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Updated: Aug 29, 2026
Müller Glia Cell Activation in a Laser-induced Retinal Degeneration and Regeneration Model in Zebrafish
Published on: October 27, 2017
A novel cAMP-dependent pathway activates neuronal integrin function in retinal neurons
Jonathan K Ivins1, Melissa K Parry, Dorothy A Long
1Department of Neurosurgery, University of Texas Health Science Center at Houston, Houston, Texas 77030, USA. jonathan.k.ivins@uth.tmc.edu
Abstract:
Retinal neurons lose the ability to attach to and extend neurites on substrata of laminin-1 (LN-1) during late embryogenesis, in a time frame that corresponds to target innervation. Although this developmental loss correlates with a modest downregulation of integrin expression, we have shown previously that these neurons use the same laminin-binding integrins for outgrowth on other laminin isoforms to which responsivity has not been lost (Ivins et al., 1998), suggesting that integrin functional states may be a critical point of regulation. Consistent with this view, expression of an activated mutant of R-ras, an activator of integrin function, restores integrin-dependent outgrowth of late embryonic retinal neurons on LN-1 (Ivins et al., 2000). Because cyclic nucleotides have been implicated in the regulation of integrin function in non-neuronal cells, as well as in the regulation of growth cone responses to various axon growth inhibitors, we asked whether raising cAMP levels in late embryonic retinal neurons could activate neuronal integrin function and restore neurite outgrowth on LN-1. We find that, similar to R-ras expression, raising cAMP levels in these neurons promotes alpha6beta1 integrin-dependent neurite outgrowth. Surprisingly, these effects of cAMP are independent of protein kinase A and the EPAC (exchange protein directly activated by cAMP)/Rap pathway and suggest the existence of a novel cAMP-dependent mechanism.
Insights
Elevated cAMP levels restore neurite outgrowth in retinal neurons by activating integrin function on laminin-1 substrates. This novel mechanism bypasses traditional pathways, offering new insights into neuronal development and axon guidance.
Area of Science:
- Neuroscience
- Developmental Biology
- Cell Biology
Background:
- Retinal neurons lose the ability to extend neurites on laminin-1 (LN-1) during late embryogenesis.
- This loss correlates with integrin expression changes but suggests functional regulation, as integrins remain responsive to other laminin isoforms.
Purpose of the Study:
- To investigate whether increasing cyclic adenosine monophosphate (cAMP) levels can activate integrin function and restore neurite outgrowth on LN-1 in late embryonic retinal neurons.
- To explore the regulatory mechanisms of cAMP in neuronal integrin function and axon growth.
Main Methods:
- Utilized late embryonic retinal neurons.
- Manipulated intracellular cAMP levels.
- Assessed alpha6beta1 integrin-dependent neurite outgrowth on laminin-1 (LN-1) substrata.
- Investigated the involvement of protein kinase A and the EPAC/Rap pathway.
Main Results:
- Raising cAMP levels in retinal neurons promoted alpha6beta1 integrin-dependent neurite outgrowth on LN-1.
- This effect was similar to the restoration achieved by expressing an activated R-ras mutant.
- The cAMP-mediated effects were independent of protein kinase A and the EPAC/Rap pathway.
Conclusions:
- Elevated cAMP levels can restore the ability of late embryonic retinal neurons to extend neurites on laminin-1.
- A novel cAMP-dependent mechanism, independent of PKA and EPAC/Rap, regulates neuronal integrin function and neurite outgrowth.
- Findings suggest new therapeutic targets for promoting neuronal regeneration.
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