The Relationship between Parkin and Protein Aggregation in Neurodegenerative Diseases

The most prominent changes in neurodegenerative diseases are protein accumulation and inclusion formation. Several neurodegenerative diseases, including Alzheimer's, the Synucleinopathies and Tauopathies share several overlapping clinical symptoms manifest in Parkinsonism, cognitive decline and dementia. As degeneration progresses in the disease process, clinical symptoms suggest convergent pathological pathways. Biochemically, protein cleavage, ubiquitination and phosphorylation seem to play fundamental roles in protein aggregation, inclusion formation and inflammatory responses. In the following we provide a synopsis of the current knowledge about protein accumulation and astrogliosis as a common denominator in neurodegenerative diseases, and we propose insights into protein degradation and anti-inflammation. We review the E3-ubiquitin ligase and other possible functions of parkin as a suppressant of inflammatory signs and a strategy to clear amyloid proteins in neurodegenerative diseases

An AICD-based functional screen to identify APP metabolism regulators

<p>Abstract</p> <p>Background</p> <p>A central event in Alzheimer's disease (AD) is the regulated intramembraneous proteolysis of the β-amyloid precursor protein (APP), to generate the β-amyloid (Aβ) peptide and the APP intracellular domain (AICD). Aβ is the major component of amyloid plaques and AICD displays transcriptional activation properties. We have taken advantage of AICD transactivation properties to develop a genetic screen to identify regulators of APP metabolism. This screen relies on an APP-Gal4 fusion protein, which upon normal proteolysis, produces AICD-Gal4. Production of AICD-Gal4 induces Gal4-UAS driven luciferase expression. Therefore, when regulators of APP metabolism are modulated, luciferase expression is altered.</p> <p>Results</p> <p>To validate this experimental approach we modulated α-, β-, and γ-secretase levels and activities. Changes in AICD-Gal4 levels as measured by Western blot analysis were strongly and significantly correlated to the observed changes in AICD-Gal4 mediated luciferase activity. To determine if a known regulator of APP trafficking/maturation and Presenilin1 endoproteolysis could be detected using the AICD-Gal4 mediated luciferase assay, we knocked-down Ubiquilin 1 and observed decreased luciferase activity. We confirmed that Ubiquilin 1 modulated AICD-Gal4 levels by Western blot analysis and also observed that Ubiquilin 1 modulated total APP levels, the ratio of mature to immature APP, as well as PS1 endoproteolysis.</p> <p>Conclusion</p> <p>Taken together, we have shown that this screen can identify known APP metabolism regulators that control proteolysis, intracellular trafficking, maturation and levels of APP and its proteolytic products. We demonstrate for the first time that Ubiquilin 1 regulates APP metabolism in the human neuroblastoma cell line, SH-SY5Y.</p

Parkinson-related parkin reduces α-Synuclein phosphorylation in a gene transfer model

α-Synuclein aggregates in Lewy bodies and plays a central role in the pathogenesis of a group of neurodegenerative disorders, known as "Synucleinopathies", including Parkinson's disease. Parkin mutations result in loss of parkin E3-ubiquitin ligase activity and cause autosomal recessive early onset parkinsonism

Characterization of a Drosophila Alzheimer's Disease Model: Pharmacological Rescue of Cognitive Defects

Transgenic models of Alzheimer's disease (AD) have made significant contributions to our understanding of AD pathogenesis, and are useful tools in the development of potential therapeutics. The fruit fly, Drosophila melanogaster, provides a genetically tractable, powerful system to study the biochemical, genetic, environmental, and behavioral aspects of complex human diseases, including AD. In an effort to model AD, we over-expressed human APP and BACE genes in the Drosophila central nervous system. Biochemical, neuroanatomical, and behavioral analyses indicate that these flies exhibit aspects of clinical AD neuropathology and symptomology. These include the generation of Aβ40 and Aβ42, the presence of amyloid aggregates, dramatic neuroanatomical changes, defects in motor reflex behavior, and defects in memory. In addition, these flies exhibit external morphological abnormalities. Treatment with a γ-secretase inhibitor suppressed these phenotypes. Further, all of these phenotypes are present within the first few days of adult fly life. Taken together these data demonstrate that this transgenic AD model can serve as a powerful tool for the identification of AD therapeutic interventions

An AICD-based functional screen to identify APP metabolism regulators-3

<p><b>Copyright information:</b></p><p>Taken from "An AICD-based functional screen to identify APP metabolism regulators"</p><p>http://www.molecularneurodegeneration.com/content/2/1/15</p><p>Molecular Neurodegeneration 2007;2():15-15.</p><p>Published online 24 Aug 2007</p><p>PMCID:PMC2071909.</p><p></p>83-Gal4, and sAPPα levels compared to cells transfected with empty vector. (B) Quantification of Western blot densitometry in panel A. (C) ADAM17 transient over-expression significantly increases ADAM17, AICD-Gal4, C83-Gal4, and sAPPα levels. (D) Quantification of Western blot densitometry in panel C. (E) Transient over-expression of individual secretase genes increases AICD-Gal4 mediated luciferase activity. Luciferase was normalized to transfection efficiency, by dividing by luciferase activity. Individual secretase over-expression plasmids were co-transfected with pRL-SV40 plasmid, expressing luciferase. Bars represent the mean normalized luciferase activity of four independent trials and error bars represent standard errors. Statistical significance was determined using two-sample, one-tail t-tests to compare each secretase gene with the empty vector, followed by sequential Bonferroni procedure to adjust for multiple comparisons. * indicates p < 0.05; ** indicates p < 0.01

An AICD-based functional screen to identify APP metabolism regulators-8

<p><b>Copyright information:</b></p><p>Taken from "An AICD-based functional screen to identify APP metabolism regulators"</p><p>http://www.molecularneurodegeneration.com/content/2/1/15</p><p>Molecular Neurodegeneration 2007;2():15-15.</p><p>Published online 24 Aug 2007</p><p>PMCID:PMC2071909.</p><p></p>lls. (B) Ubiquilin 1 over-expression increases PS1 CTF levels in SY5Y-APP-Gal4 cells

Characterization of human lysophospholipid acyltransferase 3[S]

Esterifying lysophospholipids may serve a variety of functions, including phospholipid remodeling and limiting the abundance of bioactive lipids. Recently, a yeast enzyme, Lpt1p, that esterifies an array of lysophospholipids was identified. Described here is the characterization of a human homolog of LPT1 that we have called lysophosphatidylcholine acyltransferase 3 (LPCAT3). Expression of LPCAT3 in Sf9 insect cells conferred robust esterification of lysophosphatidylcholine in vitro. Kinetic analysis found apparent cooperativity with a saturated acyl-CoA having the lowest K0.5 (5 μM), a monounsaturated acyl-CoA having the highest apparent Vmax (759 nmol/min/mg), and two polyunsaturated acyl-CoAs showing intermediate values. Lysophosphatidylethanolamine and lysophosphatidylserine were also utilized as substrates. Electrospray ionization mass spectrometric analysis of phospholipids in Sf9 cells expressing LPCAT3 showed a relative increase in phosphatidylcholine containing saturated acyl chains and a decrease in phosphatidylcholine containing unsaturated acyl chains. Targeted reduction of LPCAT3 expression in HEK293 cells had essentially an opposite effect, resulting in decreased abundance of saturated phospholipid species and more unsaturated species. Reduced LPCAT3 expression resulted in more apoptosis and distinctly fewer lamellipodia, suggesting a necessary role for lysophospholipid esterification in maintaining cellular function and structure