Wirak, G. S. | bioRxiv Science

bioRxiv2021

Age-associated changes to neuronal dynamics involve a loss of inhibitory signaling in C. elegans

In the aging brain, many of the alterations underlying cognitive and behavioral decline remain opaque. C. elegans offers a powerful model for aging research, with a simple, well-studied nervous system to further our understanding of the cellular modifications and functional alterations accompanying senescence. We perform multi-neuronal functional imaging across the aged C. elegans nervous system, measuring an age-associated breakdown in system-wide functional organization. At single-cell resolution, we detect shifts in activity dynamics toward higher frequencies. In addition, we measure a specific loss of inhibitory signaling that occurs early in the aging process and alters the systems critical excitatory/inhibitory balance. These effects are recapitulated with mutation of the calcium channel subunit UNC-2/CaV2. We find that manipulation of inhibitory GABA signaling can partially ameliorate or accelerate the effects of aging. The effects of aging are also partially mitigated by disruption of the insulin signaling pathway, known to increase longevity, or by a reduction of caspase activation. Data from mammals are consistent with our findings, suggesting a conserved shift in the balance of excitatory/inhibitory signaling with age that leads to breakdown in global neuronal dynamics and functional decline.

neuroscience↗

bioRxiv2020

Identification of palmitoyl protein thioesterase 1 substrates defines roles for synaptic depalmitoylation

Loss-of-function mutations in the depalmitoylating enzyme palmitoyl protein thioesterase 1 (PPT1) cause Neuronal Ceroid Lipofuscinosis type 1 (CLN1), a devastating neurodegenerative disease. Here, we provide a resource identifying PPT1 substrates. We utilized Acyl Resin-Assisted Capture and mass spectrometry to identify proteins with increased in vivo palmitoylation in PPT1 knockout mouse brains. We then validated putative substrates through direct depalmitoylation with recombinant PPT1. This stringent screen elucidated >100 novel PPT1 substrates at the synapse, including channels and transporters, G-protein-associated molecules, endo/exocytic components, synaptic adhesion molecules, and mitochondrial proteins. Cysteine depalmitoylation sites in transmembrane PPT1 substrates frequently participate in disulfide bonds in the mature protein. We confirmed that depalmitoylation regulates disulfide bond formation in a tertiary screen analyzing post-translational modifications. Collectively, the diverse PPT1 substrates highlight the role of PPT1 in mediating synapse functions, implicate molecular pathways in the etiology of CLN1, and advance our basic understanding of the purpose of depalmitoylation. HighlightsO_LI[~]10% of palmitoylated proteins are palmitoyl protein thioesterase 1 (PPT1) substrates C_LIO_LIUnbiased proteomic approaches identify 9 distinct classes of PPT1 substrates, including synaptic adhesion molecules and endocytic proteins C_LIO_LIProtein degradation does not require depalmitoylation by PPT1 C_LIO_LIDepalmitoylation mediates disulfide bond formation in transmembrane PPT1 substrates C_LI

neuroscience↗