Synuclein Deficiency Decreases the Efficiency of Dopamine Uptake by Synaptic Vesicles.

In the present study, we analyzed the uptake of radiolabeled dopamine by intact synaptosomes and purified synaptic vesicles isolated from the dorsal striatum of mice with constitutive inactivation of all three synuclein-coding genes and wild-type mice. Synuclein deficiency substantially compromised the uptake of this neurotransmitter by synaptic vesicles but had no effect on synaptosomal dopamine uptake.

Gamma-Carbolines Derivatives As Promising Agents for the Development of Pathogenic Therapy for Proteinopathy.

Uncontrolled protein aggregation, accompanied by the formation of specific inclusions, is a major component of the pathogenesis of many common neurodegenerative diseases known as proteinopathies. The intermediate products of this aggregation are toxic to neurons and may be lethal. The development strategy of pathogenic therapy for proteinopathy is based on the design of drugs capable of both inhibiting proteinopathy progression and increasing the survival of affected neurons. The results of a decade-long research effort at leading Russian and international laboratories have demonstrated that Dimebon (Latrepirdine), as well as a number of its derivatives from a gamma-carboline group, show a strong neuroprotective effect and can modulate the course of a neurodegenerative process in both in vitro and in vivo model systems. The accumulated data indicate that gamma-carbolines are promising compounds for the development of pathogenic therapy for proteinopathies.

Dimebon reduces the levels of aggregated amyloidogenic protein forms in detergent-insoluble fractions in vivo.

Aggregation of proteins liable to assembling into fibrils with subsequent formation of amyloid incorporations is an important component in the pathogenesis of many neurodegenerative diseases. Dimebon, a Russian drug, reduces the content of detergent-insoluble fibrillar forms of synuclein, the main protein component of pathological incorporations in neurons of transgenic mouse strain used in the study.

Deletion of alpha-synuclein decreases impulsivity in mice.

The presynaptic protein alpha-synuclein, associated with Parkinson's Disease (PD), plays a role in dopaminergic neurotransmission and is implicated in impulse control disorders (ICDs) such as drug addiction. In this study we investigated a potential causal relationship between alpha-synuclein and impulsivity, by evaluating differences in motor impulsivity in the 5-choice serial reaction time task (5-CSRTT) in strains of mice that differ in the expression of the alpha-synuclein gene. C57BL/6JOlaHsd mice differ from their C57BL/6J ancestors in possessing a chromosomal deletion resulting in the loss of two genes, snca, encoding alpha-synuclein, and mmrn1, encoding multimerin-1. C57BL/6J mice displayed higher impulsivity (more premature responding) than C57BL/6JOlaHsd mice when the pre-stimulus waiting interval was increased in the 5-CSRTT. In order to ensure that the reduced impulsivity was indeed related to snca, and not adjacent gene deletion, wild type (WT) and mice with targeted deletion of alpha-synuclein (KO) were tested in the 5-CSRTT. Similarly, WT mice were more impulsive than mice with targeted deletion of alpha-synuclein. Interrogation of our ongoing analysis of impulsivity in BXD recombinant inbred mouse lines revealed an association of impulsive responding with levels of alpha-synuclein expression in hippocampus. Expression of beta- and gamma-synuclein, members of the synuclein family that may substitute for alpha-synuclein following its deletion, revealed no differential compensations among the mouse strains. These findings suggest that alpha-synuclein may contribute to impulsivity and potentially, to ICDs which arise in some PD patients treated with dopaminergic medication.

Localization of synucleins in the mammalian cochlea.

Synucleins are widely expressed synaptic proteins within the central nervous system that have been implicated in such neurodegenerative disorders as Parkinson's disease. In this study, an initial characterization of all three synucleins, alpha-, beta-, and gamma-synuclein, within the cochlea was undertaken. Reverse transcriptase-polymerase chain reaction (PCR) demonstrated all three synuclein mRNA species within microdissected cochlear tissue. Quantitative PCR suggests that beta-synuclein is the most abundantly expressed form, followed by gamma- and then alpha-synuclein. Western blot analysis similarly demonstrates all three synuclein proteins within microdissected cochlear tissue. Immunofluorescence localizes the three synucleins predominantly to the efferent neuronal system at the efferent outer hair cell synapse, with some additional localization within the efferent tunnel-crossing fibers (alpha- and gamma-synuclein), spiral ganglion (beta-synuclein), inner spiral bundle (gamma-synuclein), and stria vascularis (alpha- > beta-synuclein). Developmentally, gamma-synuclein can be seen in the region of the outer hair cells by E19, while alpha- and beta-synuclein do not clearly appear there until approximately P10. Additional studies in a null-mutant gamma-synuclein mouse show no histological changes in the organ of Corti with normal hair cell and spiral ganglion cell counts, and normal ABR and DPOAE thresholds in wild-type vs mutant littermates. Together, these results localize synucleins to the efferent cholinergic neuronal auditory system, pointing to a role in normal auditory function, and raising the potential implications for their role in auditory neurodegenerative disorders. However, gamma-synuclein alone is not required for the development and maintenance of normal hearing through P21. Whether overlapping roles of the other synucleins help compensate for the loss of gamma-synuclein remains to be determined.

