Collapsin Response Mediator Protein 2 and Endophilin2 Coordinate Regulation of AMPA Receptor GluA1 Subunit Recycling.

Jiong Li,Yichen Yin,Caihui Cha,Yong Wang,Guoqing Guo,Xueling Li,Jifeng Zhang,Yuxin Jiang

doi:10.3389/fnmol.2020.00128

Abstract

The dynamic trafficking of AMPA receptors (AMPARs), which enables the endocytosis, recycling, and exocytosis of AMPARs, is crucial for synaptic plasticity. Endophilin2, which directly interacts with the GluA1 subunit of AMPARs, plays an important role in AMPAR endocytosis. Collapsin response mediator protein 2 (CRMP2) promotes the maturation of the dendritic spine and can transfer AMPARs to the membrane. Although the mechanisms of AMPAR endocytosis and exocytosis are well known, the exact molecular mechanisms underlying AMPAR recycling remain unclear. Here, we report a unique interaction between CRMP2 and endophilin2. Our results showed that overexpression of CRMP2 and endophilin2 increased the amplitude and frequency of miniature excitatory synaptic currents (mEPSCs) and modestly enhanced AMPAR levels in hippocampal neurons. Furthermore, the CRMP2 and endophilin2 overexpression phenotype failed to occur when the interaction between these two proteins was inhibited. Further analysis revealed that this interaction was regulated by CRMP2 phosphorylation. The phosphorylation of CRMP2 inhibited its interaction with endophilin2; this was mainly affected by the phosphorylation of Thr514 and Ser518 by glycogen synthase kinase (GSK) 3β. CRMP2 phosphorylation increased degradation and inhibited the surface expression of AMPAR GluA1 subunits in cultured hippocampal neurons. However, the dephosphorylation of CRMP2 inhibited degradation and promoted the surface expression of AMPAR GluA1 subunits in cultured hippocampal neurons. Taken together, our data demonstrated that the interaction between CRMP2 and endophilin2 was conductive to the recycling of AMPA receptor GluA1 subunits in hippocampal neurons.

Highlights

AMPA-type glutamate receptors (AMPARs) are tetrameric assemblies of two dimers that consist of four subunits (GluA1–GluA4); the predominant conformation involves GluA1/GluA2 and GluA2/GluA3 heteromers (Lu et al, 2009; Herguedas et al, 2016)
These results suggested that Collapsin response mediator protein 2 (CRMP2) might be able to bind to endophilin2 through an electrostatic interaction
The results showed that GST-Endo2 interacted with CRMP2 (Figure 1C) and that GST-CRMP2 interacted with endophilin2 (Figure 1D)

Summary

Introduction

AMPA-type glutamate receptors (AMPARs) are tetrameric assemblies of two dimers that consist of four subunits (GluA1–GluA4); the predominant conformation involves GluA1/GluA2 and GluA2/GluA3 heteromers (Lu et al, 2009; Herguedas et al, 2016). The dynamic trafficking of AMPARs into and out of synaptic membranes involves the regulation of the number of AMPARs at the synaptic plasma membrane and is crucial for synaptic plasticity (Huganir and Nicoll, 2013). The number of synaptic AMPARs is regulated through endocytosis, exocytosis, and endosomal sorting, which results in the recycling of AMPARs back to the plasma membrane or degradation in the lysosome (van der Sluijs and Hoogenraad, 2011; Parkinson and Hanley, 2018). This dynamic behavior of AMPARs is usually regulated by protein–protein interactions (Bissen et al, 2019)

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