T-cell-restricted Intracellular Antigen-1 Research Articles

Molecular and clinicopathological features of granzyme B-negative extranodal NK/T-cell lymphoma

Extranodal NK/T-cell lymphoma (ENKTL) generally expresses cytotoxic molecules, including granzyme B (GZMB), T-cell-restricted intracellular antigen-1 (TIA-1), and perforin; however, the expression of these molecules varies across cases. We performed gene expression profiling and identified unique biological and clinicopathological features of GZMB-negative ENKTL. We reviewed the clinicopathological characteristics of 71 ENKTL samples. Gene expression profiling on nine ENKTLs using multiplexed, direct, and digital mRNA quantification divided ENKTLs into Groups A (n = 7) and B (n = 2) through hierarchical clustering and t-distributed stochastic neighbor embedding. Group B was characterized by downregulation of genes associated with IL6-JAK-STAT3 signaling and inflammatory responses. GZMB mRNA expression was significantly downregulated in Group B. GZMB protein expression was evaluated with immunohistochemistry in all 71 ENKTLs, and expression data of Tyr705-phosphorylated STAT3 (pSTAT3) and MYC from our previous study was utilized. T-cell receptor gamma (TRG) gene rearrangement in the selected samples was also assessed using PCR. GZMB expression was higher in pSTAT3-positive (p = 0.028) and MYC-positive (p = 0.014) ENKTLs. Eighteen percent (13/71) of all ENKTLs were negative for GZMB (defined by positivity <10 %); patients with GZMB-negative ENKTLs were often in a higher clinical stage (p = 0.016). We observed no other correlations with clinical parameters or TRG rearrangement and no significant association between GZMB expression and survival. In conclusion, GZMB expression is highly heterogeneous in ENKTLs and is associated with the activation of the JAK-STAT3 pathway and higher MYC expression. GZMB-negative ENKTLs correlate with an advanced clinical stage, suggesting the potential utility of GZMB immunohistochemistry as a biomarker of ENKTL.

A novel stroke rehabilitation strategy and underlying stress granule regulations through inhibition of NLRP3 inflammasome activation.

Dynamic changes in ischemic pathology after stroke suggested a "critical window" of enhanced neuroplasticity immediately after stroke onset. Although physical exercise has long been considered a promising strategy of stroke rehabilitation, very early physical exercise may exacerbate brain injury. Since remote ischemic conditioning (RIC) promotes neuroprotection and neuroplasticity, the present study combined RIC with sequential exercise to establish a new rehabilitation strategy for a better rehabilitative outcome. A total of 120 adult male Sprague-Dawley rats were used and divided into five groups: (1) sham, (2) stroke, (3) stroke with exercise, (4) stroke with RIC, and (5) stroke with RIC followed by exercise. Brain damage was evaluated by infarct volume, neurological deficit, cell death, and lactate dehydrogenase (LDH) activity. Long-term functional outcomes were determined by grid walk tests, rotarod tests, beam balance tests, forelimb placing tests, and the Morris water maze. Neuroplasticity was evaluated through measurements of both mRNA and protein levels of synaptogenesis (synaptophysin [SYN], post-synaptic density protein-95 [PSD-95], and brain-derived neurotrophic factor [BDNF]) and angiogenesis (vascular endothelial growth factor [VEGF], angiopoietin-1 [Ang-1], and angiopoietin-2 [Ang-2]). Inflammasome activation was measured by concentrations of interleukin-18 (IL-18) and IL-1β detected by enzyme-linked immunosorbent assay (ELISA) kits, mRNA expressions of NLR pyrin domain containing 3 (NLRP3), apoptosis-associated speck-like protein containing a C-terminal caspase recruitment domain (ASC), IL-18 and IL-1β, and protein quantities of NLRP3, ASC, cleaved-caspase-1, gasdermin D-N (GSDMD-N), and IL-18 and IL-1β. Stress granules (SGs), including GTPase-activating protein-binding protein 1 (G3BP1), T cell-restricted intracellular antigen-1 (TIA1), and DEAD-box RNA helicase 3X (DDX3X) were evaluated at mRNA and protein levels. The interactions between DDX3X with NLRP3 or G3BP1 were determined by immunofluorescence and co-immunoprecipitation. Early RIC decreased infarct volumes, neurological deficits, cell death, and LDH activity at post-stroke Day 3 (p < 0.05). All treatment groups showed significant improvement in functional outcomes, including sensory, motor, and cognitive functions. RIC and exercise, as compared to RIC or physical exercise alone, had improved functional outcomes after stroke (p < 0.05), as well as synaptogenesis and angiogenesis (p < 0.05). RIC significantly reduced mRNA and protein expressions of NLRP3 (p < 0.05). SGs formation peaked at 0 h after ischemia, then progressively decreased until 24 h postreperfusion, which was reversed by RIC (p < 0.05). The assembly of SGs consumed DDX3X and then inhibited NLRP3 inflammasome activation. RIC followed by exercise induced a better rehabilitation in ischemic rats, while early RIC alleviated ischemia-reperfusion injury via stress-granule-mediated inhibition of NLRP3 inflammasome.

