γ-synuclein is a novel player in the control of body lipid metabolism

Peer reviewedPublisher PD

Modulation of α-synuclein expression in transgenic animals for modelling synucleinopathies — is the juice worth the squeeze?

Studies of various animal models have made a substantial contribution to the recent progress in understanding the molecular and cellular basis of neurodegenerative disorders. Modelling of neuro-degeneration by genetic alteration of laboratory animals became one of the most powerful tools of modern experimental neurology. The crucial event in pathogenesis of neurodegenerative diseases known as synucleinopathies is modification of α-synuclein metabolism caused by missense mutations, increased expression of the gene, or impaired degradation or intracellular compart-mentalisation of the protein. Therefore, manipulations with expression of α-synuclein in laboratory animals were widely used for creating models of these diseases. In the present review we discuss strong and weak sides of such models, what has been already learned from studies of these animals and what types of models might be useful to further our knowledge about pathogenesis of different synucleinopathies

Modulation of p-eIF2α cellular levels and stress granule assembly/disassembly by trehalose

Stress granules (SGs) are an important component of cellular stress response. Compromised assembly of SGs as well as their premature or delayed disassembly affect physiology and survival of cells under stress or during recovery from stress. Consequently, abnormal turnover of SGs has been implicated in the development of various pathologies, including neurodegeneration. We found that pretreatment of cells with a natural disaccharide trehalose, a known autophagy enhancer, delays SG assembly and facilitates their premature post-stress disassembly. Mechanistically, the effect of trehalose on SGs is mediated via the p-eIF2α rather than autophagosome pathway. Trehalose increases pre-stress levels of p-eIF2α and its phosphatase subunits and promotes post-stress translational recovery. Upon prolonged treatment, trehalose impairs basal translation affecting production of transiently expressed proteins. Early translational recovery and SG disassembly induced by trehalose pretreatment can sensitise cells to stress and impair survival. Our study has important implications for the use of trehalose in studies of autophagic clearance of misfolded proteins and for targeting SGs as a possible therapeutic approach in neurodegenerative and other diseases

Combinational losses of synucleins reveal their differential requirements for compensating age-dependent alterations in motor behavior and dopamine metabolism

Synucleins are involved in multiple steps of the neurotransmitter turnover but the largely normal synaptic function in young adult animals completely lacking synucleins suggests their roles are dispensable for execution of these processes. Instead, they may be utilized for boosting the efficiency of certain molecular mechanisms in presynaptic terminals, with a deficiency of synuclein proteins sensitizing to or exacerbating synaptic malfunction caused by accumulation of mild alterations, which are commonly associated with aging. Although functional redundancy within the family has been reported, it is unclear whether the remaining synucleins can fully compensate for the deficiency of a lost family member, or whether some functions are specific for a particular member. We assessed several structural and functional characteristics of the nigrostriatal system of mice lacking members of the synuclein family in every possible combination and demonstrated that stabilization of the striatal dopamine level depends on the presence of α-synuclein and cannot be compensated for by other family members, whereas β-synuclein is required for efficient maintenance of animal’s balance and coordination in old age

Frameshift peptides alter the properties of truncated FUS proteins in ALS-FUS

Mutations in the FUS gene cause a subset of ALS cases (ALS-FUS). The majority of FUS mutations are missense mutations affecting the nuclear localisation signal (NLS) of FUS. In addition, a number of frameshift mutations which result in complete NLS deletion have been described. Patients bearing frameshift mutations usually present with more aggressive disease, characterised by an early onset and rapid progression. Both missense mutations in the NLS coding sequence and complete loss of the NLS are known to result in cytoplasmic mislocalisation of FUS protein. However, in addition to the removal of FUS functional domains, frameshift mutations in most cases lead to the attachment of a “tail” of novel amino acids at the FUS C-terminus – a frameshift peptide. It is not clear whether these peptide tails would affect the properties of truncated FUS proteins. In the current study, we compared intracellular behaviour of disease-associated truncated FUS proteins with and without the corresponding frameshift peptides. We demonstrate that some of these peptides can affect subcellular distribution and/or increase aggregation capacity and stability of the truncated FUS protein. Our study suggests that frameshift peptides can alter the properties of truncated FUS variants which may modulate FUS pathogenicity and contribute to the variability of the disease course in ALS-FUS

Molecular cloning and expression pattern of rpr-1, a resiniferatoxin-binding, phosphotriesterase-related protein, expressed in rat kidney tubules1The sequence of rpr-1 has the EMBL accession number X99477.1

AbstractBacterial phosphotriesterases are enzymes that hydrolyse phosphotriester-containing organophosphate pesticides. Resiniferatoxin is a vanilloid that desensitises nociceptive neurons. By screening a rat cDNA library with labelled resiniferatoxin, we unexpectedly isolated a novel rat phosphotriesterase homologue, here named rpr-1, that encodes a 349 amino acid, 39 kDa protein (confirmed by in vitro translation). Northern blotting and in situ hybridisation show expression primarily in proximal tubules of the kidney, in which rpr-1 distribution correlates with resiniferatoxin-binding activity. These results suggest an unsuspected link between the phosphotriesterase enzyme family and resiniferatoxin toxicity and pharmacology

