By Simon Hackett
Retinal ganglion cells (RGCs) are neurons located near the ganglionic cell layer of the retina. These cells receive impulses from photoreceptor cells via bipolar and amacrine cells mediated by AMPA-class glutamate receptors (AMPA receptors). Two types of these receptors exist: receptors lacking GluA2 subunits, permeable to calcium ions, and those with a GluA2 subunit (or subunits), impermeable to calcium ions. The presence of the GluA2 subunit, and resulting permeability to calcium ions, influences the inward and outward currents of a cell. Without the GluA2 subunit, neuronal cells become inwardly rectifying and produce less outward current.
Periods of low synaptic activity, such as those induced by prolonged periods spent in darkness, increase the proportion of GluA2-negative AMPA receptors at the synaptic membrane of RGCs. This is brought about by a shift in the cycling of surface GluA2‑positive receptors, with a bias towards internal pooling. In addition to this regulation by trafficking, a number of other regulatory processes exist at the level of gene expression, RNA editing and receptor assembly. A recent paper by Casimiro et al. takes a closer look at the proteins involved in AMPA receptor trafficking, and whether they provide a link between synaptic activity and AMPA receptor cycling in RGCs.
The authors were able to demonstrate, using Proteintech’s GluA2 antibody, that darkness causes a significant decrease in surface GluA2 and also alters the expression of GRIP, PICK1 and Arc – three proteins linked to GluA2 trafficking. The findings presented by Casimiro and colleagues suggest that changes in the expression of AMPA receptor regulatory proteins can temper the trafficking of these receptors following changes in neuronal activity. Moreover this indicates that the cycling, or trafficking, of AMPA receptors can modulate synaptic function and play an integral role in their plasticity.
Simon Hackett completed his undergraduate degree in Biochemistry followed by a master’s degree in Pharmacology. Following this, Simon undertook a D.Phil in Immunology and Regenerative Medicine. He is now undertaking a post-graduate medical degree with the intention of becoming an academic clinical scientist.
|Gene Symbol||Protein Name||Cat. No.||Type||Application|
|ARC||ARG3.1||16290-1-AP||Rabbit poly||ELISA, WB, IHC|
|GRIA||GluA2||11994-1-AP||Rabbit poly||ELISA, WB, IHC|
|GRIP1||Glutamate receptor interacting protein 1||22398-1-AP||Rabbit poly||ELISA, WB|
|PICK1||PRKCA-binding protein||10983-1-AP||Rabbit poly||ELISA, WB, IHC|