Stress granule activation attenuates lipopolysaccharide-induced cardiomyocyte dysfunction

BackgroundSepsis is the leading cause of death in intensive care units. Sepsis-induced myocardial dysfunction, one of the most serious complications of sepsis, is associated with higher mortality rates. As the pathogenesis of sepsis-induced cardiomyopathy has not been fully elucidated, there is no specific therapeutic approach. Stress granules (SG) are cytoplasmic membrane-less compartments that form in response to cellular stress and play important roles in various cell signaling pathways. The role of SG in sepsis-induced myocardial dysfunction has not been determined. Therefore, this study aimed to determine the effects of SG activation in septic cardiomyocytes (CMs).MethodsNeonatal CMs were treated with lipopolysaccharide (LPS). SG activation was visualized by immunofluorescence staining to detect the co-localization of GTPase-activating protein SH3 domain binding protein 1 (G3BP1) and T cell-restricted intracellular antigen 1 (TIA-1). Eukaryotic translation initiation factor alpha (eIF2α) phosphorylation, an indicator of SG formation, was assessed by western blotting. Tumor necrosis factor alpha (TNF-α) production was assessed by PCR and enzyme-linked immunosorbent assays. CMs function was evaluated by intracellular cyclic adenosine monophosphate (cAMP) levels in response to dobutamine. Pharmacological inhibition (ISRIB), a G3BP1 CRISPR activation plasmid, and a G3BP1 KO plasmid were employed to modulate SG activation. The fluorescence intensity of JC-1 was used to evaluate mitochondrial membrane potential.ResultsLPS challenge in CMs induced SG activation and resulted in eIF2α phosphorylation, increased TNF-α production, and decreased intracellular cAMP in response to dobutamine. The pharmacological inhibition of SG (ISRIB) increased TNF-α expression and decreased intracellular cAMP levels in CMs treated with LPS. The overexpression of G3BP1 increased SG activation, attenuated the LPS-induced increase in TNF-α expression, and improved CMs contractility (as evidenced by increased intracellular cAMP). Furthermore, SG prevented LPS-induced mitochondrial membrane potential dissipation in CMs.ConclusionSG formation plays a protective role in CMs function in sepsis and is a candidate therapeutic target.

TIA1 Loss Exacerbates Fatty Liver Disease but Exerts a Dual Role in Hepatocarcinogenesis

