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Integrin alpha4beta1 (VLA-4) expression and activity in retinal and peripheral neurons
Sherry T Hikita1, Gordon M Cann, Kevin L Wingerd
1Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, CA 93106, USA.
Molecular and Cellular Neurosciences
|July 3, 2003
Summary
Integrin alpha4beta1 promotes neurite outgrowth in retinal neurons by binding to VCAM-1 and osteopontin. This suggests a role for alpha4beta1 in neuronal development and optic nerve formation.
Area of Science:
- Neuroscience
- Cell Biology
- Developmental Biology
Background:
- Integrin alpha4beta1 is crucial for inflammation and hematopoiesis.
- Its specific functions in neuronal development remain largely unknown.
- The alpha4 subunit is expressed in mouse retinal ganglion cells (RGCs) and neuroblasts during development.
Purpose of the Study:
- To investigate the role of integrin alpha4beta1 in neuronal development.
- To determine if alpha4beta1 mediates neurite outgrowth in retinal neurons.
- To identify potential in vivo ligands for alpha4beta1 in the optic nerve.
Main Methods:
- Culturing mouse retinal neurons on known alpha4 integrin ligands: soluble vascular cell adhesion molecule 1 (rsVCAM-1), fibronectin, and osteopontin (OPN).
- Using function-blocking antibodies against alpha4 and beta1 integrin subunits to assess their role in neurite outgrowth.
- Immunohistochemical detection of OPN in the RGC fiber layer and optic nerve.
Main Results:
- rsVCAM-1, fibronectin, and OPN significantly induced neurite outgrowth in cultured retinal neurons.
- Function-blocking antibodies against alpha4 integrin diminished this outgrowth.
- Antibodies against the beta1 subunit blocked outgrowth on OPN, confirming the involvement of the alpha4beta1 heterodimer.
- OPN was detected in the RGC fiber layer and optic nerve.
Conclusions:
- Integrin alpha4beta1 is an active receptor mediating neurite outgrowth on specific ligands in retinal neurons.
- Osteopontin may serve as an in vivo ligand for alpha4beta1 in the developing optic nerve.
- Integrin alpha4beta1 likely plays a significant role in the development of various neuronal cell types, including RGCs.