α-Synuclein is a presynaptic neuronal protein that is linked genetically and neuropathologically to Parkinson's disease (PD). α-Synuclein may contribute to PD pathogenesis in a number of ways, but it is generally thought that its aberrant soluble oligomeric conformations, termed protofibrils, are the toxic species that mediate disruption of cellular homeostasis and neuronal death, through effects on various intracellular targets, including synaptic function. Furthermore, secreted α-synuclein may exert deleterious effects on neighboring cells, including seeding of aggregation, thus possibly contributing to disease propagation. Although the extent to which α-synuclein is involved in all cases of PD is not clear, targeting the toxic functions conferred by this protein when it is dysregulated may lead to novel therapeutic strategies not only in PD, but also in other neurodegenerative conditions, termed synucleinopathies.

/pdf/a-synuclein-in-parkinson-s-disease-jswzbre492.pdf

α-Synuclein in Parkinson’s Disease

The ANL superfamily of adenylating enzymes contains acyl- and aryl-CoA synthetases, firefly luciferase, and the adenylation domains of the modular non-ribosomal peptide synthetases (NRPSs). Members of this family catalyze two partial reactions: the initial adenylation of a carboxylate to form an acyl-AMP intermediate, followed by a second partial reaction, most commonly the formation of a thioester. Recent biochemical and structural evidence has been presented that supports the use by this enzyme family of a remarkable catalytic strategy for the two catalytic steps. The enzymes use a 140 degrees domain rotation to present opposing faces of the dynamic C-terminal domain to the active site for the different partial reactions. Support for this domain alternation strategy is presented along with an explanation of the advantage of this catalytic strategy for the reaction catalyzed by the ANL enzymes. Finally, the ramifications of this domain rotation in the catalytic cycle of the modular NRPS enzymes are discussed.

Conformational dynamics in the Acyl-CoA synthetases, adenylation domains of non-ribosomal peptide synthetases, and firefly luciferase.

Several neurodegenerative diseases are typified by intraneuronal α-synuclein deposits, synaptic dysfunction, and dementia. While even modest α-synuclein elevations can be pathologic, the precise cascade of events induced by excessive α-synuclein and eventually culminating in synaptotoxicity is unclear. To elucidate this, we developed a quantitative model system to evaluate evolving α-synuclein-induced pathologic events with high spatial and temporal resolution, using cultured neurons from brains of transgenic mice overexpressing fluorescent-human-α-synuclein. Transgenic α-synuclein was pathologically altered over time and overexpressing neurons showed striking neurotransmitter release deficits and enlarged synaptic vesicles; a phenotype reminiscent of previous animal models lacking critical presynaptic proteins. Indeed, several endogenous presynaptic proteins involved in exocytosis and endocytosis were undetectable in a subset of transgenic boutons (“vacant synapses”) with diminished levels in the remainder, suggesting that such diminutions were triggering the overall synaptic pathology. Similar synaptic protein alterations were also retrospectively seen in human pathologic brains, highlighting potential relevance to human disease. Collectively the data suggest a previously unknown cascade of events where pathologic α-synuclein leads to a loss of a number of critical presynaptic proteins, thereby inducing functional synaptic deficits.

https://www.jneurosci.org/content/jneuro/30/24/8083.full.pdf

A Pathologic Cascade Leading to Synaptic Dysfunction in α-Synuclein-Induced Neurodegeneration

a-Synuclein is a presynaptic neuronal protein that is linked genetically and neuropathologically to Parkinson’s disease (PD). a-Synuclein may contribute to PD pathogenesis in a number of ways, but it is generally thought that its aberrant soluble oligomeric conformations, termed protofibrils, are the toxic species that mediate disruption of cellular homeostasis and neuronal death, through effects on various intracellular targets, including synaptic function. Furthermore, secreted a-synuclein may exert deleterious effects on neighboring cells, including seeding of aggregation, thus possibly contributing to disease propagation. Although the extent to whicha-synuclein is involved in all cases of PD is not clear, targeting the toxic functions conferred by this protein when it is dysregulated may lead to novel therapeutic strategies not only in PD, but also in other neurodegenerative conditions, termed synucleinopathies.

a-Synuclein in Parkinson's Disease

α-synuclein Induces Mitochondrial Dysfunction through Spectrin and the Actin Cytoskeleton.

The recent discovery of fatty acyl-AMP ligases (FAALs) in Mycobacterium tuberculosis (Mtb) provided a new perspective to fatty acid activation dogma. These proteins convert fatty acids to corresponding adenylates, which is an intermediate of acyl-CoA-synthesizing fatty acyl-CoA ligases (FACLs). Presently, it is not evident how obligate pathogens like Mtb have evolved such new themes of functional versatility and whether the activation of fatty acids to acyl-adenylates could indeed be a general mechanism. Here, based on elucidation of the first structure of a FAAL protein and by generating loss- as well as gain-of-function mutants that interconvert FAAL and FACL activities, we demonstrate that an insertion motif dictates formation of acyl-adenylate. Since FAALs in Mtb are crucial nodes in biosynthetic network of virulent lipids, inhibitors directed against these proteins provide a unique multi-pronged approach of simultaneously disrupting several pathways.

/pdf/mechanistic-and-functional-insights-into-fatty-acid-1cpsste3mz.pdf

Mechanistic and functional insights into fatty acid activation in Mycobacterium tuberculosis

The function of α-synuclein, a soluble protein abundant in the brain and concentrated at presynaptic terminals, is still undefined. Yet, α-synuclein overexpression and the expression of its A30P mu...

/pdf/a-synuclein-and-its-a30p-mutant-affect-actin-cytoskeletal-4a6gn0by4l.pdf

α-Synuclein and Its A30P Mutant Affect Actin Cytoskeletal Structure and Dynamics

FadD28 from Mycobacterium tuberculosis belongs to the fatty-acyl AMP ligase (FAAL) family of proteins. It is essential for the biosynthesis of a virulent phthiocerol dimycocerosate (PDIM) lipid that is only found in the cell wall of pathogenic mycobacteria. The N-terminal domain, comprising of the first 460 residues, was crystallized by the hanging-drop vapour-diffusion method at 295 K. The crystals belong to space group P212121, with unit-cell parameters a = 50.97, b = 60.74, c = 136.54 A. The crystal structure of the N-terminal domain of FadD28 at 2.35 A resolution has been solved using the MAD method.

/pdf/crystallization-and-preliminary-x-ray-crystallographic-5auu58s9iz.pdf

Crystallization and preliminary X-ray crystallographic studies of the N-terminal domain of FadD28, a fatty-acyl AMP ligase from Mycobacterium tuberculosis.

Malikmohamed Yousuf

Papers

Mechanistic and functional insights into fatty acid activation in Mycobacterium tuberculosis

α-Synuclein and Its A30P Mutant Affect Actin Cytoskeletal Structure and Dynamics

Crystallization and preliminary X-ray crystallographic studies of the N-terminal domain of FadD28, a fatty-acyl AMP ligase from Mycobacterium tuberculosis.