Simple SummaryHepatocellular carcinoma (HCC) is a leading cause of cancer mortality worldwide with few and poorly efficient therapeutic options. Adenylate–uridylate-rich-element-binding proteins (AUBPs) are potent post-transcriptional regulators of gene expression, whose alterations have been associated with the development of chronic liver diseases (e.g., fatty liver disease) and their progression toward HCC. Emerging evidence indicates that T-Cell-restricted intracellular antigen-1 (TIA1), an AUBP regulating mRNA translation, promotes HCC. Herein, we further characterize TIA1’s functions in hepatic cancer cells by identifying an entire set of oncogenes and tumor suppressors under TIA1’s influence, thus suggesting a dual role in hepatocarcinogenesis. In agreement, using in vivo models, we found that contrary to our observations in HCC cells, TIA1 can exert a tumor suppressive function and refrain from hepatic steatosis and fibrosis. Finally, TIA1 expression is reduced in human HCC. Our study provides new insights regarding the role for TIA1 in HCC and questions the current concept of TIA1 as a strict tumor promoter.Alterations in specific RNA-binding protein expression/activity importantly contribute to the development of fatty liver disease (FLD) and hepatocellular carcinoma (HCC). In particular, adenylate–uridylate-rich element binding proteins (AUBPs) were reported to control the post-transcriptional regulation of genes involved in both metabolic and cancerous processes. Herein, we investigated the pathophysiological functions of the AUBP, T-cell-restricted intracellular antigen-1 (TIA1) in the development of FLD and HCC. Analysis of TIA1 expression in mouse and human models of FLD and HCC indicated that TIA1 is downregulated in human HCC. In vivo silencing of TIA1 using AAV8-delivered shRNAs in mice worsens hepatic steatosis and fibrosis induced by a methionine and choline-deficient diet and increases the hepatic tumor burden in liver-specific PTEN knockout (LPTENKO) mice. In contrast, our in vitro data indicated that TIA1 expression promoted proliferation and migration in HCC cell lines, thus suggesting a dual and context-dependent role for TIA1 in tumor initiation versus progression. Consistent with a dual function of TIA1 in tumorigenesis, translatome analysis revealed that TIA1 appears to control the expression of both pro- and anti-tumorigenic factors in hepatic cancer cells. This duality of TIA1′s function in hepatocarcinogenesis calls for cautiousness when considering TIA1 as a therapeutic target or biomarker in HCC.

RNA-assisted sequestration of RNA-binding proteins by cytoplasmic inclusions of the C-terminal 35-kDa fragment of TDP-43.

TDP-43 (also known as TARDBP) is a nuclear splicing factor functioning in pre-mRNA processing. Its C-terminal 35-kDa fragment (TDP-35) forms inclusions or aggregates in cytoplasm, and sequesters full-length TDP-43 into the inclusions through binding with RNA. We extended the research to investigate whether TDP-35 inclusions sequester other RNA-binding proteins (RBPs) and how RNA-binding specificity has a role in this sequestration process. We have characterized T-cell restricted intracellular antigen-1 (TIA1) and other RBPs that can be sequestered into the TDP-35 inclusions through specific RNA binding, and found that this sequestration leads to the dysfunction of TIA1 in maturation of target pre-mRNA. Moreover, we directly visualized the dynamic sequestration of TDP-43 by the cytoplasmic TDP-35 inclusions by live-cell imaging. Our results demonstrate that TDP-35 sequesters some specific RBPs and this sequestration is assisted by binding with RNA in a sequence-specific manner. This study provides further evidence in supporting the hijacking hypothesis for RNA-assisted sequestration and will be beneficial to further understanding of the TDP-43 proteinopathies.

Structural characterization of fibrils formed by the low complexity domain of the RNA-binding protein TIA-1

Proteins containing low complexity sequence domains harbor mutations genetically linked to neurodegenerative diseases, such as amyotrophic lateral sclerosis (ALS) and frontal temporal dementia (FTD). Not much is known about the structures these protein domains adopt functionally and what role the mutations play in causing disease. One key protein with mutations present in the low complexity domain (LCD) is T-cell restricted intracellular antigen-1 (TIA1), which forms fibril-like structures that are usually associated with disease.

SpTIA-1 suppresses WSSV infection by promoting apoptosis in mud crab (Scylla paramamosain)

TIA-1 (T cell restricted intracellular antigen-1) is a kind of RNA-binding protein which serves as the downstream of CED-9 (a BCL2 homolog) and induces apoptosis under stress conditions. So far, the function of apoptosis mediated by TIA-1 has been extensively studied in higher animals, and apoptosis happens to be related to biological immune defense. However, the involvement of TIA-1 in the study of immune function during viral infection has not been clearly studied, especially in marine invertebrates. In the study, SpTIA-1 in mud crab (Scylla paramamosain) was specifically identified. The Open Reading Frame (ORF) of SpTIA-1 was consisted of 1116 nucleotide bases and encoded 372 amino acids. Besides, the results showed that the expression of SpTIA-1 was obviously up-regulated during WSSV (White Spot Syndrome Virus) infection in hemocytes of mud crab. Furthermore, through RNAi approach, we found that SpTIA-1 could activate Caspase-3 signaling and increase ROS levels to reduce mitochondrial membrane potential, resulting in the increase of apoptosis rate in hemocytes, which eventually suppressed WSSV multiplication in mud crab. The current study therefore improves the knowledge of antiviral immunity in mud crab and provides new insights into the innate immunity of marine crustaceans.

