TIA-1 is an RNA binding protein that promotes the assembly of stress granules (SGs), discrete cytoplasmic inclusions into which stalled translation initiation complexes are dynamically recruited in cells subjected to environmental stress. The RNA recognition motifs of TIA-1 are linked to a glutamine-rich prion-related domain (PRD). Truncation mutants lacking the PRD domain do not induce spontaneous SGs and are not recruited to arsenite-induced SGs, whereas the PRD forms aggregates that are recruited to SGs in low-level-expressing cells but prevent SG assembly in high-level-expressing cells. The PRD of TIA-1 exhibits many characteristics of prions: concentration-dependent aggregation that is inhibited by the molecular chaperone heat shock protein (HSP)70; resistance to protease digestion; sequestration of HSP27, HSP40, and HSP70; and induction of HSP70, a feedback regulator of PRD disaggregation. Substitution of the PRD with the aggregation domain of a yeast prion, SUP35-NM, reconstitutes SG assembly, confirming that a prion domain can mediate the assembly of SGs. Mouse embryomic fibroblasts (MEFs) lacking TIA-1 exhibit impaired ability to form SGs, although they exhibit normal phosphorylation of eukaryotic initiation factor (eIF)2alpha in response to arsenite. Our results reveal that prion-like aggregation of TIA-1 regulates SG formation downstream of eIF2alpha phosphorylation in response to stress.

TIA-1 and TTP are AU-rich element-binding proteins that prevent the pathological overexpression of tumor necrosis factor ␣ (TNF-␣). TIA-1 inhibits the translation of TNF-␣ transcripts, whereas TTP promotes the degradation of TNF-␣ transcripts. Here we show that TIA-1 and TTP function as arthritis suppressor genes: TIA-1 ؊/؊ mice develop mild arthritis, TTP ؊/؊ mice develop severe arthritis, and TIA-1 ؊/؊ TTP ؊/؊ mice develop very severe arthritis. Peritoneal macrophages derived from all three genotypes overexpress cyclooxygenase 2 and TNF-␣. Surprisingly, lipopolysaccharide-activated TIA-1 ؊/؊ TTP ؊/؊ macrophages secrete less TNF-␣ protein than either TIA-1 ؊/؊ or TTP ؊/؊ macrophages. In these mice, arthritogenic cytokine may be produced by neutrophils that accumulate in the bone marrow and peripheral blood. Our results suggest that TIA-1 and TTP are genetic modifiers of inflammatory arthritis that can alter the spectrum of cells that produce arthritogenic cytokines.protein translation ͉ mRNA stability ͉ coordinate expression

Succinic semialdehyde dehydrogenase (SSADH) deficiency is an heritable disorder of GABA degradation characterized by ataxia, psychomotor retardation and seizures. To date, there is no effective treatment for SSADH deficiency. We tested the hypothesis that a ketogenic diet (KD) would improve outcome in an animal model of SSADH deficiency, the SSADH knockout mouse (Aldh5a1 −/− ). Using a 4:1 ratio of fat to combined carbohydrate and protein KD we set out to compare the general phenotype, in vivo and in vitro electrophysiology and [ 35 S]TBPS binding in both Aldh5a1 −/− mice and control (Aldh5a1 +/+ ) mice. We found that the KD prolonged the lifespan of mutant mice by >300% with normalization of ataxia, weight gain and EEG compared to mutants fed a control diet. Aldh5a1 −/− mice showed significantly reduced mIPSC frequency in CA1 hippocampal neurons as well as significantly decreased [ 35 S]TBPS binding in all brain areas examined. In KD fed mutants, mIPSC activity normalized and [ 35 S]TBPS binding was restored in the cortex and hippocampus. The KD appears to reverse toward normal the perturbations seen in Aldh5a1 −/− mice. Our data suggest that the KD may work in this model by restoring GABAergic inhibition. These data demonstrate a successful experimental treatment for murine SSADH deficiency using a KD, giving promise to the idea that the KD may be successful in the clinical treatment of SSADH deficiency.

The GABAB R-coupled GIRK2 channel is necessary for the GABAB R agonist-induced infantile spasms phenotype in the Ts mouse and may represent a novel therapeutic target for the treatment of infantile spasms in DS. Ann Neurol 2016;80:511-521.