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Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder characterized by progressive motor neuron death.More than 90 mutations in the copper-zinc superoxide dismutase (SOD1) gene cause a subset of familial ALS. Toxic properties have been proposed for the ALS-linked SOD1 mutants, but the nature of the toxicity has not been clearly specified. Cytoplasmic inclusion bodies containing mutant SOD1 and a number of other proteins are a pathological hallmark of mutant SOD1-mediated familial ALS, but whether such aggregates are toxic to motor neurons remains unclear. In this study, we identified a dynein subunit as a component of the mutant SOD1-containing high molecular weight complexes using proteomic techniques. We further demonstrated interaction and colocalization between dynein and mutant SOD1, but not normal SOD1, in cultured cells and also in G93A and G85R transgenic rodent tissues. Moreover, the interaction occurred early, prior to the onset of symptoms in the ALS animal models and increased over the disease progression. Motor neurons with long axons are particularly susceptible to defects in axonal transport. Our results demonstrate a direct "gain-of-interaction" between mutant SOD1 and dynein, which may provide insights into the mechanism by which mutant SOD1 could contribute to a defect in retrograde axonal transport or other dynein functions. The aberrant interaction is potentially critical to the formation of mutant SOD1 aggregates as well as the toxic cascades leading to motor neuron degeneration in ALS.

The difficulty in accessing mammalian nephrons in vivo hinders the study of podocyte biology. The Drosophila nephrocyte shares remarkable similarities to the glomerular podocyte, but the lack of a functional readout for nephrocytes makes it challenging to study this model of the podocyte, which could potentially harness the power of Drosophila genetics. Here, we present a functional analysis of nephrocytes and establish an in vivo system to screen for renal genes. We found that nephrocytes efficiently take up secreted fluorescent protein, and therefore, we generated a transgenic line carrying secreted fluorescent protein and combined it with a nephrocyte-specific driver for targeted gene knockdown, allowing the identification of genes required for nephrocyte function. To validate this system, we examined the effects of knocking down sns and duf, the Drosophila homologs of nephrin and Neph1, respectively, in pericardial nephrocytes. Knockdown of sns or duf completely abolished the accumulation of the fluorescent protein in pericardial nephrocytes. Examining the ultrastructure revealed that the formation of the nephrocyte diaphragm and lacunar structure, which is essential for protein uptake, requires sns. Our preliminary genetic screen also identified Mec2, which encodes the homolog of mammalian Podocin. Taken together, these data suggest that the Drosophila pericardial nephrocyte is a useful in vivo model to help identify genes involved in podocyte biology and facilitate the discovery of renal disease genes.

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by motor neuron death. A hallmark of the disease is the appearance of protein aggregates in the affected motor neurons. We have found that p62, a protein implicated in protein aggregate formation, accumulated progressively in the G93A mouse spinal cord. The accumulation of p62 was in parallel to the increase of polyubiquitinated proteins and mutant SOD1 aggregates. Immunostaining studies showed that p62, ubiquitin, and mutant SOD1 co-localized in the protein aggregates in affected cells in G93A mouse spinal cord. The p62 protein selectively interacted with familial ALS mutants, but not WT SOD1. When p62 was co-expressed with SOD1 in NSC34 cells, it greatly enhanced the formation of aggregates of the ALS-linked SOD1 mutants, but not wild-type SOD1. Cell viability was measured in the presence and absence of overexpressed p62, and the results suggest that the large aggregates facilitated by p62 were not directly toxic to cells under the conditions in this study. Deletion of the ubiquitin-association (UBA) domain of p62 significantly decreased the p62-facilitated aggregate formation, but did not completely inhibit it. Further protein interaction experiments also showed that the truncated p62 with the UBA domain deletion remained capable of interacting with mutant SOD1. The findings of this study show that p62 plays a critical role in forming protein aggregates in familial ALS, likely by linking misfolded mutant SOD1 molecules and other cellular proteins together. Amyotrophic lateral sclerosis (ALS)3 is a progressive neurodegenerative disorder leading to the selective death of motor neurons (1, 2). The majority of cases are sporadic, but about 10% of all cases are familial (fALS). In ϳ20% of familial cases, a mutant allele of the copper-zinc superoxide dismutase (SOD1) enzyme has been identified (3-5). As of today, over 100 different mutations of SOD1 causing ALS have been reported, the majority of which are point mutations and act in a dominant fashion. Several ALS risk factors have been identified, but the etiology of the disease is largely unclear. A hallmark of the disease is the appearance of intracellular inclusions in degenerating motor neurons (6), both in the familial cases caused by mutations in SOD1 and in the more obscure sporadic cases (6 -11). The formation of such protein aggregates precedes neuronal death (12). The inclusions are typically SOD1 and ubiquitin immunoreactive in the mutant SOD1-mediated fALS cases (2, 7-9, 11-13). However, it is unclear how the SOD1 mutants form aggregates and whether other proteins play any role in the aggregation process or the aggregate-induced toxicity.p62 (also called sequestosome 1) was first identified as a phosphotyrosine-independent ligand for the Lck SH2 domain (14). It was later found to be a polyubiquitin-binding protein (15)(16)(17). The expression of p62 is up-regulated by several stress conditions, e.g. oxidative stress (18,19), proteasome inhibition (19 -21), or p...