Expression Pattern of MicroRNA-21 during the Liver Ischemia/Reperfusion.

Ischemia/reperfusion (I/R) injury in cadaveric liver transplantation is not avoidable. Liver I/R injury is an important phenomenon in hepatic damage. MicroRNA-21 (miR-21) plays an important role in I/R injury. The present study aimed to determine the expression pattern of miR-21 in liver I/R injury/recovery and its correlation with the immunologic transmission signals pathways several days post-reperfusion. In an animal model for I/R in the liver, 40 male Balb/c mice were divided into 3 groups. The animals were monitored for 3 and 24 hours, and also for 4, 7, 14, and 28 days post-reperfusion. Liver tissue damage was assessed by histopathology. The plasma alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and total antioxidant capacity (TAC) levels were measured with enzymatic assays. MiR-21, programmed cell death 4 (PDCD4) mRNA, T-cell-restricted intracellular antigen 1 (TIA1) mRNA, and fas ligand (FASL) mRNA expression levels were measured; using reverse transcription-polymerase chain reaction (RT-PCR) at different times after the reperfusion in liver tissue and blood. Histopathology and plasma ALT, AST, ALP, and TAC levels confirmed liver damage induced by I/R injury. MiR-21 increased by twofold in the liver tissue and on the inflammatory phase after 24 hours of reperfusion; it then continued to decrease up to day 7 post-reperfusion. Afterward, it continued to rise slightly up to day 14 post-reperfusion. This trend was in parallel with the recovery of the liver damage. MiR-21 expression level in the liver and blood is a predictor of the extent of I/R injury.

Multisystem proteinopathy: Where myopathy and motor neuron disease converge.

Multisystem proteinopathy (MSP) is a pleiotropic group of inherited disorders that cause neurodegeneration, myopathy, and bone disease, and share common pathophysiology. Originally referred to as inclusion body myopathy associated with Paget disease of bone and frontotemporal dementia (IBMPFD), attributed to mutations in the gene encoding valosin-containing protein (VCP), it has more recently been discovered that there are several other genes responsible for similar clinical and pathological phenotypes with muscle, brain, nerve, and bone involvement, in various combinations. These include heterogeneous nuclear ribonucleoprotein A2B1 and A1 (hnRNPA2B1, hnRNPA1), sequestosome 1 (SQSTM1), matrin 3 (MATR3), T-cell restricted intracellular antigen 1 (TIA1), and optineurin (OPTN), all of which share disruption of RNA stress granule function and autophagic degradation. This review will discuss each of the genes implicated in MSP, exploring the molecular pathogenesis, clinical features, current standards of care, and future directions for this diverse yet mechanistically linked spectrum of disorders.

Multiple distinct pathways lead to hyperubiquitylated insoluble TDP-43 protein independent of its translocation into stress granules

Multiple distinct pathways lead to hyperubiquitylated insoluble TDP-43 protein independent of its translocation into stress granules

F45. Genetic analysis of TIA1 gene in Chinese patients with amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive lethal neurodegenerative disorder characterized by affecting the upper and lower motor neurons of the brain, brainstem and spinal cord. Approximately 15% of ALS patients also suffering from frontotemporal dementia (FTD). Very recently, six missense mutations affecting the low-complexity domain (LCD) of T cell-restricted intracellular antigen-1 (TIA1) were identified in 1039 non-Hispanic white ALS and ALS-FTD patients. Mutations in the TIA1 gene were suggest to account for ∼2% FALS and <0.5% sporadic ALS (SALS). Those data suggest that TIA1 mutations might be a rare cause of ALS ± FTD. Studies analyzing Asian ALS patient cohorts have not been reported. Previous studies have shown that mutations in the ALS causal genes varied among ethnic populations, such as the G4C2 repeat expansion in the C9orf72 gene is rare in Asian people. To investigate the frequency and spectrum of TIA1 mutations further, we firstly performed mutational screening of TIA1 in a large cohort of ALS/ALS-FTD patients of Chinese origin. The study included 576 Chinese ALS/ALS-FTD patients (FALS = 28; SALS = 535; ALS-FTD = 13) and 500 neurologically normal control subjects. All participants were of Han descent and from mainland China. ALS/ALS-FTD patients were registered at ALS clinic of Neurology Department, Peking Union Medical College Hospital from January 2016 to August 2017. TIA1 (NM_022173) exons 11, 12 and 13 encoding the prion-like LCD domain of TIA1 were sequenced in all 576 cases. Resulting chromatograms were aligned to reference human genome ( UCSC hg19) using CodonCode Aligner tool. All patients harboring mutations of the TIA1 were examined other common ALS causal genes including SOD1, ANXA11, FUS, OPTN, UBQLN2, TARDB and C9orf72. Besides, the identified mutations were subsequently screened in 500 controls. TIA1 sequence analysis revealed a novel heterozygous missense mutation, c.973A>G (p.N325D), in a sporadic ALS case. The variant was not present in our 500 neurologically normal controls as well as several public data bases includingExAC, gnomAD, 1000 Genomes Project and SNP150. The p.N325D substitution affects an highly conserved amino acid in the prion-like LCD domain. Moreover, Four distinct programs – PolyPhen2, Mutation Taster, SIFT and CADD – all predicted p.N325D as a damaging mutation. In conclusion, we have identified a novel mutation in the TIA1 gene in SALS patients of Chinese origin. Our findings provide an overview of the TIA1 mutation in Chinese ALS patients. We propose that the TIA1 mutation is not a frequent mutation in Chinese ALS patients.

