Nedd4‐mediated AMPA receptor ubiquitination regulates receptor turnover and trafficking

Abstract

J. Neurochem. (2011) 119, 27–39. Abstract α‐Amino‐3‐hydroxy‐5‐methyl‐isoxazole‐4‐propionic acid receptors (AMPARs) are the primary mediators of excitatory synaptic transmission in the brain. Alterations in AMPAR localization and turnover have been considered critical mechanisms underpinning synaptic plasticity and higher brain functions, but the molecular processes that control AMPAR trafficking and stability are still not fully understood. Here, we report that mammalian AMPARs are subject to ubiquitination in neurons and in transfected heterologous cells. Ubiquitination facilitates AMPAR endocytosis, leading to a reduction in AMPAR cell‐surface localization and total receptor abundance. Mutation of lysine residues to arginine residues at the glutamate receptor subunit 1 (GluA1) C‐terminus dramatically reduces GluA1 ubiquitination and abolishes ubiquitin‐dependent GluA1 internalization and degradation, indicating that the lysine residues, particularly K868, are sites of ubiquitination. We also find that the E3 ligase neural precursor cell expressed, developmentally down‐regulated 4 (Nedd4) is enriched in synaptosomes and co‐localizes and associates with AMPARs in neurons. Nedd4 expression leads to AMPAR ubiquitination, leading to reduced AMPAR surface expression and suppressed excitatory synaptic transmission. Conversely, knockdown of Nedd4 by specific siRNAs abolishes AMPAR ubiquitination. These data indicate that Nedd4 is the E3 ubiquitin ligase responsible for AMPAR ubiquitination, a modification that regulates multiple aspects of AMPAR molecular biology including trafficking, localization and stability.

Lys-63-linked Ubiquitination by E3 Ubiquitin Ligase Nedd4-1 Facilitates Endosomal Sequestration of Internalized α-Synuclein

“…Because Nedd4 localizes to the cytosolic space by associating with the inner plasma membrane leaflet via its C2 domain, Nedd4-1 likely preferentially catalyzes juxtamembrane aS localization. This notion is supported by previous studies showing that Nedd4-1-mediated ubiquitination is closely linked to the turnover and trafficking of cell-surface receptors (31,32). Although aS does not contain the canonical PPXY motif known to interact with the WW domain of Nedd4-1, the WW domain can recognize several motifs other than PPXY with varying affinities (33).…”

In vivo quantitative proteomics of somatosensory cortical synapses shows which protein levels are modulated by sensory deprivation

“…Ubr4 has been shown previously to stabilize neuronal processes by stabilizing microtubules, and knockdown of this protein leads to thin, crooked neurites (71). Nedd4 has been implicated previously in the ubiquitination of GluA1, leading to its internalization and thereby reducing synaptic strength (72,88). Therefore, the up-regulation of Nedd4 in these deprived synapses may be implicated in the observed reduction in synaptic GluA1 (Table 1), leading to weaker synapses.…”

Stargazin regulates AMPA receptor trafficking through adaptor protein complexes during long-term depression

“…For example, in mice that lack the genes encoding GluA2 and GluA3 throughout development, the hippocampal LTD is normal, except that it is largely resistant to the dynamin inhibitory peptide 39 , indicating that LTD is no longer mediated by clathrin-dependent endocytosis in these mice. Furthermore, the application of AMPA, but not NMDA, can induce the ubiquitination of AMPA receptors [40][41][42] , which can be recruited to clathrin-coated pits for endocytosis via the APs epsin and eps15 (ref. 43).…”