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E E Wanker

Publications and source records attributed to E E Wanker.

At least 19 recordsLinked to original sources
PubMed2006

Huntingtin interacts with the receptor sorting family protein GASP2.

Protein interaction networks are useful resources for the functional annotation of proteins. Recently, we have generated a highly connected protein-protein interaction network for Huntington's disease (HD) by automated yeast two-hybrid (Y2H) screening (Goehler et al., 2004). The network included several novel direct interaction partners for the disease protein huntingtin (htt). Some of these interactions, however, have not been validated by independent methods. Here we describe the verification of the interaction between htt and GASP2 (G protein-coupled receptor associated sorting protein 2), a protein involved in membrane receptor degradation. Using membrane-based and classical coimmunoprecipitation assays we demonstrate that htt and GASP2 form a complex in cotransfected mammalian cells. Moreover, we show that the two proteins colocalize in SH-SY5Y cells, raising the possibility that htt and GASP2 interact in neurons. As the GASP protein family plays a role in G protein-coupled receptor sorting, our data suggest that htt might influence receptor trafficking via the interaction with GASP2.

Animals↗
PubMed2005

Parkin interacts with the proteasome subunit alpha4.

Mutations in the parkin gene encoding an E3 ligase are responsible for autosomal recessive Parkinson's disease. Putative parkin substrates and interacting partners have been identified, but the molecular mechanism underlying parkin-related neurodegeneration is still unclear. We have identified the 20S proteasomal subunit alpha4 (synonyms: PSMA7, XAPC7, subunit alpha type 7) as a new interacting partner of parkin. The C-terminal IBR-RING domain of parkin and the C-terminal part of alpha4 were essential for the interaction. Biochemical studies revealed that alpha4 was not a substrate for parkin-dependent ubiquitylation. Putative functions of the interaction might therefore be substrate presentation to the proteasome or regulation of proteasomal activity. Full-length parkin and parkin lacking the N-terminal ubiquitin-like domain slightly increased the proteasomal activity in HEK 293T cells, in line with the latter hypothesis.

Animals↗
PubMed2002

Aggregation of proteins with expanded glutamine and alanine repeats of the glutamine-rich and asparagine-rich domains of Sup35 and of the amyloid beta-peptide of amyloid plaques.

The exon-1 peptide of huntingtin has 51 Gln repeats and produces the symptoms of Huntington's disease in transgenic mice. Aggregation of the yeast Sup35 protein into prions has been attributed to its glutamine-rich and asparagine-rich domain. Here, we show that poly-L-asparagine forms polar zippers similar to those of poly-L-glutamine. In solution at acid pH, the glutamine-rich and asparagine-rich 18-residue Sup35 peptide, rendered soluble by the addition of two aspartates at the amino end and two lysines at the carboxyl end, gives a beta-sheet CD spectrum; it aggregates at neutral pH. A poly-alanine peptide D(2)A(10)K(2) gives an alpha-helical CD spectrum at all pHs and does not aggregate; a peptide with the sequence of the C-terminal helix of the alpha-chain of human hemoglobin, preceded by two aspartates and followed by two lysines, exhibits a random coil spectrum and does not aggregate either. Alignment of several beta-strands with the sequence of the 42-residue Alzheimer's amyloid beta-peptide shows that they can be linked together by a network of salt bridges. We also asked why single amino acid replacements can so destabilize the native structures of proteins that they unfold and form amyloids. The difference in free energy of a protein molecule between its native, fully ordered structure and an amorphous mixture of randomly coiled chains is only of the order of 10 kcal/mol. Theory shows that destabilization of the native structure by no more than 2 kcal/mol can increase the probability of nucleation of disordered aggregates from which amyloids could grow 130,000-fold.

Alanine↗
PubMed2001

Centrosome disorganization in fibroblast cultures derived from R6/2 Huntington's disease (HD) transgenic mice and HD patients.

