ZFIN ID: ZDB-PUB-090526-23
PHR regulates growth cone pausing at intermediate targets through microtubule disassembly
Hendricks, M., and Jesuthasan, S.
Date: 2009
Source: The Journal of neuroscience : the official journal of the Society for Neuroscience   29(20): 6593-6598 (Journal)
Registered Authors: Hendricks, Michael, Jesuthasan, Suresh
Keywords: none
MeSH Terms:
  • Animals
  • Anthracenes/pharmacology
  • Apoptosis Regulatory Proteins/genetics
  • Apoptosis Regulatory Proteins/metabolism
  • Calcium-Calmodulin-Dependent Protein Kinases/genetics
  • Calcium-Calmodulin-Dependent Protein Kinases/metabolism
  • Cells, Cultured
  • Death-Associated Protein Kinases
  • Dose-Response Relationship, Drug
  • Electroporation/methods
  • Enzyme Inhibitors/pharmacology
  • Gene Expression Regulation/drug effects
  • Gene Expression Regulation/physiology
  • Green Fluorescent Proteins/genetics
  • Growth Cones/drug effects
  • Growth Cones/physiology*
  • Imidazoles/pharmacology
  • MAP Kinase Kinase 4/genetics
  • MAP Kinase Kinase 4/metabolism
  • Membrane Proteins/genetics
  • Membrane Proteins/physiology*
  • Mice
  • Mice, Transgenic
  • Microtubules/metabolism*
  • Neurons/cytology*
  • Nocodazole/pharmacology
  • Paclitaxel/pharmacology
  • Phosphorylation/drug effects
  • Prosencephalon
  • Pyridines/pharmacology
  • Signal Transduction/drug effects
  • Signal Transduction/physiology
  • Spinal Cord/cytology
  • Tubulin Modulators/pharmacology
  • Zebrafish
  • Zebrafish Proteins/genetics
  • Zebrafish Proteins/metabolism
PubMed: 19458229 Full text @ J. Neurosci.
Axonal growth cones use intermediate targets to navigate in the developing nervous system. Encountering these sites is correlated with growth cone pausing. PHR (Phr1, Esrom, Highwire, RPM-1) is a large neuronal ubiquitin ligase that interacts with multiple signaling pathways. Mouse and zebrafish phr mutants have highly penetrant axon pathfinding defects at intermediate targets. Mouse phr mutants contain excessive microtubules in the growth cone, which has been attributed to upregulation of DLK/p38 signaling. Here, we ask whether this pathway and microtubule misregulation are indeed linked to guidance errors in the vertebrate brain, using the zebrafish. By live imaging, we show that loops form when microtubules retract without depolymerizing. JNK, but not p38, phosphorylation is increased in mutant growth cones. However microtubule looping cannot be suppressed by inhibiting JNK. The phr microtubule defect can be phenocopied by taxol, while microtubule destabilization in vitro using nocodazole prevents loop formation. Acute disruption in vivo with nocodazole suppresses the intermediate target guidance defect. Given that microtubule looping is associated with growth cone pausing, we propose that microtubule disassembly, mediated by PHR, is essential for exiting the paused state at intermediate targets.