Research

A novel mechanism of hippocampal LTD involving muscarinic receptor-triggered interactions between AMPARs, GRIP and liprin-α

Bryony A Dickinson¹ , Jihoon Jo^1,2 , Heon Seok¹ , Gi Hoon Son¹ , Daniel J Whitcomb^1,2 , Ceri H Davies³ , Morgan Sheng⁴ , Graham L Collingridge² and Kwangwook Cho^1,2

¹  Henry Wellcome Laboratories for Integrative Neuroscience and Endocrinology (LINE), Faculty of Medicine and Dentistry, University of Bristol, Whitson Street, Bristol BS1 3NY, UK

²  Department of Anatomy, University of Bristol, MRC Centre for Synaptic Plasticity, University Walk, Bristol BS8 1TD, UK

³  Neurosciences CEDD, GlaxoSmithKline, New Frontiers Science Park North, Third Avenue, Harlow, Essex CM19 5AW, UK

⁴  Department of Brain and Cognitive Sciences, Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA

author email corresponding author email

Molecular Brain 2009, 2:18doi:10.1186/1756-6606-2-18

Published:	17 June 2009

Abstract

Background

Long-term depression (LTD) in the hippocampus can be induced by activation of different types of G-protein coupled receptors, in particular metabotropic glutamate receptors (mGluRs) and muscarinic acethycholine receptors (mAChRs). Since mGluRs and mAChRs activate the same G-proteins and isoforms of phospholipase C (PLC), it would be expected that these two forms of LTD utilise the same molecular mechanisms. However, we find a distinct mechanism of LTD involving GRIP and liprin-α.

Results

Whilst both forms of LTD require activation of tyrosine phosphatases and involve internalisation of AMPARs, they use different molecular interactions. Specifically, mAChR-LTD, but not mGluR-LTD, is blocked by peptides that inhibit the binding of GRIP to the AMPA receptor subunit GluA2 and the binding of GRIP to liprin-α. Thus, different receptors that utilise the same G-proteins can regulate AMPAR trafficking and synaptic efficacy via distinct molecular mechanisms.

Conclusion

Our results suggest that mAChR-LTD selectively involves interactions between GRIP and liprin-α. These data indicate a novel mechanism of synaptic plasticity in which activation of M1 receptors results in AMPAR endocytosis, via a mechanism involving interactions between GluA2, GRIP and liprin-α.