L-DOPA-induced signaling pathways and neuroepigenetic mechanisms in experimental Parkinsonism and dyskinesia

In patients with Parkinson’s disease (PD), the restoration of depleted striatal dopamine by chronic administration of its precursor, L-DOPA, results in the emergence of debilitating involuntary movements. This complication, termed L-DOPA-induced dyskinesia (LID), represents a limitation to the most efficacious treatment for PD motor symptoms. LID progressively increases in severity despite the continual ability of L-DOPA to alleviate parkinsonian symptoms, suggesting divergent mechanisms of action and the potential for therapeutic intervention. Utilizing an experimental mouse model of PD, the work presented within this thesis investigates the molecular alterations underlying LID. These studies reveal that L-DOPA administration results in pathological intracellular signaling and gene expression within striatal medium spiny neurons (MSNs) expressing the dopamine D1 receptor (D1R). Following L-DOPA administration, sensitized D1R signaling results in hyperactivity of the cyclic 3’-5’ adenosine monophosphate (cAMP)/ cAMP-dependent kinase (PKA)/ dopamine- and cAMP-regulated phosphoprotein of 32 kDA (DARPP-32) pathway. This exaggerated response results in excessive activation of the downstream extracellularregulated kinases 1 and 2 (ERK1/2) and mammalian target of rapamycin complex 1 (mTORC1) cascades, both of which are implicated in LID. These data also demonstrate that nuclear events mediated by mitogen- and stress-activated kinase 1 (MSK1), a direct ERK1/2 substrate, promote the induction of the transcription factor ΔFosB, which exacerbates LID. Furthermore, the concerted activity of MSK1 and DARPP-32 promotes histone H3K27me3S28p and the dissociation from transcription start sites of Rnf2, a Polycomb group protein that represses gene expression. These events are associated with an increase in transcription. Taken together, these studies support the idea that sensitized striatal D1R signaling promotes LID by excessive activation of intracellular signaling pathways and nuclear events promoting gene expression

Fur Facts

Does your fur get the delicate care it deserves and demands through the summer months? Cold storage, of course, is its best possible protection against moths. However, it may be safely stored at home if there are cautious and thorough hands to care for it

A high level disc controller

Includes bibliographical references.Since the emergence of the digital computer in the 1940s, computer architecture has been largely dictated by the requirements of mathematicians and scientists. Trends have thus been towards processing data as quickly and as accurately as possible. Even now, in the age of large scale integration culminating in the microprocessor, internal structures remain committed to these ideals. This is not surprising since the main users of computers are involved with data processing and scientific computing. The process control engineer, who turned to the digital computer to provide the support he required in his ever increasing strive towards automation, has had therefore to use these generalized computing structures. His basic requirements however, are somewhat different to those of the data processing manager or the scientific user. He has to contend with an inherent problem of synchronizing the computer to the real-world timing of his plants. He is far more interested in the response time of the computer to an external occurrence than he is to sheer 'number-crunching' power. Despite the trends in process control towards distributed computing, even the most advanced systems require a relatively large central processor. This processor is called upon to carry out a wide variety of different tasks most of which are 'requested' by external events. Multiprogramming facilities are therefore essential and are normally effected by means of a real-time operating system. One of the prime objectives of such a real time operating system is to permit the various programs to be run at the required time on some priority basis. In many cases these routines can be large - thus requiring access to backing storage. Traditionally the backing store, implemented by a moving-head disc for example is under the control of the real-time operating system. This can have serious consequences. If real-time requirements are to be met, transfer to and from the disc must be made as rapidly as possible. Also, in initiating and controlling such transfer, the computer is using time which otherwise could be avai1ab1e for useful, process-orientated work. With the rapid advancement of digital technology, the time is c1ear1y right to examine our present computer architecture. This dissertation explores the problem area previously discussed - the control over the bulk storage device in a real-time process-control computer system. It is proposed that a possible solution lies in the development of an intelligent backing-store controller. This essentially combines the conventional low-level backing store interface with a special purpose processor which handles all file routines. This dissertation demonstrates how such a structure can be implemented using current technology, and will evaluate its inherent advantages

Psychometric precision in phenotype definition is a useful step in molecular genetic investigation of psychiatric disorders