Expression of adaptor protein Ruk/CIN85 isoforms in cell lines of various tissue origins and human melanoma.

AIM: Development of monoclonal and polyclonal antibodies against recombinant GST-fused proteins including correspondingly N- and C-terminal parts of Ruk/CIN85 adaptor protein. Analysis of Ruk/CIN85 expression patterns in cell lines of various tissue origins and human melanoma. METHODS: Recombinant GST-fused fragments of Ruk/CIN85 were expressed in bacterial system and affinity purified. Monoclonal antibodies against SH3A domain of Ruk/CIN85 were produced using hybridoma technique. The specificity of generated antibodies was examined by ELISA. Polyclonal antibodies against C-terminal coiled-coil region of Ruk/CIN85 were affinity purified from serum of immunized rabbit. Expression patterns of Ruk/CIN85 isoforms and their subcellular localization in cell lines of various tissue origins and human melanoma samples were analyzed by immunoblotting, immunoprecipitation and immunofluorescence microcopy. RESULTS: Ruk/CIN85 is ubiquitously expressed SH3-containing adaptor/scaffold protein which plays important roles in signalling processes. N-terminal half of Ruk/CIN85 molecule, including three SH3 domains, and its C-terminal coiled-coil region were used as antigens to produce monoclonal and polyclonal antibodies, respectively. Hybridoma cell lines secreting monoclonal antibodies (mAbs) to SH3 fragment of Ruk/CIN85 were established. One of the mAbs was extensively characterized and designated as MISh-A1. It was shown that this mAb recognizes an epitope, which resides within first SH3A domain. Polyclonal anti-Ruks Abs affinity purified from serum of immunized rabbit specifically recognized main Ruk/CIN85 isoforms, both endogenous and recombinant, in lysates of HEK293 cells. Notably, produced Abs did not cross-react with CD2AP, the member of the same family of adaptor/scaffold proteins. Multiple molecular forms of Ruk/CIN85 with apparent molecular weights of 130, 80-85, 70-75, 50-56, 34-40 and 29 kD were detected in cell lyzates of NIH3T3, Cos1, L1210, HEK293, Ramos, HeLa S3, MDCK, C6, A549 and U937 using anti-Ruk antibodies. Oligomerization between p85 and p50-56 forms of Ruk/CIN85 was revealed in C6 and NIH3T3 cells, but not in HeLa S3 and HEK293 cells by immunoprecipitation using MISh-A1 antibody following anti-Ruk Western-blot analysis. Using immunofluorescent microscopy and anti-Ruk antibodies, endogenous Ruk-variates were found mostly in cytoplasm of C6, NIH3T3, HEK293 cells and at lower level - in nuclei. CONCLUSION: Patterns of Ruk/CIN85 molecular forms expression are cell-specific and determined by cellular context. Assembly of oligomeric complexes between p85 and p50-56 Ruk/CIN85 isoforms in C6 and NIH3T3 cells but not in HeLa S3 and HEK293 cells may reflect their specific biological roles in different cell lines. High level of full-length Rukl/CIN85 form expression was revealed in extracts of human melanoma samples. Abs described in this paper may prove useful in future studies of Ruk/CIN85 expression and function in normal and transformed cells.

Adaptor protein Ruk1 forms protein-protein complexes with endonuclease activity in HEK293 cells.

