Biology subjects

Thakur, R. S.

Publications and source records attributed to Thakur, R. S..

2 recordsLinked to original sources

bioRxiv2023

PDZD8 promotes autophagy at ER-Lysosome contact sites to regulate synaptogenesis

Building synaptic connections, which are often far from the soma, requires coordinating a host of cellular activities from transcription to protein turnover, placing a high demand on intracellular communication. Membrane contact sites (MCSs) formed between cellular organelles have emerged as key signaling hubs for coordinating an array of cellular activities. We have found that the endoplasmic reticulum (ER) MCS tethering protein PDZD8 is required for activity-dependent synaptogenesis. PDZD8 is sufficient to drive ectopic synaptic bouton formation through an autophagy-dependent mechanism and required for basal synapse formation when autophagy biogenesis is limited. PDZD8 functions at ER-late endosome/lysosome (LEL) MCSs to promote lysosome maturation and accelerate autophagic flux. Mutational analysis of PDZD8s SMP domain further suggests a role for lipid transfer at ER-LEL MCSs. We propose that PDZD8-dependent lipid transfer from ER to LELs promotes lysosome maturation to increase autophagic flux during periods of high demand, including activity-dependent synapse formation. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=170 SRC="FIGDIR/small/564828v2_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@1c6b752org.highwire.dtl.DTLVardef@12d77c3org.highwire.dtl.DTLVardef@11d50corg.highwire.dtl.DTLVardef@ba404f_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2022

Expanded tRNA methyltransferase family member TRMT9B regulates synaptic growth and function

Nervous system function relies on the formation and function of synaptic connections between neurons. Through a genetic screen in Drosophila for new conserved synaptic genes, we identified CG42261/Fid/ TRMT9B as a negative regulator of synaptogenesis. TRMT9B has been studied for its role as a tumor suppressor in multiple carcinomas and is one of two metazoan homologs of yeast tRNA methyltransferase 9 (Trm9), which methylates tRNA wobble uridines. Members of the expanded family of tRNA methyltransferases are increasingly being associated with neurological disorders and new biochemical functions. Interestingly, whereas Trm9 homolog ALKBH8/CG17807 is ubiquitously expressed, we find that TRMT9B is enriched in the nervous system, including at synapses. However, in the absence of animal models the role of TRMT9B in the nervous system has remained unknown. Here, we generated null alleles of TRMT9B and ALKBH8, and through liquid chromatography-mass spectrometry find that ALKBH8 is responsible for canonical tRNA wobble uridine methylation under basal conditions. In the nervous system, we find that TRMT9B negatively regulates synaptogenesis through a methyltransferase-dependent mechanism in agreement with our modeling studies. Finally, we find that neurotransmitter release is impaired in TRMT9B mutants. Our findings reveal a role for TRMT9B in regulating synapse formation and function, and highlight the importance of the expanded family of tRNA methyltransferases in the nervous system.

neuroscience↗