PMC

Interactions between GluA2 and GRIP, but not PICK1, are required for mAChR-LTD. (A) Neither pep2-SVKE (n = 6) nor pep2-EVKI (n = 9) has any effect on mAChR-LTD. (B) Pep2-SVKI prevents mAChR-LTD (n = 8). (C) Pep2-SVKE (n = 6) has no effect on mGluR-LTD. (D) Pep2-SVKI (n = 6) has no effect on mGluR-LTD.

Interaction between liprin α and GRIP is required for mAChR-LTD. (A) Intracellular infusion of the C terminal fragment of liprin α (TVRTYSC) prevents induction of mAChR-LTD (n = 6). (B) A control peptide (TVRTASC) has no affect on mAChR-LTD (n = 5). (C) TVRTYSC (n = 7) has no effect on mGluR-LTD. (D) TVRTASC (n = 8) has no effect on mGluR-LTD. (E) TVRTYSC (n = 6) has no effect on NMDAR-LTD. (F) TVRTASC (n = 6) has no effect on NMDAR-LTD.

A novel mechanism of LTD involving liprin-α and LAR. Activation of mAChRs leads to a G-protein dependent mAChR-LTD that does not involve the canonical pathway (IP3 and PKC). The data can most simply be explained by GRIP acting as a targeting molecule that brings LAR and the GluA2 subunit of AMPARs into contact. This then enables LAR to dephosphorlyate a tyrosine residue (such as YGIESVKI on GluA2) which initiates the removal of the AMPAR from the synapse.

Signalling mechanisms involved in mAChR-LTD. (A) Cyclopiazonic acid (2 μM) has no effect on mAChR-LTD (n = 6). (B) Ro 32-0432 (10 μM) has no effect on mAChR-LTD (n = 6). (C) Okadaic acid (100 nM) has no effect on mAChR-LTD (n = 5). (D) Anisomycin (20 μM) has no effect on mAChR-LTD (n = 7). (E) Orthovanadate (100 μM) prevents the induction of mAChR-LTD (n = 5). (F) GDPβS (1 mM) blocks the induction of mAChR-LTD (n = 6). (G) A summary of results from control (n = 8), BAPTA (n = 9), cyclopiazonic acid (n = 6), PKC19–31 (n = 9), Ro 32-0432 (n = 6), okadaic acid (n = 5), cyclosporin A (n = 7), anisomycin (n = 7), cycloheximide (n = 7), orthovanadate (n = 5), phenylarsine oxide (n = 7) and GDPβS (n = 6), experiments. * P < 0.05 vs control ** P < 0.01 vs control.

Properties of CCh-induced LTD in the CA1 region of the hippocampus. (A) A pooled data (n = 8) of EPSC amplitude vs time to show that carbachol application (CCh, 50 μM, 10 min) induces mAChR-LTD. (B) D-AP5 (50 μM) has no effect on mAChR-LTD (n = 9). (C) mAChR-LTD was prevented by bath application of an M1 mAChR antagonist, pirenzepine (0.5 μM, n = 5). (D) The M1 specific agonist, 77-LH-28-1, induces LTD (n = 6). (E) D-AP5 (50 μM) has no effect on LTD induced by 77-LH-28-1 (n = 5). (F) Pirenzepine (0.5 μM) prevents LTD induced by 77-LH-28-1 (n = 7). (G) Co-application of LY367385 (100 μM) and MPEP (50 μM) has no effect on mAChR-LTD (n = 6). (H) An example of biotinylation from hippocampal slices. Pooled data (n = 4) shows that CCh induces internalisation of GluA2. Error bars represent s.e.m.