Biology subjects

Overhoff, M.

Publications and source records attributed to Overhoff, M..

3 recordsLinked to original sources

bioRxiv2025

Nutrient stress activates Rab5b-mediated autophagy to remodel the synaptic proteome

Synaptic proteostasis is crucial for maintaining neuronal function and plasticity, yet how synapses adapt to metabolic stress remains poorly understood. Here, we show that nutrient deprivation, particularly serum withdrawal, induces robust autophagy-dependent remodeling of the synaptic proteome, while mTORC1 inhibition has more limited effects. Nutrient stress rapidly activates autophagy both globally and at synapses, with synaptic autophagy peaking within 1-2 hours of serum withdrawal. Mechanistically, we uncover that the LC3 lipidation complex (ATG5-ATG12-ATG16L1) is recruited to synapses via Rab5b-positive endosomes in a dynein-dependent manner. Live imaging reveals enhanced Rab5b-ATG16L1 co-trafficking and increased ATG5 mobility upon serum withdrawal, supporting a model of spatiotemporally controlled autophagy precursor delivery to synaptic compartments. Functionally, nutrient deprivation acutely dampens neuronal excitability in vitro, while a two-week fasting-mimicking diet in vivo triggers synaptic proteome remodeling that overlaps with starvation-induced autophagy cargo. In contrast, restriction of mTORC1-activating amino acids fails to induce comparable synaptic changes, suggesting that synaptic autophagy is regulated by nutrient signals beyond mTORC1. Our findings define a Rab5b-mediated trafficking mechanism that couples nutrient sensing to localized synaptic degradation, providing new insight into how neurons preserve proteostasis under metabolic challenge.

neuroscience↗

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↗

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↗