Bin Zhang

Beta-cell apoptosis appears to represent a key event in the pathogenesis of type 1 diabetes. Previous studies have demonstrated that administration of the serine proteinase inhibitor alpha1-antitrypsin (AAT) prevents type 1 diabetes development in NOD mice and prolongs islet allograft survival in rodents; yet the mechanisms underlying this therapeutic benefit remain largely unclear. Herein we describe novel findings indicating that AAT significantly reduces cytokine- and streptozotocin (STZ)-induced beta-cell apoptosis. Specifically, strong antiapoptotic activities for AAT (Prolastin, human) were observed when murine insulinoma cells (MIN6) were exposed to tumor necrosis factor-alpha. In a second model system involving STZ-induced beta-cell apoptosis, treatment of MIN6 cells with AAT similarly induced a significant increase in cellular viability and a reduction in apoptosis. Importantly, in both model systems, treatment with AAT completely abolished induced caspase-3 activity. In terms of its activities in vivo, treatment of C57BL/6 mice with AAT prevented STZ-induced diabetes and, in agreement with the in vitro analyses, supported the concept of a mechanism involving the disruption of beta-cell apoptosis. These results propose a novel biological function for this molecule and suggest it may represent an effective candidate for attempts seeking to prevent or reverse type 1 diabetes.

Summary ATP ‐citrate lyases ( ACL ) play critical roles in tumour cell propagation, foetal development and growth, and histone acetylation in human and animals. Here, we report a novel function of ACL in cell death‐mediated pathogen defence responses in rice. Using ethyl methanesulphonate ( EMS ) mutagenesis and map‐based cloning, we identified an Oryza sativa ACL ‐A2 mutant allele, termed spotted leaf 30‐1 ( spl30‐1 ), in which an A‐to‐T transversion converts an Asn at position 343 to a Tyr (N343Y), causing a recessive mutation that led to a lesion mimic phenotype. Compared to wild‐type plants, spl30‐1 significantly reduces ACL enzymatic activity, accumulates high reactive oxygen species and increases degradation rate of nuclear deoxyribonucleic acids. CRISPR /Cas9‐mediated insertion/deletion mutation analysis and complementation assay confirmed that the phenotype of spl30‐1 resulted from the defective function of Os ACL ‐A2 protein. We further biochemically identified that the N343Y mutation caused a significant degradation of SPL 30 N343Y in a ubiquitin‐26S proteasome system ( UPS )‐dependent manner without alteration in transcripts of Os ACL ‐A2 in spl30‐1 . Transcriptome analysis identified a number of up‐regulated genes associated with pathogen defence responses in recessive mutants of Os ACL ‐A2, implying its role in innate immunity. Suppressor mutant screen suggested that Os SL , which encodes a P450 monooxygenase protein, acted as a downstream key regulator in spl30‐1 ‐mediated pathogen defence responses. Taken together, our study discovered a novel role of Os ACL ‐A2 in negatively regulating innate immune responses in rice.