Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0004134 (ataxia)
 15,886 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Nicotinamide mononucleotide adenylyltransferase (NMNAT) is a conserved enzyme in the NAD synthetic pathway. It has also been identified as an effective and versatile neuroprotective factor. However, it remains unclear how healthy neurons regulate the dual functions of NMNAT and achieve self-protection under stress. Here we show that Drosophila Nmnat (DmNmnat) is alternatively spliced into two mRNA variants, RA and RB, which translate to protein isoforms with divergent neuroprotective capacities against spinocerebellar ataxia 1-induced neurodegeneration. Isoform PA/PC translated from RA is nuclear-localized with minimal neuroprotective ability, and isoform PB/PD translated from RB is cytoplasmic and has robust neuroprotective capacity. Under stress, RB is preferably spliced in neurons to produce the neuroprotective PB/PD isoforms. Our results indicate that alternative splicing functions as a switch that regulates the expression of functionally distinct DmNmnat variants. Neurons respond to stress by driving the splicing switch to produce the neuroprotective variant and therefore achieve self-protection.
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PMID:Alternative splicing of Drosophila Nmnat functions as a switch to enhance neuroprotection under stress. 2661 31

The plasma membrane Ca2+ ATPases (PMCAs) are responsible for the clearance of Ca2+ out of cells after intracellular Ca2+ transients. Cooperating with Na+/Ca2+ exchangers (NCXs) and Ca2+ buffering proteins, PMCAs play an essential role in maintaining the long-term cellular Ca2+ homeostasis. The plasma membrane Ca2+ ATPase was first discovered in red blood cell membrane about 50 years ago, and then other PMCA isoforms and alternatively spliced variants had been identified from different tissues and different developmental stages, revealing a surprising complexity of the PMCA family. In mammals, there are four PMCA isoforms encoded by four distinct genes. Isoform 1 and 4 are found in virtually all tissues, whereas isoform 2 and 3 are primarily expressed in excitable cells such as neurons and myocytes. Perturbation of PMCAs function has been implicated in a variety of diseases and disorders, including hearing loss, ataxia, paraplegia, and infertility. Here, we would like to review the recent progresses in the study of the PMCAs and related disorders, in particular how these pathological conditions help us to gain an in-depth insight into the function of PMCAs and their contribution in the regulation of Ca2+ signaling network.
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PMID:The Plasma Membrane Calcium ATPases in Calcium Signaling Network. 2966 80

The most commonly inherited dominant ataxia, Spinocerebellar Ataxia Type 3 (SCA3), is caused by a CAG repeat expansion that encodes an abnormally long polyglutamine (polyQ) repeat in the disease protein ataxin-3, a deubiquitinase. Two major full-length isoforms of ataxin-3 exist, both of which contain the same N-terminal portion and polyQ repeat, but differ in their C-termini; one (denoted here as isoform 1) contains a motif that binds ataxin-3's substrate, ubiquitin, whereas the other (denoted here as isoform 2) has a hydrophobic tail. Most SCA3 studies have focused on isoform 1, the predominant version in mammalian brain, yet both isoforms are present in brain and a better understanding of their relative pathogenicity in vivo is needed. We took advantage of the fruit fly, Drosophila melanogaster to model SCA3 and to examine the toxicity of each ataxin-3 isoform. Our assays reveal isoform 1 to be markedly more toxic than isoform 2 in all fly tissues. Reduced toxicity from isoform 2 is due to much lower protein levels as a result of its expedited degradation. Additional studies indicate that isoform 1 is more aggregation-prone than isoform 2 and that the C-terminus of isoform 2 is critical for its enhanced proteasomal degradation. According to our results, although both full-length, pathogenic ataxin-3 isoforms are toxic, isoform 1 is likely the primary contributor to SCA3 due to its presence at higher levels. Isoform 2, as a result of rapid degradation that is dictated by its tail, is unlikely to be a key player in this disease. Our findings provide new insight into the biology of this ataxia and the cellular processing of the underlying disease protein.
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PMID:Differential toxicity of ataxin-3 isoforms in Drosophila models of Spinocerebellar Ataxia Type 3. 3131 Aug 2