Huntington's disease (HD) is a progressive neurological disorder caused by a CAG/polyglutamine repeat expansion. We have previously generated the R6/2 mouse model that expresses exon 1 of the human HD gene containing CAG repeats in excess of 150. These mice develop a progressive neurological phenotype with a rapid onset and progression. We show here that it is impossible to establish fibroblast lines from these mice at 12 weeks of age, whilst this can be achieved without difficulty at 6 and 9 weeks. Cultures derived from mice at 12 weeks contained a high frequency of dysmorphic cells, including cells with an aberrant nuclear morphology and a high frequency of micronuclei and large vacuoles. All of these features were also present in a line derived from a juvenile HD patient. Fibroblast lines derived from R6/2 mice and from HD patients were found to have a high frequency of multiple centrosomes which could account for all of the observed phenotypes including a reduced mitotic index, high frequency of aneuploidy and persistence of the midbody. We were unable to detect large insoluble polyglutamine aggregates in either the mouse or human lines. We have identified a novel progressive HD pathology that occurs in cells of non-central nervous system origin. An investigation of the pathological consequences of the HD mutation in these cells will provide insight into cellular basis of the disease.

Aneuploidy↗
PubMed2001

The huntingtin interacting protein HIP1 is a clathrin and alpha-adaptin-binding protein involved in receptor-mediated endocytosis.

The huntingtin interacting protein (HIP1) is enriched in membrane-containing cell fractions and has been implicated in vesicle trafficking. It is a multidomain protein containing an N-terminal ENTH domain, a central coiled-coil forming region and a C-terminal actin-binding domain. In the present study we have identified three HIP1 associated proteins, clathrin heavy chain and alpha-adaptin A and C. In vitro binding studies revealed that the central coiled-coil domain is required for the interaction of HIP1 with clathrin, whereas DPF-like motifs located upstream to this domain are important for the binding of HIP1 to the C-terminal 'appendage' domain of alpha-adaptin A and C. Expression of full length HIP1 in mammalian cells resulted in a punctate cytoplasmic immunostaining characteristic of clathrin-coated vesicles. In contrast, when a truncated HIP1 protein containing both the DPF-like motifs and the coiled-coil domain was overexpressed, large perinuclear vesicle-like structures containing HIP1, huntingtin, clathrin and endocytosed transferrin were observed, indicating that HIP1 is an endocytic protein, the structural integrity of which is crucial for maintenance of normal vesicle size in vivo.

Adaptor Protein Complex alpha Subunits↗
PubMed2001

Geldanamycin activates a heat shock response and inhibits huntingtin aggregation in a cell culture model of Huntington's disease.

Huntington's disease (HD) is a progressive neurodegenerative disorder with no effective treatment. Geldanamycin is a benzoquinone ansamycin that binds to the heat shock protein Hsp90 and activates a heat shock response in mammalian cells. In this study, we show by using a filter retardation assay and immunofluorescence microscopy that treatment of mammalian cells with geldanamycin at nanomolar concentrations induces the expression of Hsp40, Hsp70 and Hsp90 and inhibits HD exon 1 protein aggregation in a dose-dependent manner. Similar results were obtained by overexpression of Hsp70 and Hsp40 in a separate cell culture model of HD. This is the first demonstration that huntingtin protein aggregation in cells can be suppressed by chemical compounds activating a specific heat shock response. These findings may provide the basis for the development of a novel pharmacotherapy for HD and related glutamine repeat disorders.

Amino Acid Sequence↗
PubMed2001

Accumulation of mutant huntingtin fragments in aggresome-like inclusion bodies as a result of insufficient protein degradation.

