Melatonin synthesis in the human pineal gland

Poster presentation: The mammalian pineal organ is a peripheral oscillator, depending on afferent information from the so-called master clock in the suprachiasmatic nuclei of the hypothalamus. One of the best studied outputs of the pineal gland is the small and hydrophobic molecule melatonin. In all vertebrates, melatonin is synthesized rhythmically with high levels at night, signalling the body the duration of the dark period. Changes or disruptions of melatonin rhythms in humans are related to a number of pathophysiological disorders, like Alzheimer's disease, seasonal affective disorder or the Smith-Magenis-Syndrome. To use melatonin in preventive or curative interferences with the human circadian system, a complete understanding of the generation of the rhythmic melatonin signal in the human pineal gland is essential. Melatonin biosynthesis is best studied in the rodent pineal gland, where the activity of the penultimate and rate-limiting enzyme, the arylalkylamine N-acetyltransferase (AA-NAT), is regulated on the transcriptional level, whereas the regulatory role of the ultimate enzymatic step, achieved by the hydroxyindole O-methyltransferase (HIOMT), is still under debate. In rodents, Aa-nat mRNA is about 100-fold elevated during the night in response to adrenergic stimulation of the cAMP-signalling pathway, with AA-NAT protein levels closely following this dynamics. In contrast, in all ungulates studied so far (cow, sheep), a post-transcriptional regulation of the AA-NAT is central to determine rhythmic melatonin synthesis. AA-NAT mRNA levels are constantly elevated, and lead to a constitutive up-regulation of AA-NAT protein, which is, however, rapidly degraded via proteasomal proteolysis during the day. AA-NAT proteolysis is only terminated upon the nocturnal increase in cAMP levels. Similar to ungulates, a post-transcriptional control of this enzyme seems evident in the pineal gland of the primate Macaca mulatta. Studies on the molecular basis of melatonin synthesis in the human being are sparse and almost exclusively based on phenomenological data, derived from non-invasive investigations. Yet the molecular mechanisms underlying the generation of the hormonal message of darkness can currently only be deciphered using autoptic material. We therefore analyzed in human post-mortem pineal tissue Aa-nat and Hiomt mRNA levels, AA-NAT and HIOMT enzyme activity, and melatonin levels for the first time simultaneously within tissue samples of the same specimen. Here presented data show the feasibility of this approach. Our results depict a clear diurnal rhythm in AA-NAT activity and melatonin content, despite constant values for Aa-nat and Hiomt mRNA, and for HIOMT activity. Notably, the here elevated AA-NAT activity during the dusk period does not correspond to a simultaneous elevation in melatonin content. It is currently unclear whether this finding may suggest a more important role of the ultimate enzyme in melatonin synthesis, the HIOMT, for rate-limiting the melatonin rhythm, as reported recently for the rodent pineal gland. Thus, our data support for the first time experimentally that post-transcriptional mechanisms are responsible for the generation of rhythmic melatonin synthesis in the human pineal gland

ATXN2-CAG42 sequesters PABPC1 into insolubility and induces FBXW8 in cerebellum of old ataxic knock-in mice

Spinocerebellar Ataxia Type 2 (SCA2) is caused by expansion of a polyglutamine encoding triplet repeat in the human ATXN2 gene beyond (CAG)31. This is thought to mediate toxic gain-of-function by protein aggregation and to affect RNA processing, resulting in degenerative processes affecting preferentially cerebellar neurons. As a faithful animal model, we generated a knock-in mouse replacing the single CAG of murine Atxn2 with CAG42, a frequent patient genotype. This expansion size was inherited stably. The mice showed phenotypes with reduced weight and later motor incoordination. Although brain Atxn2 mRNA became elevated, soluble ATXN2 protein levels diminished over time, which might explain partial loss-of-function effects. Deficits in soluble ATXN2 protein correlated with the appearance of insoluble ATXN2, a progressive feature in cerebellum possibly reflecting toxic gains-of-function. Since in vitro ATXN2 overexpression was known to reduce levels of its protein interactor PABPC1, we studied expansion effects on PABPC1. In cortex, PABPC1 transcript and soluble and insoluble protein levels were increased. In the more vulnerable cerebellum, the progressive insolubility of PABPC1 was accompanied by decreased soluble protein levels, with PABPC1 mRNA showing no compensatory increase. The sequestration of PABPC1 into insolubility by ATXN2 function gains was validated in human cell culture. To understand consequences on mRNA processing, transcriptome profiles at medium and old age in three different tissues were studied and demonstrated a selective induction of Fbxw8 in the old cerebellum. Fbxw8 is encoded next to the Atxn2 locus and was shown in vitro to decrease the level of expanded insoluble ATXN2 protein. In conclusion, our data support the concept that expanded ATXN2 undergoes progressive insolubility and affects PABPC1 by a toxic gain-of-function mechanism with tissuespecific effects, which may be partially alleviated by the induction of FBXW8

