Rho kinase activates ezrin-radixin-moesin (ERM) proteins and mediates their function in cortical neuron growth, morphology and motility in vitro.
The ezrin-radixin-moesin (ERM) family of proteins contribute to cytoskeletal processes underlying many vital cellular functions. Their previously elucidated roles in non-neuronal cells are an indication of their potential importance in CNS neurons. The specific mechanisms of their activation are unknown, but are likely to depend on factors such as the cell type and biological context. For ERM proteins to become active they must be phosphorylated at a specific C-terminal threonine residue. In non-neuronal cells, several kinases, including the Rho GTPase family member Rho kinase, have been identified as capable of phosphorylating the C-terminal threonine. In these experiments we have investigated specifically the potential role of Rho kinase mediated ERM activation in cortical neurons, utilizing a new pharmacologic inhibitor of Rho kinase and quantitative analysis of aspects of neuronal functions potentially mediated by ERM proteins. Rho kinase inhibition significantly suppressed aspects of neuronal development including neurite initiation and outgrowth, as well as growth cone morphology, with a concomitant loss of phosphorylated ERM immunolabeling in areas associated with neuronal growth. The ability of the Rho kinase inhibitor to decrease the amount of pERM protein was shown by immunoblotting. Post-injury responses were negatively affected by Rho kinase inhibition, namely by a significant decrease in the number of regenerative neurites. We investigated a novel role for ERM proteins in neuron migration using a post-injury motility assay, where Rho kinase inhibition resulted in significant and drastic reduction in neuron motility and phosphorylated ERM immunolabeling. Thus, Rho kinase is an important activator of ERMs in mediating specific neuronal functions.
Haas
Matilda A
MA
NeuroRepair Group, University of Tasmania, Hobart, Australia.
Vickers
James C
JC
Dickson
Tracey C
TC
D000818:Animals; D001369:Axons / Q000187:drug effects; D015153:Blotting, Western / Q000379:methods; D049108:Cell Enlargement / Q000187:drug effects; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology*; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D004622:Embryo, Mammalian; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007150:Immunohistochemistry / Q000379:methods; D047908:Intracellular Signaling Peptides and Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009447:Neuroblastoma; D009474:Neurons / Q000166:cytology* / Q000187:drug effects; D010750:Phosphoproteins / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D011554:Pseudopodia / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism*; D014404:Tubulin / Q000378:metabolism; D054460:rho-Associated Kinases
D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; C513243:Etv5 protein, rat; D047908:Intracellular Signaling Peptides and Proteins; C489787:MAP2 protein, rat; D008869:Microtubule-Associated Proteins; D010750:Phosphoproteins; D014157:Transcription Factors; D014404:Tubulin; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases