discloses a dysregulation of the KCNN3 gene and the protein products thereof in Alzheimer's disease patients and individuals being at risk of developing Alzheimer's disease. Based on this finding, the invention provides methods for diagnosing and prognosticating Alzheimer's disease in a subject, and for determining whether a subject is at increased risk of developing Alzheimer's disease. Furthermore, this invention provides therapeutic and prophylactic methods for treating and preventing Alzheimer's disease and related neurodegenerative disorders using the KCNN3 gene and its corresponding gene products. Screening methods for modulating agents of neurodegenerative diseases are also disclosed.