Voltage-dependent sodium channel complexes consist of a pore-forming and voltage-sensing α-subunit and one or two β-subunits. The latter are type I transmembrane proteins with a broad spectrum of functions in channel expression and surface targeting, in channel electrophysiology and, notably, in cell-adhesion of excitable and non-excitable cells. Like the amyloid-precursor protein (APP), β-subunits are substrates for sequential cleavage either by α- and γ-secretase, or by β- and γ-secretase. Here, we focus on the processing of β-subunits by the amyloidogenic β-secretase, BACE1, which is up-regulated in Alzheimer's disease and is considered a highly promising pharmacologic target. Based on data from BACE1-deficient or over-expressing mice and from heterologous expression systems, this review summarizes our growing understanding of how BACE1-mediated cleavage of β-subunits interferes with their multiple physiological functions.