Heme oxygenase-1 (HO-1) has anti-apoptotic and anti-inflammatory effects. In this study, the HO-1 gene was delivered into the brain using dexamethasone-conjugated polyamidoamine generation 2 (PAMAM G2-Dexa) for the treatment of ischemic stroke. PAMAM G2-Dexa formed stable complexes with plasmid DNA (pDNA). The pDNA delivery efficiency of PAMAM G2-Dexa was higher than that of polyethylenimine (PEI25k, 25 kDa), dexamethasone-conjugated PEI (PEI-Dexa), and PAMAM G2 in Neuro2A cells. Therapeutic effect of PAMAM G2-Dexa/pHO-1 complexes was evaluated in a stroke animal model. PAMAM G2-Dexa delivered pHO-1 more efficiently into the ischemic brain than PEI25k and PEI-Dexa with higher therapeutic effect. Therefore, PAMAM G2-Dexa/pHO-1 complexes may be useful for ischemic stroke gene therapy.

No abstract

Stress granules (SGs) are membraneless cytosolic granules containing dense aggregations of RNA-binding proteins and RNAs. They appear in the cytosol under stress conditions and inhibit the initiation of mRNA translation. SGs are dynamically assembled under stressful conditions and rapidly disassembled after stress removal. They are heterogeneous in their RNA and protein content and are cell type- and stress-specific. In post-mitotic neurons, which do not divide, the dynamics of neuronal SGs are tightly regulated, implying that their dysregulation leads to neurodegeneration. Mutations in RNA-binding proteins are associated with SGs. SG components accumulate in cytosolic inclusions in many neurodegenerative diseases, such as frontotemporal dementia and amyotrophic lateral sclerosis. Although SGs primarily mediate a pro-survival adaptive response to cellular stress, abnormal persistent SGs might develop into aggregates and link to the pathogenesis of diseases. In this review, we present recent advances in the study of neuronal SGs in physiology and pathology, and discuss potential therapeutic approaches to remove abnormal, persistent SGs associated with neurodegeneration.

C-terminal fragments of Tar DNA-binding protein 43 (TDP-43) have been identified as the major pathological protein in several neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). However, how they affect cellular toxicity and neurodegeneration, including the modulation process remains unknown. This study revealed that the C-terminal fragment of TDP-43 (TDP-25) was localized primarily to mitochondria and caused abnormal mitochondrial morphology, inducing Parkin-mediated mitophagy. Also, we discovered that the knockdown of selective autophagy receptors, such as TAX1BP, Optineurin, or NDP52 caused TDP-25 accumulation, indicating that TDP-25 was degraded by mitophagy. Interestingly, myosin IIB, a nonmuscle type of myosin and actin-based motor protein, is mostly colocalized to TDP-25 associated with abnormal mitochondria. In addition, myosin IIB inhibition by siRNA or blebbistatin induced mitochondrial accumulation of insoluble TDP-25 and Tom20, and reduced neuronal cell viability. Our results suggest a novel role of myosin IIB in mitochondrial degradation of toxic TDP-25. Therefore, we proposed that regulating myosin IIB activity might be a potential therapeutic target for neurodegenerative diseases associated with TDP-43 pathology.

The bacterial effector protein RavZ is secreted by the intracellular pathogen Legionella pneumophila and inhibits host autophagy through an irreversible deconjugation of mammalian ATG8 (mATG8) proteins from autophagosome membranes. However, the roles of the LC3 interacting region (LIR) motifs in RavZ function remain unclear. In this study, we show that a membrane-targeting (MT) domain or the LIR motifs of RavZ play major or minor roles in RavZ function. A RavZ mutant that does not bind to mATG8 delipidated all forms of mATG8-phosphatidylethanolamine (PE) as efficiently as did wild-type RavZ. However, a RavZ mutant with a deletion of the MT domain selectively delipidated mATG8-PE less efficiently than did wild-type RavZ. Taken together, our results suggest that the effects of LIR motifs and the MT domain on RavZ activity are complementary and work through independent pathways.