Deactivation of TBP contributes to SCA17 pathogenesis.

Spinocerebellar ataxia type 17 (SCA17) is an autosomal dominant cerebellar ataxia caused by the expansion of polyglutamine (polyQ) within the TATA box-binding protein (TBP). Previous studies have shown that polyQ-expanded TBP forms neurotoxic aggregates and alters downstream genes. However, how expanded polyQ tracts affect the function of TBP and the link between dysfunctional TBP and SCA17 is not clearly understood. In this study, we generated novel Drosophila models for SCA17 that recapitulate pathological features such as aggregate formation, mobility defects and premature death. In addition to forming neurotoxic aggregates, we determined that polyQ-expanded TBP reduces its own intrinsic DNA-binding and transcription abilities. Dysfunctional TBP also disrupts normal TBP function. Furthermore, heterozygous dTbp amorph mutant flies exhibited SCA17-like phenotypes and flies expressing polyQ-expanded TBP exhibited enhanced retinal degeneration, suggesting that loss of TBP function may contribute to SCA17 pathogenesis. We further determined that the downregulation of TBP activity enhances retinal degeneration in SCA3 and Huntington's disease fly models, indicating that the deactivation of TBP is likely to play a common role in polyQ-induced neurodegeneration.

Arabidopsis CIA2 and CIL have distinct and overlapping functions in regulating chloroplast and flower development.

Arabidopsis CHLOROPLAST IMPORT APPARATUS 2 (CIA2) and its paralogous protein CIA2-LIKE (CIL) are nuclear transcription factors containing a C-terminal CCT motif. CIA2 promotes the expression of nuclear genes encoding chloroplast-localized translocons and ribosomal proteins, thereby increasing the efficiency of protein import and synthesis in chloroplasts. We have previously reported that CIA2 and CIL form a homodimer or heterodimer through their C-terminal sequences and interact with other nuclear proteins, such as CONSTANS (CO), via their N-terminal sequences, but the function of CIL had remained unclear. In this study, we verified through transgenic cia2 mutant plants expressing the CIL coding sequence that CIL is partially functionally redundant to CIA2 during vegetative growth. We also compared phenotypes and gene expression profiles of wildtype Col-0, cia2, cil, and cia2/cil mutants. Our results indicate that CIA2 and CIL coordinate chloroplast biogenesis and function mainly by upregulating the expression of the nuclear factor GOLDEN2-LIKE 1 (GLK1) and chloroplast transcription-, translation-, protein import-, and photosynthesis-related genes, with CIA2 playing a more crucial role. Furthermore, we compared flowering phenotypes in single, double, and triple mutant plants of co, cia2, and cil. We found that CIA2 and CIL participate in modulating long-day floral development. Notably, CIA2 increases flower number and height of the inflorescence main axis, whereas CIL promotes flowering.

Protein disulfide isomerase a4 promotes lung cancer development via the Stat3 pathway in stromal cells.

BACKGROUND: Protein disulfide isomerases a4 (Pdia4) is known to be involved in cancer development. Our previous publication showed that Pdia4 positively promotes cancer development via its inhibition of procaspase-dependent apoptosis in cancer cells. However, nothing is known about its role in the cancer microenvironment. RESULTS: Here, we first found that Pdia4 expression in lung cancer was negatively correlated with patient survival. Next, we investigated the impact of host Pdia4 in stromal cells during cancer development. We showed that Pdia4 was expressed at a low level in stromal cells, and this expression was up-regulated akin to its expression in cancer cells. This up-regulation was stimulated by tumour cell-derived stimuli. Genetics studies in tumour-bearing wild-type and Pdia4-/- mice showed that host Pdia4 promoted lung cancer development in the mice via cancer stroma. This promotion was abolished in Rag1-/- mice which lacked T and B cells. This promotion could be restored once T and B cells were added back to Rag1-/- mice. In addition, host Pdia4 positively regulated the number and immunosuppressive function of stromal cells. Mechanistic studies showed that host Pdia4 positively controlled the Stat3/Vegf pathway in T and B lymphocytes via its stabilization of activated Stat3 in a Thioredoxin-like domain (CGHC)-dependent manner. CONCLUSIONS: These findings identify Pdia4 as a possible target for intervention in cancer stroma, suggesting that targeting Pdia4 in cancer stroma is a promising anti-cancer approach.

Pdia4 regulates ß-cell pathogenesis in diabetes: molecular mechanism and targeted therapy.

Loss of ß-cell number and function is a hallmark of diabetes. ß-cell preservation is emerging as a promising strategy to treat and reverse diabetes. Here, we first found that Pdia4 was primarily expressed in ß-cells. This expression was up-regulated in ß-cells and blood of mice in response to excess nutrients. Ablation of Pdia4 alleviated diabetes as shown by reduced islet destruction, blood glucose and HbA1c, reactive oxygen species (ROS), and increased insulin secretion in diabetic mice. Strikingly, this ablation alone or in combination with food reduction could fully reverse diabetes. Conversely, overexpression of Pdia4 had the opposite pathophysiological outcomes in the mice. In addition, Pdia4 positively regulated ß-cell death, dysfunction, and ROS production. Mechanistic studies demonstrated that Pdia4 increased ROS content in ß-cells via its action on the pathway of Ndufs3 and p22phox . Finally, we found that 2-ß-D-glucopyranosyloxy1-hydroxytrideca 5,7,9,11-tetrayne (GHTT), a Pdia4 inhibitor, suppressed diabetic development in diabetic mice. These findings characterize Pdia4 as a crucial regulator of ß-cell pathogenesis and diabetes, suggesting Pdia4 is a novel therapeutic and diagnostic target of diabetes.

Sequence analysis and protein interactions of Arabidopsis CIA2 and CIL proteins.

BACKGROUND: A previous screening of Arabidopsis thaliana for mutants exhibiting dysfunctional chloroplast protein transport identified the chloroplast import apparatus (cia) gene. The cia2 mutant has a pale green phenotype and reduced rate of protein import into chloroplasts, but leaf shape and size are similar to wild-type plants of the same developmental stage. Microarray analysis showed that nuclear CIA2 protein enhances expression of the Toc75, Toc33, CPN10 and cpRPs genes, thereby up-regulating protein import and synthesis efficiency in chloroplasts. CIA2-like (CIL) shares 65% sequence identity to CIA2, suggesting that CIL and CIA2 are homologous proteins in Arabidopsis. Here, we further assess the protein interactions and sequence features of CIA2 and CIL. RESULTS: Subcellular localizations of truncated CIA2 protein fragments in our onion transient assay demonstrate that CIA2 contains two nuclear localization signals (NLS) located at amino acids (aa) 62-65 and 291-308, whereas CIL has only one NLS at aa 47-50. We screened a yeast two-hybrid (Y2H) Arabidopsis cDNA library to search for putative CIA2-interacting proteins and identified 12 nuclear proteins, including itself, CIL, and flowering-control proteins (such as CO, NF-YB1, NF-YC1, NF-YC9 and ABI3). Additional Y2H experiments demonstrate that CIA2 and CIL mainly interact with flowering-control proteins via their N-termini, but preferentially form homo- or hetero-dimers through their C-termini. Moreover, sequence alignment showed that the N-terminal sequences of CIA2, CIL and NF-YA are highly conserved. Therefore, NF-YA in the NF-Y complex could be substituted by CIA2 or CIL. CONCLUSIONS: We show that Arabidopsis CIA2 and CIL can interact with CO and NF-Y complex, so not only may they contribute to regulate chloroplast function but also to modulate flower development.