The huntingtin exon 1 proteins with a polyglutamine repeat in the pathological range (51 or 83 glutamines), but not with a polyglutamine tract in the normal range (20 glutamines), form aggresome-like perinuclear inclusions in human 293 Tet-Off cells. These structures contain aggregated, ubiquitinated huntingtin exon 1 protein with a characteristic fibrillar morphology. Inclusion bodies with truncated huntingtin protein are formed at centrosomes and are surrounded by vimentin filaments. Inhibition of proteasome activity resulted in a twofold increase in the amount of ubiquitinated, SDS-resistant aggregates, indicating that inclusion bodies accumulate when the capacity of the ubiquitin-proteasome system to degrade aggregation-prone huntingtin protein is exhausted. Immunofluorescence and electron microscopy with immunogold labeling revealed that the 20S, 19S, and 11S subunits of the 26S proteasome, the molecular chaperones BiP/GRP78, Hsp70, and Hsp40, as well as the RNA-binding protein TIA-1, the potential chaperone 14-3-3, and alpha-synuclein colocalize with the perinuclear inclusions. In 293 Tet-Off cells, inclusion body formation also resulted in cell toxicity and dramatic ultrastructural changes such as indentations and disruption of the nuclear envelope. Concentration of mitochondria around the inclusions and cytoplasmic vacuolation were also observed. Together these findings support the hypothesis that the ATP-dependent ubiquitin-proteasome system is a potential target for therapeutic interventions in glutamine repeat disorders.

14-3-3 Proteins↗
PubMed2000

Hsp70 and hsp40 chaperones can inhibit self-assembly of polyglutamine proteins into amyloid-like fibrils.

The deposition of protein aggregates in neurons is a hallmark of neurodegenerative diseases caused by polyglutamine (polyQ) proteins. We analyzed the effects of the heat shock protein (Hsp) 70 chaperone system on the aggregation of fragments of huntingtin (htt) with expanded polyQ tracts. In vitro, Hsp70 and its cochaperone Hsp40 suppressed the assembly of htt into detergent-insoluble amyloid-like fibrils in an ATP-dependent manner and caused the formation of amorphous, detergent-soluble aggregates. The chaperones were most active in preventing fibrillization when added during the lag phase of the polymerization reaction. Similarly, coexpression of Hsp70 or Hsp40 with htt in yeast inhibited the formation of large, detergent-insoluble polyQ aggregates, resulting in the accumulation of detergent-soluble inclusions. Thus, the recently established potency of Hsp70 and Hsp40 to repress polyQ-induced neurodegeneration may be based on the ability of these chaperones to shield toxic forms of polyQ proteins and to direct them into nontoxic aggregates.

Amino Acid Sequence↗
PubMed2000

The Huntington's disease protein interacts with p53 and CREB-binding protein and represses transcription.

Huntington's Disease (HD) is caused by an expansion of a polyglutamine tract within the huntingtin (htt) protein. Pathogenesis in HD appears to include the cytoplasmic cleavage of htt and release of an amino-terminal fragment capable of nuclear localization. We have investigated potential consequences to nuclear function of a pathogenic amino-terminal region of htt (httex1p) including aggregation, protein-protein interactions, and transcription. httex1p was found to coaggregate with p53 in inclusions generated in cell culture and to interact with p53 in vitro and in cell culture. Expanded httex1p represses transcription of the p53-regulated promoters, p21(WAF1/CIP1) and MDR-1. httex1p was also found to interact in vitro with CREB-binding protein (CBP) and mSin3a, and CBP to localize to neuronal intranuclear inclusions in a transgenic mouse model of HD. These results raise the possibility that expanded repeat htt causes aberrant transcriptional regulation through its interaction with cellular transcription factors which may result in neuronal dysfunction and cell death in HD.

Animals↗
PubMed2000

Inhibition of huntingtin fibrillogenesis by specific antibodies and small molecules: implications for Huntington's disease therapy.

