MAB2510 Sigma-AldrichAnti-Green Fluorescent Protein Antibody, original GFP only, clone 264-449-2

Protein phosphatase 2A (PP2A) holoenzyme is a heterotrimeric complex, consisting of A, B and C subunits. The catalytic subunit PP2A-C (microtubule star/mts) binds to the C-terminal part of the scaffold protein PP2A-A (PP2A-29B). In Drosophila, there are three different forms of B subunits (widerborst/wdb, twins/tws and PP2A-B'), which determine the subcellular localization and substrate specificity of the holoenzyme. Previous studies demonstrated that PP2A is involved in the control of TOR-dependent autophagy both in yeast and mammals. Furthermore, in Drosophila, wdb genetically interacts with the PtdIns3K/PTEN/Akt signaling cascade, which is a main upstream regulatory system of dTOR. Here we demonstrate that in Drosophila, two different PP2A complexes (containing B' or wdb subunit) play essential roles in the regulation of starvation-induced autophagy. The PP2A-A/wdb/C complex acts upstream of dTOR, whereas the PP2A-A/B'/C complex functions as a target of dTOR and may regulate the elongation of autophagosomes and their subsequent fusion with lysosomes. We also identified three Drosophila Atg orthologs (Atg14, Atg17 and Atg101), which represent potential targets of the PP2A-A/B'/C complex during autophagy.

Defects in cellular energy metabolism represent an early feature in a variety of human neurodegenerative diseases. Recent studies have shown that targeting energy metabolism can protect against neuronal cell death in such diseases. Here, we show that meclizine, a clinically used drug that we have recently shown to silence oxidative metabolism, suppresses apoptotic cell death in a murine cellular model of polyglutamine (polyQ) toxicity. We further show that this protective effect extends to neuronal dystrophy and cell death in Caenorhabditis elegans and Drosophila melanogaster models of polyQ toxicity. Meclizine's mechanism of action is not attributable to its anti-histaminergic or anti-muscarinic activity, but rather, strongly correlates with its ability to suppress mitochondrial respiration. Since meclizine is an approved drug that crosses the blood-brain barrier, it may hold therapeutic potential in the treatment of polyQ toxicity disorders, such as Huntington's disease.

In addition to the hallmark neurological manifestations of Huntington's disease (HD), weight loss with metabolic dysfunction is often observed in the later stages of disease progression and is associated with poor prognosis. The mechanism for weight loss in HD is unknown. Using two mouse models of HD, the R6/2 transgenic and CAG140 knock-in mouse strains, we demonstrate that adipose tissue dysfunction is detectable at early ages and becomes more pronounced as the disease progresses. Adipocytes acquire a 'de-differentiated' phenotype characterized by impaired expression of fat storage genes. In addition, HD mice exhibit reduced levels of leptin and adiponectin, adipose tissue-derived hormones that regulate food intake and glucose metabolism. Importantly, some of these changes occur prior to weight loss and development of some of the characteristic neurological symptoms. We demonstrate that impaired gene expression and lipid accumulation in adipocytes can be recapitulated by expression of an inducible mutant huntingtin transgene in an adipocyte cell line and that mutant huntingtin inhibits transcriptional activity of the PGC-1alpha co-activator in adipocytes, which may contribute to aberrant gene expression. Thus, our findings indicate that mutant huntingtin has direct detrimental effects in cell types other than neurons. The results also indicate that circulating adipose-tissue-derived hormones may be accessible markers for HD prognosis and progression and suggest that adipose tissue may be a useful therapeutic target to improve standard of life for HD patients.

Increasing evidence indicates the importance of neuron-glia communication for synaptic function, but the mechanisms involved are not fully understood. We reported that the EphA4 receptor tyrosine kinase is in dendritic spines of pyramidal neurons of the adult hippocampus and regulates spine morphology. We now show that the ephrin-A3 ligand, which is located in the perisynaptic processes of astrocytes, is essential for maintaining EphA4 activation and normal spine morphology in vivo. Ephrin-A3-knockout mice have spine irregularities similar to those observed in EphA4-knockout mice. Remarkably, loss of ephrin-A3 or EphA4 increases the expression of glial glutamate transporters. Consistent with this, glutamate transport is elevated in ephrin-A3-null hippocampal slices whereas Eph-dependent stimulation of ephrin-A3 signaling inhibits glutamate transport. Furthermore, some forms of hippocampus-dependent learning are impaired in the ephrin-A3-knockout mice. Our results suggest that the interaction between neuronal EphA4 and glial ephrin-A3 bidirectionally controls synapse morphology and glial glutamate transport, ultimately regulating hippocampal function.