Reduced complement of dopaminergic neurons in the substantia nigra pars compacta of mice with a constitutive “low footprint” genetic knockout of alpha-synuclein

Previous studies of the alpha-synuclein null mutant mice on the C57Bl6 genetic background have revealed reduced number of dopaminergic neurons in their substantia nigra pars compacta (SNpc). However, the presence in genomes of the studied mouse lines of additional genetic modifications that affect expression of genes located in a close proximity to the alpha-synuclein-encoding Snca gene makes these data open to various interpretations. To unambiguously demonstrate that the absence of alpha-synuclein is the primary cause of the observed deficit of dopaminergic neurons, we employed a recently produced constituent alpha-synuclein knockout mouse line B6(Cg)-Sncatm1.2Vlb/J. The only modification introduced to the genome of these mice is a substitution of the first coding exon and adjusted short intronic fragments of the Snca gene by a single loxP site. We compared the number of dopaminergic neurons in the SNpc of this line, previously studied B6(Cg)-Sncatm1Rosl/J line and wild type littermate mice. A similar decrease was observed in both knockout lines when compared with wild type mice. In a recently published study we revealed no loss of dopaminergic neurons following conditional inactivation of the Snca gene in neurons of adult mice. Taken together, these results strongly suggest that alpha-synuclein is required for efficient survival or maturation of dopaminergic neurons in the developing SNpc but is dispensable for survival of mature SNpc dopaminergic neurons

Synuclein deficiency results in age-related respiratory and cardiovascular dysfunctions in mice

Synuclein (α, β, and γ) proteins are highly expressed in presynaptic terminals, and significant data exist supporting their role in regulating neurotransmitter release. Targeting the gene encoding α-synuclein is the basis of many animal models of Parkinson’s disease (PD). However, the physiological role of this family of proteins in not well understood and could be especially relevant as interfering with accumulation of α-synuclein level has therapeutic potential in limiting PD progression. The long-term effects of their removal are unknown and given the complex pathophysiology of PD, could exacerbate other clinical features of the disease, for example dysautonomia. In the present study, we sought to characterize the autonomic phenotypes of mice lacking all synucleins (α, β, and γ; αβγ−/−) in order to better understand the role of synuclein-family proteins in autonomic function. We probed respiratory and cardiovascular reflexes in conscious and anesthetized, young (4 months) and aged (18–20 months) αβγ−/− male mice. Aged mice displayed impaired respiratory responses to both hypoxia and hypercapnia when breathing activities were recorded in conscious animals using whole-body plethysmography. These animals were also found to be hypertensive from conscious blood pressure recordings, to have reduced pressor baroreflex gain under anesthesia, and showed reduced termination of both pressor and depressor reflexes. The present data demonstrate the importance of synuclein in the normal function of respiratory and cardiovascular reflexes during aging

Generation of mouse lines with conditionally or constitutively inactivated Snca gene and Rosa26-stop-lacZ reporter located in cis on the mouse chromosome 6

α-Synuclein is involved in many important molecular processes in neuronal cells and their synapses, and its malfunction has been linked to the development of Parkinson’s and certain other neurodegenerative diseases. Animal models allowing tightly monitored conditional inactivation of the encoding gene, Snca, are indispensible for studies aimed at understanding normal function of α-synuclein in various neuronal populations and its role in pathogenesis of neurodegenerative diseases. We have recently reported the production of several novel mouse lines for manipulating expression of the endogenous Snca gene, including a line for Cre-recombinase-driven conditional inactivation of the gene (mice with floxed Snca) and a new line with a constitutive knockout of α-synuclein. Rosa26-stop-lacZ reporter cassette is commonly used for monitoring efficiency of Cre-recombination but in mouse genome Snca and Rosa26 loci are located on the same chromosome. Here we describe production of lines with a modified Snca locus, either floxed or constitutively inactivated and the Rosa26-stop-lacZ reporter cassette located in cis on the mouse chromosome 6. These new mouse lines are invaluable for fast identification of cells with inactivation of Snca by Cre-recombination and represent useful tools for in vivo studies of α-synuclein function and dysfunctio

Kinetics of alpha-synuclein depletion in three brain regions following conditional pan-neuronal inactivation of the encoding gene (Snca) by tamoxifen-induced Cre-recombination in adult mice

Conditional pan-neuronal inactivation of the Snca gene in 2-month old male and female mice causes dramatic decrease in the level of the encoded protein, alpha-synuclein, in three studied brain regions, namely cerebral cortex, midbrain and striatum, 12 weeks after the last injection of tamoxifen. Kinetics of alpha-synuclein depletion is different in these brain regions with a longer lag period in the cerebral cortex where this protein is normally most abundant. Our results suggest that efficient post-developmental pan-neuronal knockout of alpha-synuclein in adult, i.e. 5- to 6-month old, animals, could be achieved by tamoxifen treatment of 2-month old mice carrying loxP-flanked Snca gene and expressing inducible Cre-ERT2 recombinase under control of the promoter of neuron-specific enolase (NSE) gene