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Ubiquitination directly enhances activity of the deubiquitinating enzyme ataxin-3.

ABSTRACT: Deubiquitinating enzymes (DUBs) control the ubiquitination status of proteins in various cellular pathways. Regulation of the activity of DUBs, which is critically important to cellular homoeostasis, can be achieved at the level of gene expression, protein complex formation, or degradation. Here, we report that ubiquitination also directly regulates the activity of a DUB, ataxin-3, a polyglutamine disease protein implicated in protein quality control pathways. Ubiquitination enhances ubiquitin (Ub) chain cleavage by ataxin-3, but does not alter its preference for K63-linked Ub chains. In cells, ubiquitination of endogenous ataxin-3 increases when the proteasome is inhibited, when excess Ub is present, or when the unfolded protein response is induced, suggesting that the cellular functions of ataxin-3 in protein quality control are modulated through ubiquitination. Ataxin-3 is the first reported DUB in which ubiquitination directly regulates catalytic activity. We propose a new function for protein ubiquitination in regulating the activity of certain DUBs and perhaps other enzymes.

SUBMITTER: Todi SV

PROVIDER: S-EPMC2646149 | biostudies-literature | 2009 Feb

REPOSITORIES: biostudies-literature

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Ubiquitination directly enhances activity of the deubiquitinating enzyme ataxin-3.

Todi Sokol V SV Winborn Brett J BJ Scaglione K Matthew KM Blount Jessica R JR Travis Sue M SM Paulson Henry L HL

The EMBO journal 20090115 4

Deubiquitinating enzymes (DUBs) control the ubiquitination status of proteins in various cellular pathways. Regulation of the activity of DUBs, which is critically important to cellular homoeostasis, can be achieved at the level of gene expression, protein complex formation, or degradation. Here, we report that ubiquitination also directly regulates the activity of a DUB, ataxin-3, a polyglutamine disease protein implicated in protein quality control pathways. Ubiquitination enhances ubiquitin ( ...[more]

PMID: 19153604

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Project description:Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPARs) are the primary mediators for inter-neuronal communication and play a crucial role in higher brain functions including learning and memory. Our previous work demonstrated that AMPARs are subject to ubiquitination by the E3 ligase Nedd4, resulting in EPS15-mediated receptor internalization and Ubiquitin (Ub)-proteasome pathway (UPP)-dependent degradation. Protein ubiquitination is a highly dynamic and reversible process, achieved via the balance between ubiquitination and deubiquitination. However, deubiquitination of mammalian AMPARs and the responsible deubiquitinating enzymes remain elusive. In this study, we identify USP46 as the deubiquitinating enzyme for AMPARs. We find that AMPARs are subject to K63 type ubiquitination, and USP46 is able to deubiquitinate AMPARs in vivo and in vitro. In heterologous cells and neurons, expression of USP46 results in a significant reduction in AMPAR ubiquitination, accompanied by a reduced rate in AMPAR degradation and an increase in surface AMPAR accumulation. By contrast, knockdown of USP46 by RNAi leads to elevated AMPAR ubiquitination and a reduction in surface AMPARs at synapses in neurons. Consistently, miniature excitatory postsynaptic currents recordings show reduced synaptic strength in neurons expressing USP46-selective RNAi. These results demonstrate USP46-mediated regulation of AMPAR ubiquitination and turnover, which may play an important role in synaptic plasticity and brain function. Protein ubiquitination is a highly dynamic and reversible process, achieved via the balance between ubiquitination and deubiquitination. The glutamatergic AMPARs, which mediate most of the excitatory synaptic transmission in the brain, are known to be subjected to Nedd4-mediated ubiquitination; however, the deubiquitination process and the responsible deubiquitinating enzymes (DUBs) for mammalian AMPARs remain elusive. We find that AMPARs are subject to K63-type ubiquitination, and identify USP46 as the DUB for AMPARs. USP46 deubiquitinates AMPARs in vitro and in vivo. Up- or down-regulation of USP46 leads to changes in AMPAR ubiquitination, surface expression, and trafficking, as well as the strength of synaptic transmission. USP46-mediated regulation of AMPAR ubiquitination and turnover may play an important role in synaptic plasticity and brain function.

Dataset Information

Ubiquitination directly enhances activity of the deubiquitinating enzyme ataxin-3.

Publications

Ubiquitination directly enhances activity of the deubiquitinating enzyme ataxin-3.

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