Octopamine metabolically reprograms astrocytes to confer neuroprotection against a-synuclein

Octopamine is a well-established invertebrate neurotransmitter involved in fight-or-flight responses. In mammals, its function was replaced by norepinephrine. Nevertheless, it is present at trace amounts and can modulate the release of monoamine neurotransmitters by a yet unidentified mechanism. Here, through a multidisciplinary approach utilizing in vitro and in vivo models of a-synucleinopathy, we uncovered an unprecedented role for octopamine in driving the conversion from toxic to neuroprotective astrocytes in the cerebral cortex by fostering aerobic glycolysis. Neuron-derived octopamine acts on astrocytes via a TAAR1-Orai1-Ca2+-calcineurinmediated signaling pathway to stimulate lactate secretion. Lactate uptake in neurons via the MCT2-calcineurin-dependent pathway increases ATP and prevents neurodegeneration. Pathological increases of octopamine caused by a-synuclein halts lactate production in astrocytes and short-circuits the metabolic communication to neurons. Our work provides a novel function of octopamine as a modulator of astrocyte metabolism and hence neuroprotection with implications to a-synucleinopathies. Overall design: Comparative gene expression profiling analysis of RNA-seq data for rat primary neuronal cultures infected with either control or alpha synuclein-A53T variant and treated with either sub-saturating (0.2 µM) or saturating (2.0 µM) doses of FK506 or the vehicle control DMSO.