The structural and functional organization of the adaptor protein Ruk(1) is characterized by the presence of three SH3-domains at the N-terminus followed by Pro- and Ser-rich sequences and a C-terminal coiled-coil region. Multiple modules in the Ruk(1) structure involved in protein-protein interactions can provide for formation of ligand clusters with varied properties and subcellular location. To study the nature and biological role of such complexes, the recombinant protein Ruk(1) with a Glu-epitope at the C-terminus (Ruk(1) Glu-tagged) was purified from transfected HEK293 cells by affinity chromatography on protein G-Sepharose with covalently conjugated anti-Glu-tag antibodies. By SDS polyacrylamide gel electrophoresis with subsequent staining with silver, a set of minor bands in addition to the 85-kD Ruk(1) Glu-tagged was detected in the purified preparation of the recombinant protein. Proteins with affinity for nucleic acids were also revealed in the Ruk(1) Glu-tagged preparation by retardation of electrophoretic mobility of 32P-labeled oligodeoxyribonucleotides in gel. The Ruk(1) Glu-tagged preparation was also shown to hydrolyze both deoxyribonucleotides and plasmid DNA. ZnCl2 and heparin inhibited the DNAse activity. These findings suggest the presence of DNases associated with the Ruk(1) protein in HEK293 cells. Such complexes were isolated from lysates of HEK293 cells by chromatography on heparin-Sepharose. By elution with 0.5 and 1.0 M NaCl, two fractions with DNase activity and containing proteins with molecular weights of 83, 80, and 72 kD were obtained. The reaction was inhibited by ZnCl2 and heparin, and previous precipitation of Ruk-related proteins with anti-Ruk antibodies resulted in the exhaustion of nuclease activity. By immunoblotting with anti-Ruk antibodies, 83-kD protein immunologically related to the Ruk(1) protein was identified in the fractions. It was concluded that the adaptor protein Ruk(1) forms complexes with endonucleases in HEK293 cells.

Role of STAT3 and PI 3-kinase/Akt in mediating the survival actions of cytokines on sensory neurons.

The binding of cytokines to the gp130 receptor activates the STAT3, MEK/MAPK, and PI3K/Akt signalling pathways. To assess the relative importance of these pathways in promoting the survival of cytokine-dependent neurons, we conditionally inactivated STAT3 in mice and inhibited MEK, PI3K, and Akt in cultured neurons using pharmacological reagents and by expressing specific inhibitory proteins. Inactivation of STAT3 enhanced the death of the cytokine-dependent sensory neurons of the nodose ganglion in vivo and substantially reduced the response of these neurons to CNTF and LIF in vitro. LY294002, an inhibitor of PI3K, but not PD98059, an inhibitor of MEK, markedly reduced the response of these neurons to CNTF, as did dominant-negative PI3K, dominant-negative Akt, and overexpression of Ruk (a natural PI3K inhibitor). These results demonstrate that STAT3 and PI3K/Akt signalling play major roles in mediating the survival response of neurons to cytokines.

Role of PI 3-kinase, Akt and Bcl-2-related proteins in sustaining the survival of neurotrophic factor-independent adult sympathetic neurons.

By adulthood, sympathetic neurons have lost dependence on NGF and NT-3 and are able to survive in culture without added neurotrophic factors. To understand the molecular mechanisms that sustain adult neurons, we established low density, glial cell-free cultures of 12-wk rat superior cervical ganglion neurons and manipulated the function and/or expression of key proteins implicated in regulating cell survival. Pharmacological inhibition of PI 3-kinase with LY294002 or Wortmannin killed these neurons, as did dominant-negative Class IA PI 3-kinase, overexpression of Rukl (a natural inhibitor of Class IA PI 3-kinase), and dominant-negative Akt/PKB (a downstream effector of PI 3-kinase). Phospho-Akt was detectable in adult sympathetic neurons grown without neurotrophic factors and this was lost upon PI 3-kinase inhibition. The neurons died by a caspase-dependent mechanism after inhibition of PI 3-kinase, and were also killed by antisense Bcl-xL and antisense Bcl-2 or by overexpression of Bcl-xS, Bad, and Bax. These results demonstrate that PI 3-kinase/Akt signaling and the expression of antiapoptotic members of the Bcl-2 family are required to sustain the survival of adult sympathetic neurons.

Cerd4, third member of the d4 gene family: expression and organization of genomic locus.

Two members of the d4 family of presumptive transcription modulators, neuro-d4 (Neud4) and ubi-d4/Requiem (Req), have been characterized previously. We cloned and characterized the third member of this gene family, cer-d4 (Cerd4), from chicken and mouse cDNA libraries. The expression patterns of Cerd4 gene in both species are similar and more restricted than expression patterns of other two d4 genes. The main sites of Cerd4 expression are retina and cerebellum, where multiple transcripts could be detected. Two major types of Cerd4 proteins are a full-length isoform possessing all domains characteristic to the d4 family and truncated XZ isoform without C-terminal tandem of PHD fingers. The developmental kinetics of expression of these isoforms is different. The intron/exon structure of human Cerd4 gene is similar to that of neuro-d4 and ubi-d4/Requiem genes, but most introns of Cerd4 gene are much larger than the corresponding introns of the other two genes.

