Multiple ubiquitin conjugates are present in rat brain synaptic membranes and postsynaptic densities

Chapman, Andrew. P.; Smith, Stuart; Rider, Christopher C.; Beesley, Philip

doi:10.1016/0304-3940(94)90459-6

Cited by 30 publications

(16 citation statements)

References 17 publications

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“…The observation that multiple membrane proteins of unknown identity are conjugated with ubiquitin in brain synaptic membranes and postsynaptic densities lends further support to the idea that ubiquitination of membrane proteins is a widespread phenomenon in the mammalian brain (65).…”

Section: Potential Roles Of Receptor Ubiquitination In Synaptic Develmentioning

confidence: 52%

Ubiquitination Precedes Internalization and Proteolytic Cleavage of Plasma Membrane-bound Glycine Receptors

Büttner¹,

Sadtler²,

Leyendecker³

et al. 2001

Journal of Biological Chemistry

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The inhibitory glycine receptor (GlyR) in developing spinal neurones is internalized efficiently upon antagonist inhibition. Here we used surface labeling combined with affinity purification to show that homopentameric ␣1 GlyRs generated in Xenopus oocytes are proteolytically nicked into fragments of 35 and 13 kDa upon prolonged incubation. Nicked GlyRs do not exist at the cell surface, indicating that proteolysis occurs exclusively in the endocytotic pathway. Consistent with this interpretation, elevation of the lysosomal pH, but not the proteasome inhibitor lactacystin, prevents GlyR cleavage. Prior to internalization, ␣1 GlyRs are conjugated extensively with ubiquitin in the plasma membrane. Our results are consistent with ubiquitination regulating the endocytosis and subsequent proteolysis of GlyRs residing in the plasma membrane. Ubiquitin-conjugating enzymes thus may have a crucial role in synaptic plasticity by determining postsynaptic receptor numbers.The efficiency of synaptic transmission depends critically on a dense packing of neurotransmitter receptors in the postsynaptic membrane. At fast synapses, ligand-gated ion channels (LGICs) 1 mediate the postsynaptic response. Different lines of evidence indicate that the distribution and density of LGICs in the plasma membrane are regulated tightly. In differentiating muscle fibers, the formation of a densely packed postsynaptic matrix of nicotinic acetylcholine receptors (nAChRs) at the developing motor endplate requires restriction of gene expression to subsynaptic nuclei, efficient internalization and degradation of extrasynaptic receptors, synaptic clustering by rapsyn, and slowing of the turnover of synaptically accumulated nAChRs (1, 2). Inversely, muscle denervation (2) or blockade of neurotransmission by ␣-bungarotoxin (3) causes a loss of nAChRs from the postsynaptic membrane because of an increased rate of protein turnover (4). Because nAChR degradation occurs only after internalization and lysosomal targeting of the receptor protein (4, 5

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Section: Potential Roles Of Receptor Ubiquitination In Synaptic Develmentioning

confidence: 52%

Ubiquitination Precedes Internalization and Proteolytic Cleavage of Plasma Membrane-bound Glycine Receptors

Büttner¹,

Sadtler²,

Leyendecker³

et al. 2001

Journal of Biological Chemistry

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“…Whether CDCrel-1 regulates dopamine release awaits further clarification, but failure of CDCrel-1 to be degraded by familial-linked Parkin mutations could increase the steady-state level of CDCrel-1 and thus potentially inhibit dopamine release and contribute to a Parkinsonian state. The mechanism underlying the degradation and turnover of synaptic vesicle-associated proteins has not been clarified, despite the identification of ubiquitin in the postsynaptic density and synaptic terminals (38)(39)(40). However, it is likely that Parkin or other nervous system-enriched E3s may play a prominent role in regulation of synaptic vesicle-associated protein levels.…”

Section: Discussionmentioning

confidence: 99%

Parkin functions as an E2-dependent ubiquitin– protein ligase and promotes the degradation of the synaptic vesicle-associated protein, CDCrel-1

