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The Pseudophosphatase MK-STYX Colocalizes to Aggresomes
Nagle, Veronica L.
Nagle, Veronica L.
Abstract
MK-STYX [MAPK (mitogen-activated protein kinase) phosphoserine/threonine/tyrosine-binding protein] is a pseudophosphatase member of the dual-specificity family subfamily of protein tyrosine phosphatases. MK-STYX lacks the essential cysteine in its signature motif required for catalytic activity. However, mutations to “restore” the signature motif result in a catalytically active phosphatase, MK-STYXactive (F1). We reported that MK-STYX interacts with G3BP-1 [Ras-GAP (GTPAse-activating protein) SH3 (Src homology 3) domain binding protein-1], and inhibits stress granule (SG) formation implicating the pseudophosphatase MK-STYX in the stress response pathway. SGs are large structures in which untranslated mRNAs accumulate and may serve as sites of mRNA sorting, when cells are under stress. Prolonged stress granules are associated with aggresome (misfolded proteins) formation; cytotoxic aggresomes may result in neurological disorders such as amyotrophic lateral sclerosis or Alzheimer’s. Fluorescence microscopy data demonstrate that MK-STYX colocalizes with specific aggresomes. Coexpression experiments in HeLa cells with MK-STYX and the aggresome marker v-ErbA show that MK-STYX colocalizes to v-ErbA aggresomes as well as with the aggresome marker protein chimera (GFP-250). These data reveal that MK-STYX localizes to aggresomes. Taken together with our prior report that MK-STYX inhibits SGs, this work may illustrate a role for MK-STYX in the response to environmental stress through regulation of protein synthesis.
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2016-05-01
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Biology