Biology subjects

Tutas, J.

Publications and source records attributed to Tutas, J..

4 recordsLinked to original sources

bioRxiv2024

Endocytic adaptor AP-2 maintains Purkinje cell function by balancing cerebellar parallel and climbing fiber synapses

The selective loss of cerebellar Purkinje cells is a hallmark of various neurodegenerative movement disorders, yet the precise mechanism driving their degeneration remains enigmatic. Here, we show that the endocytic adaptor protein complex 2 (AP-2) is essential for the survival of Purkinje cells. Employing a multidisciplinary approach encompassing mouse genetics, viral tracing, ex vivo calcium imaging, and kinematic analysis, we demonstrate that mice lacking the {micro}-subunit of AP-2 in cerebellar Purkinje cells exhibit early-onset ataxia associated with progressive Purkinje cell degeneration. Importantly, we uncover that synaptic input dysfunctions, characterized by a predominance of parallel fiber (PF) over climbing fiber (CF) synapses, precede Purkinje cell loss. Mechanistically, we find that AP-2 localizes to Purkinje cell dendrites, where it interacts with the PF synapse-enriched protein GRID2IP. The loss of AP-2 results in proteasome-dependent degradation of GRID2IP and accumulation of the glutamate {delta}2 receptor (GLUR{delta}2) in distal Purkinje cell dendrites, leading to an excess of PF synapses while CF synapses are drastically reduced. The overrepresentation of PF synaptic input induces Purkinje cell hyperexcitation, which can be alleviated by enhancing synaptic glutamate clearance using the antibiotic ceftriaxone. Our findings demonstrate the critical role of AP-2 in preventing motor gait dysfunctions by regulating GRID2IP levels in Purkinje cells, thereby preserving the equilibrium of PF and CF synaptic inputs in a cell-autonomous manner.

neuroscience↗

bioRxiv2024

Autophagy regulator ATG5 preserves cerebellar function by safeguarding its glycolytic activity

Dysfunctions in autophagy, a highly conserved cellular mechanism responsible for the degradation of intracellular components within lysosomes, often result in neurodegeneration. The neuroprotective effect of autophagy varies across neuronal subtypes, and the mechanisms of selective vulnerability of neurons to autophagy dysfunction are currently unknown. Utilizing a mouse model of ATG5 deficiency in inhibitory neurons and a comprehensive approach, including PET imaging, metabolomics, stable-isotope labeling studies, and live cell imaging, we establish that autophagy contributes to the survival of cerebellar Purkinje cells (PCs) by safeguarding their glycolytic activity. We show that the core autophagy protein ATG5 downregulates the levels of the glucose transporter 2 (GLUT2) during brain maturation. Autophagy-deficient PCs exhibit increased glucose uptake, along with elevated levels of glycolytic intermediates and methylglyoxal-modified proteins. We propose lysophosphatidic acid and serine as glycolytic intermediates inducing PC death and demonstrate that deletion of GLUT2 in ATG5-deficient mice mitigates PC neurodegeneration and restores their ataxic gait. Taken together, this study reveals a novel neuroprotective role of autophagy in preventing excessive glycolytic metabolism in the brain.

neuroscience↗

bioRxiv2022

Autophagy regulates neuronal excitability by controlling cAMP/Protein Kinase A signaling

Autophagy provides nutrients during starvation and eliminates detrimental cellular components. However, accumulating evidence indicates that autophagy is not merely a housekeeping process. Here, we show that the protein AuTophaGy 5 (ATG5) functions in neurons to regulate the cAMP-dependent protein kinase A (PKA)-mediated phosphorylation of a synapse-confined proteome. This function of ATG5 is independent of bulk turnover of synaptic proteins and requires the targeting of PKA inhibitory R1 subunits to autophagosomes. Neuronal loss of ATG5 causes synaptic accumulation of PKA R1, which sequesters the PKA catalytic subunit and diminishes the cAMP/PKA-dependent phosphorylation of postsynaptic cytoskeletal proteins mediating AMPAR trafficking. Glutamatergic neurons-confined ATG5 deletion augments AMPAR-dependent excitatory neurotransmission and causes the appearance of spontaneous recurrent seizures in mice. Our findings identify a novel role of autophagy in regulating PKA signaling at glutamatergic synapses and suggest the PKA as a target for restoration of synaptic function in neurodegenerative conditions with autophagy dysfunction.

neuroscience↗

bioRxiv2017

Artificial anion-conducting channelrhodopsins with tuned spectra, modified kinetics and enhanced light sensitivity

Genetic engineering of natural light-gated ion channels has proven a powerful way to generate optogenetic tools for a wide variety of applications. In recent years, blue light-activated engineered anion conducting channelrhodopsins (eACRs) have been developed, improved, and were successfully applied in vivo. We asked whether the approaches used to create eACRs can be transferred to other well-characterized cation-conducting channelrhodopsins (CCRs) to obtain eACRs with a broad spectrum of biophysical properties. We generated 22 variants using two conversion strategies applied to 11 CCRs and screened them for membrane expression, photocurrents and anion selectivity. We obtained two novel eACRs, Phobos and Aurora, with blue-and red-shifted action spectra and photocurrents similar to existing eACRs. Furthermore, step-function mutations greatly enhanced the cellular operational light sensitivity due to a slowed-down photocycle. These bistable eACRs can be reversibly toggled between open and closed states with brief light pulses of different wavelengths. All new eACRs reliably inhibited action potential firing in pyramidal CA1 neurons. In Drosophila larvae, eACRs conveyed robust and specific light-dependent inhibition of locomotion and nociception.

neuroscience↗