Clinical and neuropathological features of ALS/FTD with TIA1 mutations

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) represent a disease continuum with common genetic causes and molecular pathology. We recently identified mutations in the T-cell restricted intracellular antigen-1 (TIA1) protein as a cause of ALS +/− FTD. TIA1 is an RNA-binding protein containing a low complexity domain (LCD) that promotes the assembly of membrane-less organelles, such as stress granules (SG). Whole exome sequencing of two family members with fALS/FTD revealed a novel missense mutation in the TIA1 LCD (P362L). Subsequent screening identified five more TIA1 mutations in six additional ALS patients, but none in controls. All mutation carriers presented with weakness, behavioral abnormalities or language impairments and had a final diagnosis of ALS +/− FTD. Autopsy on five TIA1 mutation carriers showed widespread neurodegeneration with TDP-43 pathology. Round eosinophilic inclusions in lower motor neurons were a consistent feature. Cellular assays revealed abnormal SG dynamics in the presence of TIA1 mutations. In summary, missense mutations in the LCD of TIA1 are a newly recognized cause of ALS/FTD with TDP-43 pathology and strengthen the role of RNA metabolism in the pathogenesis in this disease.

Genetic analysis of TIA1 gene in Chinese patients with amyotrophic lateral sclerosis

Mutations in the low-complexity domain (LCD) of T cell-restricted intracellular antigen-1 (TIA1) was recently identified to be associated with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) in non-Hispanic white populations. We sequenced the TIA1 exons 11-13 encoding LCD in a series of 588 Chinese ALS/ALS-FTD patients (Familial ALS= 29; Sporadic ALS= 546; ALS-FTD= 13) and 500 neurologically normal control subjects. We found a novel heterozygous missense mutation (c.973A>G, p.N325D) in a sporadic ALS patient, which suggests that TIA1 LCD mutations are not common in Chinese ALS/ALS-FTD.

Mutation analysis of the TIA1 gene in Chinese patients with amyotrophic lateral sclerosis and frontotemporal dementia

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the progressive loss of motor neurons in the brain and spinal cord. Frontotemporal dementia (FTD) is a group of dementia syndromes characterized by the progressive deterioration of behaviors, executive dysfunction, and verbal impairment. Increasing evidence indicates that these 2 diseases share a common genetic etiology and pathophysiological mechanism. Recently, rare mutations in the low-complexity domain of the RNA-binding protein T-cell–restricted intracellular antigen-1 (TIA1) gene were identified in Caucasian ALS and ALS-FTD patients. However, no comprehensive mutation analysis of the TIA1 gene has been performed in Chinese patients with ALS and FTD. In this study, we screened the low-complexity domain of TIA1 in a cohort of 241 ALS and 51 FTD patients in mainland China. As a result, 2 novel missense mutations (p.P352L and p.I300T) were identified in 2 sporadic patients with ALS, while no mutation was found in FTD cases. To the best of our knowledge, this report presented the first mutation analysis of the TIA1 gene in patients with ALS and FTD in Chinese population. Our findings broaden the known mutational spectrum in patients with ALS and further confirm TIA1 as a novel causative gene of ALS.

