Recruitment of Neuronal KCNQ2/3 Channels to Membrane Microdomains Depends on Palmitoylation of Alzheimer's Disease-Related Protein BACE1

{beta}-secretase 1 ({beta}-site amyloid precursor protein (APP)-cleaving enzyme 1, BACE1) plays a crucial role in the amyloidogenesis of Alzheimers Disease (AD). BACE1 was also discovered to act like an auxiliary subunit to modulate neuronal KCNQ2/3 channels independent of its proteolytic function. BACE1 is palmitoylated at its carboxyl-terminal region, which brings BACE1 to ordered, cholesterol-rich membrane microdomains (rafts). However, the physiological consequences of this specific localization of BACE1 remain elusive. Using spectral Forster Resonance Energy Transfer (FRET), we confirmed BACE1 and KCNQ2/3 channels formed a signaling complex, a phenomenon that was relatively unaffected by the palmitoylation of BACE1. Nevertheless, palmitoylation of BACE1 was required for the recruitment of KCNQ2/3 channels to lipid-raft domains. Mutating the four carboxyl-terminal cysteines (4C/A) of BACE1 abolished the BACE1-dependent increase of FRET between KCNQ2/3 and a lipid raft-specific protein Caveolin1. Furthermore, we used two fluorescent probes, named L10 and S15, to label lipid rafts and non-raft domains of the plasma membrane respectively. Coexpressing BACE1 substantially elevated the FRET between L10 and KCNQ2/3 whereas BACE1-4C/A failed to produce this effect. In contrast, BACE1 had no significant effect on the FRET between S15 probes and KCNQ2/3 channels. In addition, the reduction of BACE1-dependent FRET between raft-targeting L10 probes and KCNQ2/3 channels by applying cholesterol-extracting reagent methyl-{beta}-cyclodextrin (M{beta}CD), raft-disrupting general anesthetics, and pharmacological inhibitors of palmitoylation all supported our hypothesis of the palmitoylation-dependent and raft-specific localization of KCNQ2/3 channels. Collectively, we provide a mechanism underlying how the localization of a neuronal potassium channel is controlled by AD-related protein BACE1. SIGNIFICANCE STATEMENTAlzheimers disease (AD) has no effective cure. Animals with knockout of the key related enzyme BACE1 do not generate {beta}-amyloids or develop AD, but rather exhibit altered behaviors and neuronal deficits. A new linkage between BACE1 and neuronal excitability is the interaction between BACE1 and KCNQ channels. KCNQ channels function as a brake for excessive neuronal excitabilities and are modulated by interacting with BACE1. We revealed a mechanism that BACE1 helps to recruit KCNQ channels to membrane microdomains called rafts. This localization of KCNQ channels is dependent on a specific type of lipidation of BACE1. This mechanism advances our understanding of AD pathophysiology and could potentially provide therapeutic interventions when rescuing the neuronal abnormalities after ablating BACE1 genetically is needed.