Affective disorders are highly heritable, but few genetic risk variants have been consistently replicated in molecular genetic association studies. The common method of defining psychiatric phenotypes in molecular genetic research is either a summation of symptom scores or binary threshold score representing the risk of diagnosis. Psychometric latent variable methods can improve the precision of psychiatric phenotypes, especially when the data structure is not straightforward. Using data from the British 1946 birth cohort, we compared summary scores with psychometric modeling based on the General Health Questionnaire (GHQ-28) scale for affective symptoms in an association analysis of 27 candidate genes (249 single-nucleotide polymorphisms (SNPs)). The psychometric method utilized a bi-factor model that partitioned the phenotype variances into five orthogonal latent variable factors, in accordance with the multidimensional data structure of the GHQ-28 involving somatic, social, anxiety and depression domains. Results showed that, compared with the summation approach, the affective symptoms defined by the bi-factor psychometric model had a higher number of associated SNPs of larger effect sizes. These results suggest that psychometrically defined mental health phenotypes can reflect the dimensions of complex phenotypes better than summation scores, and therefore offer a useful approach in genetic association investigations

Deciphering the Actions of Antiparkinsonian and Antipsychotic Drugs on cAMP/DARPP-32 Signaling

The basal ganglia are affected by several neuropsychiatric and neurodegenerative diseases, many of which are treated with drugs acting on the dopamine system. For instance, the loss of dopaminergic input to the striatum, which is the main pathological feature of Parkinson’s disease, is counteracted by administering the dopamine precursor, L-DOPA. Furthermore, psychotic disorders, including schizophrenia, are treated with drugs that act as antagonists at the D2-type of dopamine receptor (D2R). The use of L-DOPA and typical antipsychotic drugs, such as haloperidol, is limited by the emergence of motor side-effects, particularly after prolonged use. Striatal medium spiny neurons (MSNs) represent an ideal tool to investigate the molecular changes implicated in these conditions. MSNs receive a large glutamatergic innervation from cortex, thalamus, and limbic structures, and are controlled by dopaminergic projections originating in the midbrain. There are two large populations of striatal MSNs, which differ based on their connectivity to the output nuclei of the basal ganglia and on their ability to express dopamine D1 receptors (D1Rs) or D2Rs. Administration of L-DOPA promotes cAMP signaling and activates the dopamine- and cAMP-regulated phosphoprotein of 32 kDa (DARPP-32) in the D1R-expressing MSNs, which form the striatonigral, or direct pathway. Conversely, haloperidol activates the cAMP/DARPP-32 cascade in D2R-expressing MSNs, which form the striatopallidal, or indirect pathway. This review describes the effects produced on downstream effector proteins by stimulation of cAMP/DARPP-32 signaling in these two groups of MSNs. Particular emphasis is given to the regulation of the GluR1 subunit of the α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate glutamate receptor, the extracellular signal-regulated protein kinases 1 and 2, focusing on functional role and potential pathological relevance

Portraits of resilience : writing a socio-cultural history of a black South African location with the Ngilima photographic collection. Benoni, 1950s-1960s.

  This thesis engages with the ongoing debate regarding how photographs can contribute to the writing of black South African history. In the field of South African visual history, a significant literature explores the “white gaze” that emanates from the administrative and missionary photographic archives of the colonial period. Comparatively fewer studies, however, have addressed how black South Africans pictured themselves, largely due to the presumption that black visual archives are scarce and difficult to access. This thesis draws upon previously unexplored photographic evidence from the mid twentieth century—intimate photographs found in black homes. I argue that these images constitute an alternative archive and original source of history. Such archives present a radically different perspective on black urban communities than that emanating from public photographic collections. Photographic portraiture translates how black South Africans wanted to be seen, according to their own conventions. To study everyday photographic practices is to reflect on the set of values, attitudes and ideas that influenced this exercise of self-representation. This thesis employs a variety of methods and approaches—photo elicitation, identifying patterns in poses and conventions, scrutinizing background details, and locating photographs in today’s landscape—to help unravel the historical relevance of seemingly mundane images.  Colonial and Global Histor

Impaired Associative Fear Learning in Mice with Complete Loss or Haploinsufficiency of AMPA GluR1 Receptors

