Guidance of Axons by Local Coupling of Retrograde Flow to Point Contact Adhesions
| Autor: | Timothy M. Gomez, Kate M. Hagen, Erik W. Dent, Robert H. Nichol, Derek C. Lumbard |
|---|---|
| Rok vydání: | 2016 |
| Předmět: |
0301 basic medicine
Role of cell adhesions in neural development Growth Cones Leading edge membrane Biology Axonal Transport Filamentous actin Xenopus laevis 03 medical and health sciences Cell Adhesion Animals Polylysine Growth cone Paxillin Neurons General Neuroscience Articles Anatomy Actin cytoskeleton Actins Axons Rats 030104 developmental biology Spinal Cord biology.protein Axoplasmic transport Biophysics Axon guidance Laminin |
| Zdroj: | The Journal of Neuroscience. 36:2267-2282 |
| ISSN: | 1529-2401 0270-6474 |
| Popis: | Growth cones interact with the extracellular matrix (ECM) through integrin receptors at adhesion sites termed point contacts. Point contact adhesions link ECM proteins to the actin cytoskeleton through numerous adaptor and signaling proteins. One presumed function of growth cone point contacts is to restrain or “clutch” myosin-II-based filamentous actin (F-actin) retrograde flow (RF) to promote leading edge membrane protrusion. In motile non-neuronal cells, myosin-II binds and exerts force upon actin filaments at the leading edge, where clutching forces occur. However, in growth cones, it is unclear whether similar F-actin-clutching forces affect axon outgrowth and guidance. Here, we show inXenopusspinal neurons that RF is reduced in rapidly migrating growth cones on laminin (LN) compared with non-integrin-binding poly-d-lysine (PDL). Moreover, acute stimulation with LN accelerates axon outgrowth over a time course that correlates with point contact formation and reduced RF. These results suggest that RF is restricted by the assembly of point contacts, which we show occurs locally by two-channel imaging of RF and paxillin. Further, using micropatterns of PDL and LN, we demonstrate that individual growth cones have differential RF rates while interacting with two distinct substrata. Opposing effects on RF rates were also observed in growth cones treated with chemoattractive and chemorepulsive axon guidance cues that influence point contact adhesions. Finally, we show that RF is significantly attenuatedin vivo, suggesting that it is restrained by molecular clutching forces within the spinal cord. Together, our results suggest that local clutching of RF can control axon guidance on ECM proteins downstream of axon guidance cues.SIGNIFICANCE STATEMENTHere, we correlate point contact adhesions directly with clutching of filamentous actin retrograde flow (RF), which our findings strongly suggest guides developing axons. Acute assembly of new point contact adhesions is temporally and spatially linked to attenuation of RF at sites of forward membrane protrusion. Importantly, clutching of RF is modulated by extracellular matrix (ECM) proteins and soluble axon guidance cues, suggesting that it may regulate axon guidancein vivo. Consistent with this notion, we found that RF rates of spinal neuron growth cones were slowerin vivothan what was observedin vitro. Together, our study provides the best evidence that growth cone–ECM adhesions clutch RF locally to guide axonsin vivo. |
| Databáze: | OpenAIRE |
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