Zhang

Gao

Chung

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

907

744

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P arkinson's disease (PD) is the second most prevalent neurodegenerative disorder, but the etiology remains poorly understood (1, 2). Patients with PD suffer from rigidity, slowness of movement, tremor, and disturbances of balance (1, 2). PD is characterized by the progressive loss of dopamine-containing neurons in the substantia nigra pars compacta (3, 4) and the accumulation of Lewy bodies, proteinaceous intracytoplasmic accumulations of eosinophilic material that stain for ubiquitin (5). Novel insights into the molecular mechanisms of the pathogenesis of PD have come from the identification of genes associated with rare forms of familial PD (6). Mutations in ␣-synuclein (A53T and A30P) are linked to autosomal dominant PD (7,8). This led to the discovery that ␣-synuclein is a major component of Lewy bodies and suggests that derangements in ␣-synuclein could be a major cause or contributor to the pathogenesis of sporadic PD (9, 10). Consistent with this notion are observations that overexpression of ␣-synuclein in transgenic fruit flies and mice causes a Parkinsonian phenotype and replicates many of the pathological features of PD (11-13).Other autosomal dominant genes or loci linked to PD have been described and include a mutation (I93M) in ubiquitin carboxyl-terminal-hydrolase-L1 (14), a member of the ubiquitin C-terminal hydrolase family that hydrolyzes small C-terminal adducts of ubiquitin to generate ubiquitin monomers and is involved in facilitating the degradation and processing of proteins through the 26 S proteasome. Thus, derangements in ubiquitin processing may be linked to the pathogenesis of PD. Linkages to chromosome 2P and 4P have been described, as well as yet to be identified loci, but the genes await identification (15-17).Mutations in the Parkin gene are responsible for autosomal recessive PD (18). Several Parkin-associated pedigrees have been described with both deletions and point mutations, as well as compound heterozygosity causing autosomal recessive PD (19)(20)(21). Recent studies suggest that mutations in Parkin are the major cause of autosomal recessive familial PD (19); thus, understanding the function of Parkin and how mutations interfere with the function of Parkin may provide novel insights into the pathogenesis of PD. The function of the Parkin protein remains unknown. However, Parkin shows mild homology to ubiquitin at the N terminus and contains two ring-finger motifs and an in-between ring-finger (IBR) domain at the C terminus (22). Recently, a few proteins with ring-finger motifs similar to Parkin were shown to be involved in E2-dependent ubiquitination (23-26). Ubiquitination requires the ATP-dependent activation of ubiquitin by the ubiquitin-activating enzyme E1. Ubiquitin is transferred to an E2 ubiquitin-conjugating enzyme, which works in conjunction with an E3 ubiquitin-protein ligase to ubiquitinate substrate proteins (23,24). The existence of two ring-finger motifs and the N-terminal homology to ubiquitin suggests that Parkin may be involved in the ubiquitination pathw...

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“…The Ubiquitination System-Previous studies indicated that many PSD proteins are ubiquitin-conjungated (82). As the ubiquitination/proteasome (Ub-Pr) pathway is a major route used to regulate many critical cellular proteins that must be rapidly destroyed (83), it was proposed that the Ub-Pr system regulates the synaptic protein composition and thereby also modulates functioning of the synapse (84).…”

Section: Discussionmentioning

confidence: 99%

Proteomics Analysis of Rat Brain Postsynaptic Density

Hornshaw

Schors

et al. 2004

Journal of Biological Chemistry

235

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The postsynaptic density contains multiple protein complexes that together relay the presynaptic neurotransmitter input to the activation of the postsynaptic neuron. In the present study we took two independent proteome approaches for the characterization of the protein complement of the postsynaptic density, namely 1) two-dimensional gel electrophoresis separation of proteins in conjunction with mass spectrometry to identify the tryptic peptides of the protein spots and 2) isolation of the trypsin-digested sample that was labeled with isotope-coded affinity tag, followed by liquid chromatography-tandem mass spectrometry for the partial separation and identification of the peptides, respectively. Functional grouping of the identified proteins indicates that the postsynaptic density is a structurally and functionally complex organelle that may be involved in a broad range of synaptic activities. These proteins include the receptors and ion channels for glutamate neurotransmission, proteins for maintenance and modulation of synaptic architecture, sorting and trafficking of membrane proteins, generation of anaerobic energy, scaffolding and signaling, local protein synthesis, and correct protein folding and breakdown of synaptic proteins. Together, these results imply that the postsynaptic density may have the ability to function (semi-) autonomously and may direct various cellular functions in order to integrate synaptic physiology.The majority of excitatory neurotransmission in the brain occurs via glutamatergic synapses. In the presynaptic element of the synapse, specialized secretion machinery determines the activity-dependent membrane fusion of glutamate-containing vesicles and the release of transmitter into the synaptic cleft. In the postsynaptic element, glutamate receptors and downstream signal transduction are organized by the protein assembly of the postsynaptic density (PSD). 1 Both the presynaptic release machinery and the PSD are electron-dense assemblies (1, 2), in which proteins are thought to be organized into distinct functional complexes (3-5) that may be dynamically regulated by neuronal activity (6 -8). The modulation of this molecular architecture of the synapse is at the basis of synaptic plasticity (6 -8), and aberrations thereof may underlie neuronal disorders.In view of the importance of the PSD in glutamatergic neurotransmission and its involvement in neuroplasticity, considerable efforts have been made to identify its protein constituents as a prelude to understand the molecular basis of PSD functioning. In the past several years, yeast two-hybrid technology has been extensively used to characterize proteins that interact with the glutamate receptors and may constitute core elements of the PSD involved in the regulation of receptor trafficking and signaling (reviewed in Refs. 9 -11). Based largely on these studies a protein-protein interaction map of the PSD has emerged. In brief, the model posits that the postsynaptic receptor complexes are localized by scaffolding proteins such as the s...

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Multiple ubiquitin conjugates are present in rat brain synaptic membranes and postsynaptic densities

Cited by 30 publications

References 17 publications

Ubiquitination Precedes Internalization and Proteolytic Cleavage of Plasma Membrane-bound Glycine Receptors

Ubiquitination Precedes Internalization and Proteolytic Cleavage of Plasma Membrane-bound Glycine Receptors

Parkin functions as an E2-dependent ubiquitin– protein ligase and promotes the degradation of the synaptic vesicle-associated protein, CDCrel-1

Proteomics Analysis of Rat Brain Postsynaptic Density

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