Abstract
We investigated the diurnal oscillation in abundance of the catalytic α subunit of the sodium/potassium pump (ATPα) in the brain of Drosophila melanogaster. This rhythm is bimodal and is particularly robust in the glia cells of the lamina, the first optic neuropil. We observed loss of ATPα cycling in lamina glia in behaviourally arrhythmic per01 and tim01 mutants and in flies overexpressing the pro-apoptotic gene hid in the PDF-positive clock neurons. Moreover, the rhythm of ATPα abundance was altered in cry01 and Pdf0 mutants, in flies with a weakened clock mechanism in retina photoreceptor cells and in those subject to downregulation of the neuropeptide ITP by RNAi. This complex, rhythmic regulation of the α subunit suggests that the sodium/potassium pump may be a key target of the circadian pacemaker to impose daily control on brain activities, such as rhythmic changes in neuronal plasticity, which are best observed in the visual system.
Highlights
In most organisms an endogenous circadian clock underpins daily rhythms in biochemistry, physiology and behavior
The lamina expresses the PIGMENT DISPERSING FACTOR (PDF) receptor [11] and is innervated by ION TRANSPORT PEPTIDE (ITP)-immunoreactive fibers originating from the 5th s-LNv [7] and we examined whether these two neuropeptides are involved in the cycling of a subunit of the sodium/potassium pump (ATPa)
We have described a complex regulation of the rhythm of abundance of ATPa measured as a cycle in the immunoreactivity of this protein in glial cells of the lamina
Summary
In most organisms an endogenous circadian clock underpins daily rhythms in biochemistry, physiology and behavior. The key steps are centered around the PER and TIM proteins, which inhibit their own transcription only after activation through extensive phosphorylation that targets them for degradation, resulting in a main rhythmic negative feedback loop to which others are interlocked [1]. Another fundamental property of the clock is entrainment to LD cycles, which is largely dependent upon CRY, a blue-light sensitive protein encoded by the cryptochrome (cry) gene. The receptor for ITP and its molecular functions are unknown
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