Aggregated alpha-synuclein (alpha-syn) fibrils form Lewy bodies (LBs), the signature lesions of Parkinson's disease (PD) and related synucleinopathies, but the pathogenesis and neurodegenerative effects of LBs remain enigmatic. Recent studies have shown that when overexpressed in Saccharomyces cerevisiae, alpha-syn localizes to plasma membranes and forms cytoplasmic accumulations similar to human alpha-syn inclusions. However, the exact nature, composition, temporal evolution, and underlying mechanisms of yeast alpha-syn accumulations and their relevance to human synucleinopathies are unknown. Here we provide ultrastructural evidence that alpha-syn accumulations are not comprised of LB-like fibrils, but are associated with clusters of vesicles. Live-cell imaging showed alpha-syn initially localized to the plasma membrane and subsequently formed accumulations in association with vesicles. Imaging of truncated and mutant forms of alpha-syn revealed the molecular determinants and vesicular trafficking pathways underlying this pathological process. Because vesicular clustering is also found in LB-containing neurons of PD brains, alpha-syn-mediated vesicular accumulation in yeast represents a model system to study specific aspects of neurodegeneration in PD and related synucleinopathies.

Integrin-linked kinase (ILK) plays key roles in a variety of cell functions, including cell proliferation, adhesion and migration. Within the cell, ILK localizes to multiple sites, including the cytoplasm, focal adhesion complexes that mediate cell adhesion to extracellular substrates, as well as cell-cell junctions in epidermal keratinocytes. Central to understanding ILK function is the elucidation of the mechanisms that regulate its subcellular localization. We now demonstrate that ILK is imported into the nucleus through sequences in its N-terminus, via active transport mechanisms that involve nuclear pore complexes. In addition, nuclear ILK can be rapidly exported into the cytoplasm through a CRM1-dependent pathway, and its export is enhanced by the type 2C protein phosphatase ILKAP. Nuclear localization of ILK in epidermal keratinocytes is associated with increased DNA synthesis, which is sensitive to inhibition by ILKAP. Our studies demonstrate the importance for keratinocyte proliferation of ILK regulation through changes in its subcellular localization, and establish ILKAP and CRM1 as pivotal modulators of ILK subcellular distribution and activity in these cells.

Cells of the unicellular eukaryote Dictyostelium discoideum take up all their nutrients by endocytosis. Both particle- and fluid-containing vacuoles are transiently surrounded by a cytoskeletal coat [1] [2]. When this coat has dissociated, acidification and digestion of the vesicle contents occur, followed by exocytosis of the indigestible remnants after 60-90 minutes. At least nine compartments are needed for mathematical modelling of endocytic transit [3], suggesting that markers associate for only a few minutes with a specific endocytic compartment. Among the proteins that have been identified as components of endocytic vesicles are actin, subunits of the V-H+ ATPase and small GTP-binding proteins of the Rab family [4] [5] [6] [7]. Using a monoclonal antibody produced against Dictyostelium endocytic vesicles, we have isolated a cDNA corresponding to a novel protein that we have named vacuolin. In order to determine the precise step along the endocytic pathway that involves vacuolin, we generated a fusion protein of the green fluorescent protein (GFP) and vacuolin. GFP-vacuolin-decorated vesicles were identified as a post-lysosomal compartment that acquires endocytic markers shortly before exocytosis. At earlier stages, this post-lysosomal compartment was identified by the binding of a tagged cytoskeletal protein, coronin-GFP. Vacuoles were coated with filamentous actin along the entire post-lysosomal pathway, and the integrity of the actin coat was required for exocytosis.