The accumulation of insoluble protein aggregates in intra and perinuclear inclusions is a hallmark of Huntington's disease (HD) and related glutamine-repeat disorders. A central question is whether protein aggregation plays a direct role in the pathogenesis of these neurodegenerative diseases. Here we show by using a filter retardation assay that the mAb 1C2, which specifically recognizes the elongated polyglutamine (polyQ) stretch in huntingtin, and the chemical compounds Congo red, thioflavine S, chrysamine G, and Direct fast yellow inhibit HD exon 1 protein aggregation in a dose-dependent manner. On the other hand, potential inhibitors of amyloid-beta formation such as thioflavine T, gossypol, melatonin, and rifampicin had little or no inhibitory effect on huntingtin aggregation in vitro. The results obtained by the filtration assay were confirmed by electron microscopy, SDS/PAGE, and MS. Furthermore, cell culture studies revealed that the Congo red dye at micromolar concentrations reduced the extent of HD exon 1 aggregation in transiently transfected COS cells. Together, these findings contribute to a better understanding of the mechanism of huntingtin fibrillogenesis in vitro and provide the basis for the development of new huntingtin aggregation inhibitors that may be effective in treating HD.

Animals↗
PubMed2000

Protein aggregation in Huntington's and Parkinson's disease: implications for therapy.

The accumulation of highly insoluble intracellular protein aggregates in neuronal inclusions is a hallmark of Huntington's disease (HD) and Parkinson's disease (PD) as well as several other late-onset neurodegenerative disorders. The aggregates formed in vitro and in vivo generally have a fibrillar morphology, consist of individual beta-strands and are resistant to proteolytic degradation. Although the causal relationship between aggregate formation and disease remains to be proven, the gradual deposition of mutant protein in neurons is consistent with the late-onset and progressive nature of symptoms. Recently, circumstantial evidence from mouse and Drosophila model systems suggests that abnormal protein folding and aggregation play a key role in the pathogenesis of both HD and PD. Therefore, a detailed understanding of the molecular mechanisms of protein aggregation and its effects on neuronal cell death could open new opportunities for therapy.

Animals↗
PubMed1999

Aggregation of truncated GST-HD exon 1 fusion proteins containing normal range and expanded glutamine repeats.

We have shown previously by electron microscopy that the purified glutathione S-transferase (GST)-Huntington's disease (HD) exon 1 fusion protein with 51 glutamine residues (GST-HD51) is an oligomer, and that site-specific proteolytic cleavage of this fusion protein results in the formation of insoluble more highly ordered protein aggregates with a fibrillar or ribbon-like morphology (E. Scherzinger et al. (1997) Cell 90, 549-558). Here we report that a truncated GST HD exon 1 fusion protein with 51 glutamine residues, which lacks the proline-rich region C-terminal to the polyglutamine (polyQ) tract (GST-HD51 delta P) self-aggregates into high-molecular-mass protein aggregates without prior proteolytic cleavage. Electron micrographs of these protein aggregates revealed thread-like fibrils with a uniform diameter of ca. 25 nm. In contrast, proteolytic cleavage of GST-HD51 delta P resulted in the formation of numerous clusters of high-molecular-mass fibrils with a different, ribbon-like morphology. These structures were reminiscent of prion rods and beta-amyloid fibrils in Alzheimer's disease. In agreement with our previous results with full-length GST-HD exon 1, the truncated fusion proteins GST-HD20 delta P and GST-HD30 delta P did not show any tendency to form more highly ordered structures, either with or without protease treatment.

Cloning, Molecular↗
PubMed1999

Self-assembly of polyglutamine-containing huntingtin fragments into amyloid-like fibrils: implications for Huntington's disease pathology.

Huntington's disease is a progressive neurodegenerative disorder caused by a polyglutamine [poly(Q)] repeat expansion in the first exon of the huntingtin protein. Previously, we showed that N-terminal huntingtin peptides with poly(Q) tracts in the pathological range (51-122 glutamines), but not with poly(Q) tracts in the normal range (20 and 30 glutamines), form high molecular weight protein aggregates with a fibrillar or ribbon-like morphology, reminiscent of scrapie prion rods and beta-amyloid fibrils in Alzheimer's disease. Here we report that the formation of amyloid-like huntingtin aggregates in vitro not only depends on poly(Q) repeat length but also critically depends on protein concentration and time. Furthermore, the in vitro aggregation of huntingtin can be seeded by preformed fibrils. Together, these results suggest that amyloid fibrillogenesis in Huntington's disease, like in Alzheimer's disease, is a nucleation-dependent polymerization.