The insect nephrocyte and the mammalian glomerular podocyte are similar with regard to filtration, but it remains unclear whether there is an organ or cell type in flies that reabsorbs proteins. Here, we show that the Drosophila nephrocyte has molecular, structural, and functional similarities to the renal proximal tubule cell. We screened for genes required for nephrocyte function and identified two Drosophila genes encoding orthologs of mammalian cubilin and amnionless (AMN), two major receptors for protein reabsorption in the proximal tubule. In Drosophila, expression of dCubilin and dAMN is specific to nephrocytes, where they function as co-receptors for protein uptake. Targeted expression of human AMN in Drosophila nephrocytes was sufficient to rescue defective protein uptake induced by dAMN knockdown, suggesting evolutionary conservation of Cubilin/AMN co-receptors function from flies to humans. Furthermore, we found that Cubilin/ AMN-mediated protein reabsorption is required for the maintenance of nephrocyte ultrastructure and fly survival under conditions of toxic stress. In conclusion, the insect nephrocyte combines filtration with protein reabsorption, using evolutionarily conserved genes and subcellular structures, suggesting that it can serve as a simplified model for both podocytes and the renal proximal tubule.

Mutations in copper-zinc superoxide dismutase (SOD1) have been linked to a subset of familial amytrophic lateral sclerosis (fALS), a fatal neurodegenerative disease characterized by progressive motor neuron death. An increasing amount of evidence supports that mitochondrial dysfunction and apoptosis activation play a critical role in the fALS etiology, but little is known about the mechanisms by which SOD1 mutants cause the mitochondrial dysfunction and apoptosis. In this study, we use proteomic approaches to identify the mitochondrial proteins that are altered in the presence of a fALS-causing mutant G93A-SOD1. A comprehensive characterization of mitochondrial proteins from NSC34 cells, a motor neuron-like cell line, was achieved by two independent proteomic approaches. Four hundred seventy unique proteins were identified in the mitochondrial fraction collectively, 75 of which are newly discovered proteins that previously had only been reported at the cDNA level. Two-dimensional gel electrophoresis was subsequently used to analyze the differences between the mitochondrial proteomes of NSC34 cells expressing wild-type and G93A-SOD1. Nine and 36 protein spots displayed elevated and suppressed abundance respectively in G93A-SOD1-expressing cells. The 45 spots were identified by MS, and they include proteins involved in mitochondrial membrane transport, apoptosis, the respiratory chain, and molecular chaperones. In particular, alterations in the post-translational modifications of voltage-dependent anion channel 2 (VDAC2) were found, and its relevance to regulating mitochondrial membrane permeability and activation of apoptotic pathways is discussed. The potential role of other proteins in the mutant SOD1-mediated fALS is also discussed. This study has produced a short list of mitochondrial proteins that may hold the key to the mechanisms by which SOD1 mutants cause mitochondrial dysfunction and neuronal death. Amyotrophic lateral sclerosis (ALS)1 is a fatal neurodegenerative disease characterized by progressive motor neuron death. Approximately 10% of ALS patients are familial cases (fALS), and mutations in the gene encoding copper-zinc superoxide dismutase (SOD1) were linked with a subset of fALS (1, 2). To date, more than 90 mutations in SOD1 are known to be responsible for ϳ25% of fALS (3), most of which are point mutations that are scattered throughout the primary sequence and structure of the protein. There has been intensive research focusing on the etiology of SOD1 mutant-mediated fALS (see reviews in . It has been demonstrated that SOD1-null mice did not develop the disease (9). In addition, transgenic mice expressing the ALS-associated mutants G93A-SOD1 (10, 11), G37R-SOD1 (12), and G85R-SOD1 (13, 14) as well as transgenic rats expressing G93A-SOD1 (15, 16) and H46R-SOD1 (16) developed progressive motor neuron disease despite normal or elevated SOD1 activity. Therefore, it is believed that the ALS-linked mutants of SOD1 have acquired unknown toxic properties that eventually lead to the disease. However, ...