Chicken synucleins: cloning and expression in the developing embryo.

Synucleins comprise a family of small intracellular proteins that have recently attracted considerable attention because of their involvement in human diseases. Mutations of alpha-synuclein has been found in several families with hereditary early-onset Parkinson's disease and accumulation of this protein in characteristic cytoplasmic inclusions is a pathohistological hallmark of several neurodegenerative diseases that have been recently classified as 'alpha;-synucleinopathies' (reviewed in Brain Res. Bull. 50 (1999) 465; J. Neurosci. Res. 58 (1999) 120; Philos. Trans. R. Soc. Lond. Biol. Sci. 354 (1999) 1101; Brain Pathol. 9 (1999) 733). Aggregates of beta-synuclein and persyn (gamma-synuclein) also have been found in dystrophic neurites associated with Parkinson's and other neurodegenerative diseases (Proc. Natl. Acad. Sci. USA 96 (1999) 13450; and our unpublished observations). Moreover, persyn has been implicated in malignization of breast tumours (Cancer Res. 57 (1997) 759; Cancer Res. 59 (1999) 742; Hum. Mol. Genet. 7 (1998) 1417). All synucleins have distinct, although overlapping, patterns of expression in the embryonic, postnatal and adult mammalian nervous systems, suggesting important, although still not clear, biological functions in neuronal developing. Chicken embryo is a unique object for developmental studies that allows in vivo manipulations not always possible for mammalian embryos. Studies of synucleins expression in this model system could shed light on their functions in the developing nervous system. We cloned three chicken synucleins from the embryonic neural cDNA libraries and studied their expression in normal chicken embryonic tissues by Northern and in situ hybridization with specific probes. Our results demonstrate that primary structures and expression patterns of synucleins are similar in birds and mammals, suggesting that conserved function of synucleins is important for embryonic development of vertebrates.

Induction of neuronal death by alpha-synuclein.

The molecular and cellular mechanisms underlying neuronal loss in neurodegenerative diseases are unclear. It is generally thought that aggregation of mutated, abnormally modified or abnormally folded proteins leads to the accumulation of extracellular, intracellular or intranuclear deposits that severely compromise cell physiology, leading to the death of the affected neurons. However, there is growing evidence that neuronal apoptosis in the absence of obvious pathological deposits could have a serious impact on the pathogenesis of neurodegenerative diseases. alpha-Synuclein has been implicated in aetiology and pathogenesis of certain neurodegenerative diseases, although the precise role of this protein in neurodegeneration is uncertain. The normal functions of alpha-synuclein and other members of the synuclein family in the development and function of the nervous system also remain elusive. Here we show that overexpression of wild-type and mutant forms of alpha-synuclein in cultured neurons, but not the closely related persyn (gamma-synuclein), causes apoptosis. These findings suggest that abnormalities of alpha-synuclein metabolism could lead to the neuronal loss occurring in certain forms of neurodegeneration before the formation of characteristic pathological lesions.

Negative regulation of PI 3-kinase by Ruk, a novel adaptor protein.

Class I(A) phosphatidylinositol 3-kinase (PI 3-kinase) is a key component of important intracellular signalling cascades. We have identified an adaptor protein, Ruk(l), which forms complexes with the PI 3-kinase holoenzyme in vitro and in vivo. This interaction involves the proline-rich region of Ruk and the SH3 domain of the p85 alpha regulatory subunit of the class I(A) PI 3-kinase. In contrast to many other adaptor proteins that activate PI 3-kinase, interaction with Ruk(l) substantially inhibits the lipid kinase activity of the enzyme. Overexpression of Ruk(l) in cultured primary neurons induces apoptosis, an effect that could be reversed by co-expression of constitutively activated forms of the p110 alpha catalytic subunit of PI 3-kinase or its downstream effector PKB/Akt. Our data provide evidence for the existence of a negative regulator of the PI 3-kinase signalling pathway that is essential for maintaining cellular homeostasis. Structural similarities between Ruk, CIN85 and CD2AP/CMS suggest that these proteins form a novel family of adaptor molecules that are involved in various intracellular signalling pathways.

[Genomic organization of the murine neuro-d4 gene]. / Genomnaia organizatsiia gena neuro-d4 myshi.

As the first step toward obtaining the null mutation or knock out of the neuro-d4 gene, we isolated phages containing fragments of the gene from a mouse genomic library. The nucleotide sequence of a region of the gene more than 10 kb in size was determined.