Axonal inclusions in spinocerebellar ataxia type 3

Protein aggregation is a major pathological hallmark of many neurodegenerative disorders including polyglutamine diseases. Aggregation of the mutated form of the disease protein ataxin-3 into neuronal nuclear inclusions is well described in the polyglutamine disorder spinocerebellar ataxia type 3 (SCA3 or Machado–Joseph disease), although these inclusions are not thought to be directly pathogenic. Neuropil aggregates have not yet been described in SCA3. We performed a systematic immunohistochemical study of serial thick sections through brains of seven clinically diagnosed and genetically confirmed SCA3 patients. Using antibodies against ataxin-3, p62, ubiquitin, the polyglutamine marker 1C2 as well as TDP-43, we analyzed neuronal localization, composition and distribution of aggregates within SCA3 brains. The analysis revealed widespread axonal aggregates in fiber tracts known to undergo neurodegeneration in SCA3. Similar to neuronal nuclear inclusions, the axonal aggregates were ubiquitinated and immunopositive for the proteasome and autophagy associated shuttle protein p62, indicating involvement of neuronal protein quality control mechanisms. Rare TDP-43 positive axonal inclusions were also observed. Based on the correlation between affected fiber tracts and degenerating neuronal nuclei, we hypothesize that these novel axonal inclusions may be detrimental to axonal transport mechanisms and thereby contribute to degeneration of nerve cells in SCA3

Perbandingan Pendekatan Tradisional dan Semantic Web untuk Akses Informasi Sebagai Penunjang Pengambilan Keputusan

Pengambilan keputusan pada dunia industry akan membutuhkan data teks, grafik dan juga bentuk data traditional lainnya. Dengan perkembangan teknologi informasi saat ini makasifat dari sumber informasi berkembang sehingga berjumlah sangat besar, keragaman jenis sumber informasi (sintaktik, struktur, semantic) dan data volume data semakin besar serta komplek

Parkinson Phenotype in Aged PINK1-Deficient Mice Is Accompanied by Progressive Mitochondrial Dysfunction in Absence of Neurodegeneration

Background Parkinson's disease (PD) is an adult-onset movement disorder of largely unknown etiology. We have previously shown that loss-of-function mutations of the mitochondrial protein kinase PINK1 (PTEN induced putative kinase 1) cause the recessive PARK6 variant of PD. Methodology/Principal Findings Now we generated a PINK1 deficient mouse and observed several novel phenotypes: A progressive reduction of weight and of locomotor activity selectively for spontaneous movements occurred at old age. As in PD, abnormal dopamine levels in the aged nigrostriatal projection accompanied the reduced movements. Possibly in line with the PARK6 syndrome but in contrast to sporadic PD, a reduced lifespan, dysfunction of brainstem and sympathetic nerves, visible aggregates of alpha-synuclein within Lewy bodies or nigrostriatal neurodegeneration were not present in aged PINK1-deficient mice. However, we demonstrate PINK1 mutant mice to exhibit a progressive reduction in mitochondrial preprotein import correlating with defects of core mitochondrial functions like ATP-generation and respiration. In contrast to the strong effect of PINK1 on mitochondrial dynamics in Drosophila melanogaster and in spite of reduced expression of fission factor Mtp18, we show reduced fission and increased aggregation of mitochondria only under stress in PINK1-deficient mouse neurons. Conclusion Thus, aging Pink1 -/- mice show increasing mitochondrial dysfunction resulting in impaired neural activity similar to PD, in absence of overt neuronal death

Stages in the development of Parkinson’s disease-related pathology

The synucleinopathy, idiopathic Parkinson’s disease, is a multisystem disorder that involves only a few predisposed nerve cell types in specific regions of the human nervous system. The intracerebral formation of abnormal proteinaceous Lewy bodies and Lewy neurites begins at defined induction sites and advances in a topographically predictable sequence. As the disease progresses, components of the autonomic, limbic, and somatomotor systems become particularly badly damaged. During presymptomatic stages 1–2, inclusion body pathology is confined to the medulla oblongata/pontine tegmentum and olfactory bulb/anterior olfactory nucleus. In stages 3–4, the substantia nigra and other nuclear grays of the midbrain and forebrain become the focus of initially slight and, then, severe pathological changes. At this point, most individuals probably cross the threshold to the symptomatic phase of the illness. In the end-stages 5–6, the process enters the mature neocortex, and the disease manifests itself in all of its clinical dimensions. Keywords Alpha-synuclein . Lewy bodies . Le