Abstract
Small molecule polyamines are abundant in all life forms and participate in diverse aspects of cell growth and differentiation. Spermidine/spermine acetyltransferase (SAT1) is the rate-limiting enzyme in polyamine catabolism and a primary genetic risk factor for suicidality. Here, using genome-wide screening, we find that SAT1 selectively controls nicotinic acetylcholine receptor (nAChR) biogenesis. SAT1 specifically augments assembly of nAChRs containing α7 or α4β2, but not α6 subunits. Polyamines are classically studied as regulators of ion channel gating that engage the nAChR channel pore. In contrast, we find polyamine effects on assembly involve the nAChR cytosolic loop. Neurological studies link brain polyamines with neurodegenerative conditions. Our pharmacological and transgenic animal studies find that reducing polyamines enhances cortical neuron nAChR expression and augments nicotine-mediated neuroprotection. Taken together, we describe a most unexpected role for polyamines in regulating ion channel assembly, which provides a new avenue for nAChR neuropharmacology.
Highlights
Small molecule polyamines are abundant in all life forms and participate in diverse aspects of cell growth and differentiation
Transfected cells were stimulated with nicotine (100 μM) and intracellular Ca2+ was quantified with a fluorescence imaging plate reader (FLIPR) (Fig. 1a)
We evaluated the effect of SAT1 on other nicotinic acetylcholine receptor (nAChR) and other Cys-loop receptors both by FLIPR and electrophysiology
Summary
Small molecule polyamines are abundant in all life forms and participate in diverse aspects of cell growth and differentiation. Like SAT1 co-transfection, DFMO pretreatment augmented surface expression of α4β2 and synergized with NACHO to further enhance α4β2 and α7 surface receptors (Fig. 2a, b). We find that polyamines, independent of their established role in ion channel gating, enhance nAChR function by promoting surface expression and augmenting receptor assembly.
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