Clinical and neuropathological features of ALS/FTD with TIA1 mutations

Mutations in the stress granule protein T-cell restricted intracellular antigen 1 (TIA1) were recently shown to cause amyotrophic lateral sclerosis (ALS) with or without frontotemporal dementia (FTD). Here, we provide detailed clinical and neuropathological descriptions of nine cases with TIA1 mutations, together with comparisons to sporadic ALS (sALS) and ALS due to repeat expansions in C9orf72 (C9orf72+). All nine patients with confirmed mutations in TIA1 were female. The clinical phenotype was heterogeneous with a range in the age at onset from late twenties to the eighth decade (mean = 60 years) and disease duration from one to 6 years (mean = 3 years). Initial presentation was either focal weakness or language impairment. All affected individuals received a final diagnosis of ALS with or without FTD. No psychosis or parkinsonism was described. Neuropathological examination on five patients found typical features of ALS and frontotemporal lobar degeneration (FTLD-TDP, type B) with anatomically widespread TDP-43 proteinopathy. In contrast to C9orf72+ cases, caudate atrophy and hippocampal sclerosis were not prominent. Detailed evaluation of the pyramidal motor system found a similar degree of neurodegeneration and TDP-43 pathology as in sALS and C9orf72+ cases; however, cases with TIA1 mutations had increased numbers of lower motor neurons containing round eosinophilic and Lewy body-like inclusions on HE stain and round compact cytoplasmic inclusions with TDP-43 immunohistochemistry. Immunohistochemistry and immunofluorescence failed to demonstrate any labeling of inclusions with antibodies against TIA1. In summary, our TIA1 mutation carriers developed ALS with or without FTD, with a wide range in age at onset, but without other neurological or psychiatric features. The neuropathology was characterized by widespread TDP-43 pathology, but a more restricted pattern of neurodegeneration than C9orf72+ cases. Increased numbers of round eosinophilic and Lewy-body like inclusions in lower motor neurons may be a distinctive feature of ALS caused by TIA1 mutations.

TIA1 is a gender-specific disease modifier of a mild mouse model of spinal muscular atrophy

Spinal muscular atrophy (SMA) is caused by deletions or mutations of Survival Motor Neuron 1 (SMN1) gene. The nearly identical SMN2 cannot compensate for SMN1 loss due to exon 7 skipping. The allele C (C+/+) mouse recapitulates a mild SMA-like phenotype and offers an ideal system to monitor the role of disease-modifying factors over a long time. T-cell-restricted intracellular antigen 1 (TIA1) regulates SMN exon 7 splicing. TIA1 is reported to be downregulated in obese patients, although it is not known if the effect is gender-specific. We show that female Tia1-knockout (Tia1−/−) mice gain significant body weight (BW) during early postnatal development. We next examined the effect of Tia1 deletion in novel C+/+/Tia1−/− mice. Underscoring the opposing effects of Tia1 deletion and low SMN level on BW gain, both C+/+ and C+/+/Tia1−/− females showed similar BW gain trajectory at all time points during our study. We observed early tail necrosis in C+/+/Tia1−/− females but not in males. We show enhanced impairment of male reproductive organ development and exacerbation of the C+/+/Tia1−/− testis transcriptome. Our findings implicate a protein factor as a gender-specific modifier of a mild mouse model of SMA.

TIA1 Mutations in Amyotrophic Lateral Sclerosis and Frontotemporal Dementia Promote Phase Separation and Alter Stress Granule Dynamics

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) are age-related neurodegenerative disorders with shared genetic etiologies and overlapping clinical and pathological features. Here we studied a novel ALS/FTD family and identified the P362L mutation in the low-complexity domain (LCD) of Tcell-restricted intracellular antigen-1 (TIA1). Subsequent genetic association analyses showed an increased burden of TIA1 LCD mutations in ALS patients compared to controls (p= 8.7× 10-6). Postmortem neuropathology of five TIA1 mutations carriers showed a consistent pathological signature with numerous round, hyaline, TAR DNA-binding protein 43 (TDP-43)-positive inclusions. TIA1 mutations significantly increased the propensity of TIA1 protein to undergo phase transition. In live cells, TIA1 mutations delayed stress granule (SG) disassembly and promoted the accumulation of non-dynamic SGs that harbored TDP-43. Moreover, TDP-43 in SGs became less mobile and insoluble. The identification of TIA1 mutations in ALS/FTD reinforces the importance of RNA metabolism and SG dynamics in ALS/FTD pathogenesis.