There is compelling evidence that l-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) glutamate receptors containing the GluR1 subunit contribute to the molecular mechanisms associated with learning. AMPA GluR1 glutamate receptor knockout mice (KO) exhibit abnormal hippocampal and amygdala plasticity, and deficits on various assays for cognition including Pavlovian fear conditioning. Here we examined associative fear learning in mice with complete absence (KO) or partial loss (heterozygous mutant, HET) of GluR1 on multiple fear conditioning paradigms. After multi-trial delay or trace conditioning, KO displayed impaired tone and context fear recall relative to WT, whereas HET were normal. After one-trial delay conditioning, both KO and HET showed impaired tone and context recall. HET and KO showed normal nociceptive sensitivity in the hot plate and tail flick tests. These data demonstrate that the complete absence of GluR1 subunit-containing receptors prevents the formation of associative fear memories, while GluR1 haploinsufficiency is sufficient to impair one-trial fear learning. These findings support growing evidence of a major role for GluR1-containing AMPA receptors in amygdala-mediated forms of learning and memory

L-DOPA-Induced Dyskinesia and Abnormal Signaling in Striatal Medium Spiny Neurons: Focus on Dopamine D1 Receptor-Mediated Transmission

Dyskinesia is a serious motor complication caused by prolonged administration of l-DOPA to patients affected by Parkinson’s disease. Accumulating evidence indicates that l-DOPA-induced dyskinesia (LID) is primarily caused by the development of sensitized dopamine D1 receptor (D1R) transmission in the medium spiny neurons (MSNs) of the striatum. This phenomenon, combined with chronic administration of l-DOPA, leads to persistent and intermittent hyper-activation of the cAMP signaling cascade. Activation of cAMP signaling results in increased activity of the cAMP-dependent protein kinase (PKA) and of the dopamine- and cAMP-dependent phosphoprotein of 32 kDa (DARPP-32), which regulate several downstream effector targets implicated in the control of the excitability of striatal MSNs. Dyskinesia is also accompanied by augmented activity of the extracellular signal-regulated kinases (ERK) and the mammalian target of rapamycin complex 1 (mTORC1), which are involved in the control of transcriptional and translational efficiency. Pharmacological or genetic interventions aimed at reducing abnormal signal transduction at the level of these various intracellular cascades have been shown to attenuate LID in different animal models. For instance, LID is reduced in mice deficient for DARPP-32, or following inhibition of PKA. Blockade of ERK obtained genetically or using specific inhibitors is also able to attenuate dyskinetic behavior in rodents and non-human primates. Finally, administration of rapamycin, a drug which blocks mTORC1, results in a strong reduction of LID. This review focuses on the abnormalities in signaling affecting the D1R-expressing MSNs and on their potential relevance for the design of novel anti-dyskinetic therapies

Emerging roles of the mitogen and stress activated kinases MSK1 and MSK2

Mitogen- and stress-activated kinases (MSK) 1 and 2 are nuclear proteins activated downstream of the ERK1/2 or p38 MAPK pathways. MSKs phosphorylate multiple substrates, including CREB and Histone H3, and their major role is the regulation of specific subsets of Immediate Early genes (IEG). While MSKs are expressed in multiple tissues, their levels are high in immune and neuronal cells and it is in these systems most is known about their function. In immunity, MSKs have predominantly anti-inflammatory roles and help regulate production of the anti-inflammatory cytokine IL-10. In the CNS they are implicated in neuronal proliferation and synaptic plasticity. In this review we will focus on recent advances in understanding the roles of MSKs in the innate immune system and neuronal function

Membrane Trafficking in the Yeast Saccharomyces cerevisiae Model

International audienceThe yeast Saccharomyces cerevisiae is one of the best characterized eukaryotic models. The secretory pathway was the first trafficking pathway clearly understood mainly thanks to the work done in the laboratory of Randy Schekman in the 1980s. They have isolated yeast sec mutants unable to secrete an extracellular enzyme and these SEC genes were identified as encoding key effectors of the secretory machinery. For this work, the 2013 Nobel Prize in Physiology and Medicine has been awarded to Randy Schekman; the prize is shared with James Rothman and Thomas Südhof. Here, we present the different trafficking pathways of yeast S. cerevisiae. At the Golgi apparatus newly synthesized proteins are sorted between those transported to the plasma membrane (PM), or the external medium, via the exocytosis or secretory pathway (SEC), and those targeted to the vacuole either through endosomes (vacuolar protein sorting or VPS pathway) or directly (alkaline phosphatase or ALP pathway). Plasma membrane proteins can be internalized by endocytosis (END) and transported to endosomes where they are sorted between those targeted for vacuolar degradation and those redirected to the Golgi (recycling or RCY pathway). Studies in yeast S. cerevisiae allowed the identification of most of the known effectors, protein complexes, and trafficking pathways in eukaryotic cells, and most of them are conserved among eukaryotes