Landowski, LM and Gasperini, RJ and Taylor, BVM and West, AK and Foa, LC, Metallothionein I/II induces growth cone chemotaxis via an LRP 1 and LRP 2 dependent mechanism, Neuroscience 2012, 13-17 October, 2012, New Orleans, Louisiana (2012) [Conference Extract]
Introduction: Axon guidance is essential in the developing nervous system as well as in regeneration and reinnervation of target tissues after neuronal injury. It is likely that both traditional and novel receptorligand systems are necessary to guide axon growth cones post nerve injury. We examined a novel guidance cuereceptor mechanism: metallothionein I/II (MTI/II) chemoattraction, mediated via the lipoprotein receptorrelated proteins 1 and 2 (LRP1 and LRP2).
Methods: The turning response of growth cones from embryonic (E1618) rat dorsal root ganglia were measured in vitro, using the growth cone turning assay 1 . Immunohistochemistry and western blotting were used to quantify protein levels in control and knockdown cultures.
Results: Immunocytostaining established that LRP1 and LRP2 are found at the leading edge and on filopodia, suggesting that they are part of the environmentsensing machinery of growth cones. We tested a range of LRP ligands for chemotactic properties using the growth cone turning assay, including MTI/II, ApoE3, tissue plasminogen activator, alpha2 macroglobulin and transthyretin. The only LRP ligands tested that elicited a turning response in growth cones were MTI/II and MTIII. Growth cones were attracted to MTI/II (turning angle 9.8°±1.7°, n=11, p<0.0001, compared to control 1.8° ± 1.1°). Interestingly, the structurally related MTIII protein induced robust growth cone repulsion (13.8°±1.9°, n=14, p<0.0001). Growth cone turning towards a gradient of MTI/II was abolished by LRPreceptor inhibition with receptor associated protein (RAP, 0.6°± 1.2) and siRNA knockdown of LRP1 (3.5° ± 1.9) or LRP2 (3.6° ± 2.5). This data demonstrates that both LRP1 and LRP2 are necessary for MTI/IImediated chemotactic signal transduction. MTI/IImediated chemotaxis was found to be dependent on calcium ion concentration, removal of extracellular calcium abolished chemoattraction. Furthermore, pharmacological inhibition of calcium/calmodulindependent kinase II suggests that LRP1 and LRP2 signal via established downstream effectors. The LRPMTI/II chemotactic system represents a novel, nonclassical axon guidance system that may be exploited in repairing the injured nervous system.
|Item Type:||Conference Extract|
|Keywords:||regeneration, peripheral nervous system, axon guidance|
|Research Division:||Medical and Health Sciences|
|Research Field:||Peripheral Nervous System|
|Objective Group:||Clinical Health (Organs, Diseases and Abnormal Conditions)|
|Objective Field:||Nervous System and Disorders|
|Author:||Landowski, LM (Dr Lila Landowski)|
|Author:||Gasperini, RJ (Dr Rob Gasperini)|
|Author:||Taylor, BVM (Professor Bruce Taylor)|
|Author:||West, AK (Professor Adrian West)|
|Author:||Foa, LC (Professor Lisa Foa)|
|Deposited By:||Wicking Dementia Research and Education Centre|
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