TIA-1 RRM23 binding and recognition of target oligonucleotides.

TIA-1 (T-cell restricted intracellular antigen-1) is an RNA-binding protein involved in splicing and translational repression. It mainly interacts with RNA via its second and third RNA recognition motifs (RRMs), with specificity for U-rich sequences directed by RRM2. It has recently been shown that RRM3 also contributes to binding, with preferential binding for C-rich sequences. Here we designed UC-rich and CU-rich 10-nt sequences for engagement of both RRM2 and RRM3 and demonstrated that the TIA-1 RRM23 construct preferentially binds the UC-rich RNA ligand (5΄-UUUUUACUCC-3΄). Interestingly, this binding depends on the presence of Lys274 that is C-terminal to RRM3 and binding to equivalent DNA sequences occurs with similar affinity. Small-angle X-ray scattering was used to demonstrate that, upon complex formation with target RNA or DNA, TIA-1 RRM23 adopts a compact structure, showing that both RRMs engage with the target 10-nt sequences to form the complex. We also report the crystal structure of TIA-1 RRM2 in complex with DNA to 2.3 Å resolution providing the first atomic resolution structure of any TIA protein RRM in complex with oligonucleotide. Together our data support a specific mode of TIA-1 RRM23 interaction with target oligonucleotides consistent with the role of TIA-1 in binding RNA to regulate gene expression.

PTB and TIAR binding to insulin mRNA 3'- and 5'UTRs; implications for insulin biosynthesis and messenger stability.

ObjectivesInsulin expression is highly controlled on the posttranscriptional level. The RNA binding proteins (RBPs) responsible for this result are still largely unknown.Methods and resultsTo identify RBPs that bind to insulin mRNA we performed mass spectrometry analysis on proteins that bound synthetic oligonucloetides mimicing the 5′- and the 3′-untranslated regions (UTRs) of rat and human insulin mRNA in vitro. We observed that the RBPs heterogeneous nuclear ribonucleoprotein (hnRNP) U, polypyrimidine tract binding protein (PTB), hnRNP L and T-cell restricted intracellular antigen 1-related protein (TIA-1-related protein; TIAR) bind to insulin mRNA sequences, and that the in vitro binding affinity of these RBPs changed when INS-1 cells were exposed to glucose, 3-isobutyl-1-methylxanthine (IBMX) or nitric oxide. High glucose exposure resulted in a modest increase in PTB and TIAR binding to an insulin mRNA sequence. The inducer of nitrosative stress DETAnonoate increased markedly hnRNP U and TIAR mRNA binding. An increased PTB to TIAR binding ratio in vitro correlated with higher insulin mRNA levels and insulin biosynthesis rates in INS-1 cells. To further investigate the importance of RNA-binding proteins for insulin mRNA stability, we decreased INS-1 and EndoC-βH1 cell levels of PTB and TIAR by RNAi. In both cell lines, decreased levels of PTB resulted in lowered insulin mRNA levels while decreased levels of TIAR resulted in increased insulin mRNA levels. Thapsigargin-induced stress granule formation was associated with a redistribution of TIAR from the cytosol to stress granules.ConclusionsThese experiments indicate that alterations in insulin mRNA stability and translation correlate with differential RBP binding. We propose that the balance between PTB on one hand and TIAR on the other participates in the control of insulin mRNA stability and utilization for insulin biosynthesis.

TIA-1 and TIAR interact with 5′-UTR of enterovirus 71 genome and facilitate viral replication

Enterovirus 71 is one of the major causative pathogens of HFMD in children. Upon infection, the viral RNA is translated in an IRES-dependent manner and requires several host factors for effective replication. Here, we found that T-cell-restricted intracellular antigen 1 (TIA-1), and TIA-1 related protein (TIAR) were translocated from nucleus to cytoplasm after EV71 infection and localized to the sites of viral replication. We found that TIA-1 and TIAR can facilitate EV71 replication by enhancing the viral genome synthesis in host cells. We demonstrated that both proteins bound to the stem-loop I of 5′-UTR of viral genome and improved the stability of viral genomic RNA. Our results suggest that TIA-1 and TIAR are two new host factors that interact with 5-UTR of EV71 genome and positively regulate viral replication.