Amino Acid Sequence↗
PubMed1999

Huntington's disease intranuclear inclusions contain truncated, ubiquitinated huntingtin protein.

Intranuclear inclusion bodies are a shared pathological feature of Huntington's disease (HD) and its transgenic mouse model. Using a panel of antibodies spanning the entire huntingtin molecule, we have investigated the pattern of immunoreactivity within the intranuclear inclusions in the frontal cortex and striatum of patients with HD. The intranuclear inclusions reacted with anti-ubiquitin and antibodies against the N-terminal portion of huntingtin (CAG53b, HP1), but not with HD1 and the 1C2 antibodies that detect the expanded polyglutamine tract nor the more C-terminal antibodies. However, the 1C2, HP1, CAG53b, and HD1 antibodies detected granular cytoplasmic deposits in cortical and striatal neurons that also contained intranuclear N-terminal huntingtin immunoreactivity. These data show a differential intracellular location of truncated huntingtin in the HD brain. Both the cytoplasmic and the nuclear aggregates of the protein fragments could be neurotoxic. The frequency of the cortical intranuclear inclusions correlated with the size of CAG expansion and was inversely related to the age at onset and death. No such correlations were detected for the striatum, which most likely reflects a more advanced neuronal loss accrued by the time of death.

Adult↗
PubMed1999

Folding of oligoglutamines: a theoretical approach based upon thermodynamics and molecular mechanics.

Folding of oligoglutamine chains of different lengths is of crucial interest for exploring the molecular mechanisms of Huntington's disease. A simple oligoglutamine model based upon the Flory-Huggins theory of polymer solutions demonstrates a random coil instability in chains containing more than 40 glutamine residues with respect to beta-sheet formation. This is in striking quantitative agreement with biochemical results on the chain length dependence of polyglutamine aggregation in vivo and in vitro, as well as with clinical data on the polyglutamine chain length dependence of the onset of Huntington's disease. Furthermore, a detailed molecular-mechanical investigation of a polypeptide chain carrying 40 glutamine residues was performed. Two possible folding modes of such an oligoglutamine chain were revealed: a) a beta-hairpin and b) a highly compact random coil entity stabilized by a wealth of H-bonds among the glutamine side chains. A possible role of these folding modes in polyglutamine aggregation, as well as in the onset of Huntington's disease, is discussed.

Amino Acid Sequence↗
PubMed1999

Formation of polyglutamine inclusions in non-CNS tissue.

Huntington's disease (HD) is one of a class of inherited progressive neurodegenerative disorders that are caused by a CAG/polyglutamine repeat expansion. We have previously generated mice that are transgenic for exon 1 of the HD gene carrying highly expanded CAG repeats which develop a progressive movement disorder and weight loss with similarities to HD. Neuronal inclusions composed of the exon 1 protein and ubiquitin are present in specific brain regions prior to onset of the phenotype, which in turn occurs long before specific neurodegeneration can be detected. In this report we have extended the search for polyglutamine inclusions to non-neuronal tissues. Outside the central nervous system (CNS), inclusions were identified in a variety of post-mitotic cells. This is consistent with a concentration-dependent nucleation and aggregation model of inclusion formation and indicates that brain-specific factors are not necessary for this process. To possibly gain insights into the wasting that is observed in the human disease, we have conducted a detailed analysis of the timing and progression of inclusion formation in skeletal muscle and an investigation into the cause of the severe muscle atrophy that occurs in the mouse model. The formation of inclusions in non-CNS tissues will be particularly useful with respect to in vivo monitoring of pharmaceutical agents selected for their ability to prevent polyglutamine aggregation in vitro, without the requirement that the agent can cross the blood-brain barrier in the first instance.

Animals↗