Biology subjects

Pippadpally, S.

Publications and source records attributed to Pippadpally, S..

3 recordsLinked to original sources

bioRxiv2025

Pathogenic mutations in Clathrin Heavy Chain associated with intellectual disability impair synaptic architecture and learning in Drosophila

Clathrin-mediated endocytosis is essential for neural development and function. Recent studies have linked de novo mutations in the clathrin heavy chain (Chc) gene to a range of neurodevelopmental disorders. In this study we have modelled two pathogenic mutations: L1047P and W1108R in Drosophila melanogaster and examined their effects on vesicle dynamics, ligand uptake, neuronal development and memory formation. Our data shows that expression of these mutant forms of Chc result in reduced survival and defective learning when expressed ubiquitously or exclusively in neurons. Our analysis also reveals that these mutations have the ability to disrupt vesicle dynamics and reduce ligand uptake in cells. Although we do not see a defect in neuronal morphology and function at the larval neuro-muscular junction, we see an increase in the number of Dlg-negative boutons, and a significant reduction in Spectrin expression, indicative of disruptions in the process of synapse maturation. Overall, this study provides mechanistic insights into the cellular and molecular basis of Chc-related neurodevelopmental disorders.

cell biology↗

bioRxiv2024

Endocytosis restricts synapse growth by attenuating Highwire/PHR1-dependent JNK signaling in a pathway parallel to the BMP signaling

Synaptic growth and organization are orchestrated by pre - and post-synaptic signaling, neuronal activity, and environmental cues. Although endocytosis is known to attenuate synaptic growth, the underlying signaling mechanisms have remained elusive. Here, we uncover a previously unrecognized mechanism by which endocytosis constrains synaptic growth through regulation of the neuronal E3 ubiquitin ligase Highwire (Hiw/Phr1). We show that loss of endocytosis causes Hiw to accumulate in neuronal cell bodies, leading to elevated MAP3K Wallenda (Wnd)/DLK levels and hyperactivation of JNK signaling. The accumulated Hiw assembles into dynamic liquid-liquid phase-separated condensates, as revealed by their rapid and reversible dissolution with 1,6-hexanediol. Acute blockade of endocytosis using a temperature-sensitive dynamin mutant Shibiretssimilarly triggered robust Hiw phase separation. We further demonstrate that Rab11-positive recycling endosomes are essential for proper Hiw localization and turnover, directly linking endosomal trafficking to the control of JNK signaling. Finally, we show that both BMP and JNK signaling are necessary and sufficient to guide synaptic morphogenesis at the Drosophila NMJ, thereby integrating endocytic trafficking with synaptic growth signaling. Our findings establish endocytosis as a critical regulator of Hiw/Phr1-dependent JNK signaling via liquid-liquid phase separation, with implications that extend beyond synaptic morphogenesis to axon injury and degeneration pathways.

neuroscience↗

bioRxiv2024

Prefoldin 5 is a microtubule-associated protein that suppresses Tau-aggregation and neurotoxicity

Tauopathies represent a major class of neurodegenerative disorders associated with intracellular aggregates of the microtubule-associated protein Tau. To identify molecular modulators of Tau toxicity, we used a genetic screen to identify protein chaperones whose RNAi-mediated knockdown could modulate hTauV337M-induced eye-ommatidial degeneration in Drosophila. This screen identified the Prefoldins Pfdn5 and Pfdn6 as strong modifiers of hTauV337M cytotoxicity. Consistent with the known function of Pfdn as a cotranslational chaperone for tubulin, Pfdn5 mutants showed substantially reduced levels of tubulin monomer. However, additional microtubule-related functions were indicated by the robust unexpected association of Pfdn5 with axonal microtubules in vivo, as well as binding with stabilized microtubules in biochemical assays. Loss of Pfdn5 resulted in neuromuscular junctions (NMJ) defects similar to those previously described in hTau-expressing flies: namely, increased supernumerary boutons and fewer microtubule loops within mature presynaptic boutons. Significantly, synaptic phenotypes caused by hTauV337M overexpression were also strongly enhanced in a Pfdn5 mutant background. Consistent with a role in modulating Tau toxicity, not only did loss of Pfdn5 result in increased accumulations of Tau-aggregates in hTauV337M expressing neurons, but also neuronal overexpression of Prefoldin strikingly ameliorated age-dependent neurodegeneration and memory deficits induced by pathological hTau. Together, these and other observations described herein: (a) provide new insight into Prefoldin-microtubule interactions; (b) point to essential posttranslational roles for Pfdn5 in controlling Tau-toxicity in vivo; and (c) demonstrate that Pfdn5 overexpression is sufficient to restrict Tau-induced neurodegeneration.

neuroscience↗