Summary This paper proposes an identification framework based on a restricted Boltzmann machine (RBM) for crack identification and extraction from images containing cracks and complicated background inside steel box girders of bridges. The original images that include fatigue crack and other background information are obtained by a consumer‐grade camera inside the steel box girder. The original images are cut into a number of elements with small size as the input dataset, and a state representation vector is artificially labeled to every image element used for the crack identification. A deep learning model or network consisting of multiple processing RBM layers to learn the abstract features is constructed to match the input image elements with corresponding state representation vectors. Next, a three‐layer RBM with 500; 500; and 2,000 hidden units is trained as the hidden layers in the deep learning network. A contrastive divergence learning algorithm is employed for training the deep network to update and obtain the optimal parameters (i.e., the biases and weights). The new input image elements labeled as crack are sorted out and assembled to form an output image. A deep network is modeled through the consumer‐grade camera images containing cracks and complicated background information using the proposed approach. The accuracy and ability to identify cracks from new images with different resolutions using the trained deep network are validated. Furthermore, effects of element size on reconstruction error and identification accuracy are investigated. The results show that there exists optimal element size; that is, too small and too large element sizes both increase the reconstruction error and decrease the identification accuracy.

SUMMARYStay cables are critical components in bridges. However, stay cables suffer from severe fatigue damage. Therefore, a monitoring technique to obtain the time history of the tension in stay cables is important. Because the acceleration of stay cables is readily measurable, approaches to identify cable tension based on frequency analysis and monitored cable acceleration have been widely investigated and used in practice. However, this type of approach can only identify a time‐invariant tension of a stay cable over a specified duration, not the time‐varying tension. This paper proposes an approach to identify the time‐varying tension of stay cables by monitoring cable accelerations. The tension variation in stay cables is caused by vehicles passing over the bridge. The real‐time identification algorithm that determines the time‐varying tension of stay cables is proposed using an extended Kalman filter based on both the transversal monitored acceleration at a single location on the cable and the monitored wind speed on the bridge, where the time‐varying tension is a state variable that is identified. A stay cable from the Nanjing Yangtze River No. 3 Bridge was used for the numerical study. The time‐varying tension of the stay cable can be identified when either a single vehicle or multiple vehicles pass over the bridge. The robustness of the proposed approach is also investigated through deviations in the initial tension, initial displacement, and velocity of the stay cable. An experiment was conducted on a scaled stay cable with time‐varying tension excited by wind. The time‐varying cable tension of the cable was identified by the proposed approach and compared with the real time‐varying cable tension. The identification accuracy and robustness of the proposed approach is verified through the experiment and numerical study. Copyright © 2013 John Wiley & Sons, Ltd.