Translocator protein 18 kDa(TSPO): old dogma, new mice, new structure, and new questions for neuroprotection

The normal development and optimal functioning of the brain requires a vigilant immune surveillance system to detect and remove potential risk factors and prevent infection and tissue damage. Microglia are the resident immune cells and the frontline defenders responsible for the immune response of the brain. Resting microglia possess a ramified morphology with numerous thin processes that continuously sample the environment. In response to inflammatory signals, microglia become activated and transform their morphology into a thick, amoeboid-like shape. Activated microglia proliferate, tolerate to sites of iniurv,

Translocator protein ligand, YL-IPA08, attenuates lipopolysaccharide-induced depression-like behavior by promoting neural regeneration

Translocator protein has received attention for its involvement in the pathogenesis of depression. This study assessed the effects of the new translocator protein ligand, YL-IPA08, on alleviating inflammation-induced depression-like behavior in mice and investigated its mechanism of action. Mice were intracerebroventricularly injected with 1, 10, 100 or 1000 ng lipopolysaccharide. The tail-suspension test and the forced swimming test confirmed that 100 ng lipopolysaccharide induced depression-like behavior. A mouse model was then established by intraventricular injection of 100 ng lipopolysaccharide. On days 16-24 after model establishment, mice were intragastrically administered 3 mg/kg YL-IPA08 daily. Immunohistochemistry was used to determine BrdU and NeuN expression in the hippocampus. YL-IPA08 effectively reversed the depression-like behavior of lipopolysaccharide-treated mice, restored body mass, increased the number of BrdU-positive cells, and the number and proportion of BrdU and NeuN double-positive cells. These findings indicate that YL-IPA08 can attenuate lipopolysaccharide-induced depression-like behavior in mice by promoting the formation of hippocampal neurons.

Possible role of translocator protein 18 ku on sepsis associated encephalopathy by mediat⁃ing neuroinflammation

OBJECTIVE To clarify the role of translocator protein 18 ku(TSPO)on cecum liga⁃tion and puncture(CLP)induced sepsis associat⁃ed encephalopathy(SAE)mice,which consis⁃tently demonstrated astrocyte activation and neu⁃roinflammation.Background SAE,a brain dys⁃function,caused by systemic infection without clinical or laboratory evidence of direct infection.Most patients have symptoms such as long-term cognitive dysfunction.As the pathogenesis of SAE is very complex,neuroinflammation for SAE is one of the causes of the disease.TSPO as a marker of neuroinflammation that has the poten⁃tial to regulate neuroinflammation and SAE.METHODS The animal model of SAE was in⁃duced by CLP.TSPO ligands and TSPO knock⁃out mice were used for behavioral and molecular biology research.Survival rate of mice within 120 h on CLP mice was observed.The changes of cog⁃nitive function in mice were observed by Morris water maze and open field test.The changes of proinflammatory factors(IL-1β,TNF-α,IL-6)in hippocampus were observed by ELISA;Astro⁃cyte activation,marked by GFAP,in hippocam⁃pal was analyzed by tissue immunofluorescence and Western blotting.RESULTS Pretreatment with the TSPO ligands,XBD173 or PK11195,sig⁃nificantly improved the survival rate of CLP mice.The results of Morris water maze showed that TSPO ligands significantly increased the number of crossing the platform and the target quadrant time on CLP mice,suggesting that TSPO ligands may improve the learning and memory ability of CLP mice.Subsequent experiments revealed that TSPO ligands can reduce the inflammatory factors(IL-1β,TNF-α,IL-6)and astrocyte activa⁃tion in hippocampus of CLP mice.Similar results were also confirmed in TSPO knockout CLP mice,suggesting intervention of TSPO can reduce neuroinflammatory response and play a protec⁃tive role on SAE mice.CONCLUSION TSPO may play a critical role on SAE mice.Targeting TSPO by pharmacological means may improve the survival rate and cognitive function on CLP mice,which may through inhibiting astrocyte acti⁃vation and neuroinflammation in hippocampal.

Application of modern neuroimaging technology in the diagnosis and study of Alzheimer’s disease

Neurological abnormalities identified via neuroimaging are common in patients with Alzheimer’s disease.However,it is not yet possible to easily detect these abnormalities using head computed tomography in the early stages of the disease.In this review,we evaluated the ways in which modern imaging techniques such as positron emission computed tomography,single photon emission tomography,magnetic resonance spectrum imaging,structural magnetic resonance imaging,magnetic resonance diffusion tensor imaging,magnetic resonance perfusion weighted imaging,magnetic resonance sensitive weighted imaging,and functional magnetic resonance imaging have revealed specific changes not only in brain structure,but also in brain function in Alzheimer’s disease patients.The reviewed literature indicated that decreased fluorodeoxyglucose metabolism in the temporal and parietal lobes of Alzheimer’s disease patients is frequently observed via positron emission computed tomography.Furthermore,patients with Alzheimer’s disease often show a decreased N-acetylaspartic acid/creatine ratio and an increased myoinositol/creatine ratio revealed via magnetic resonance imaging.Atrophy of the entorhinal cortex,hippocampus,and posterior cingulate gyrus can be detected early using structural magnetic resonance imaging.Magnetic resonance sensitive weighted imaging can show small bleeds and abnormal iron metabolism.Task-related functional magnetic resonance imaging can display brain function activity through cerebral blood oxygenation.Resting functional magnetic resonance imaging can display the functional connection between brain neural networks.These are helpful for the differential diagnosis and experimental study of Alzheimer’s disease,and are valuable for exploring the pathogenesis of Alzheimer’s disease.

Molecular Cloning and Sequence Analysis of the Toc33 cDNA in Brassica napus Line Cr3529

Two primers, designed according to the Arabidoposis thaliana Toc33 sequence, were used to amplify the full coding region of the Toc33 cDNAs in leaves of a chlorophyll-reduced (Cr) mutant Cr3529 and its wild type 3529, Brassica napus, by RT-PCR technique. The RT-PCR results showed that the fragment homologous to Toc33 was expressed in Cr3529 as well as 3529 seedlings. PCR fragments were inserted into the pMD18-T vector and transferred into E. coli, then two cDNA clones, BnToc33-c and BnToc33, were obtained. Sequence analysis showed that the two sequences were 894 bp and the nucleotide and the deduced amino acid sequences were highly homologous to those of A. thaliana. There were three diverged nucleotides between the Cr3529 and the 3529 Toc33 cDNAs, i.e., GGT/AGT, TTG/TTT, AGG/AGT, all of which belonged to missense mutation. The amino acid replacement ((Leu/Phe) caused by TTG/TTT mutation located in the membrane anchor domain may result in chlorophyll-reduced character in Cr3529.

Identification of BTG1 Status in Solid Cancer for Future Researches Using a System Review and Meta-analysis

Abundant studies have been conducted to identify how B-cell translocation gene 1 protein(BTG1)gene affects the differentiation,proliferation,metastasis of cancer cells,and how it further regulates the generation or development of diseases to influence the prognosis of patients.However,the data from single research were not powerful enough.The correlations between BTG1 expression and mechanisms of tumorigenesis or prognosis of patients are still in controversial.Our system review and meta-analysis provided a complete explanation about the association between BTG1 expression and clinicopathological features or prognosis of patients,which further laid a foundation for future research on BTG1.Fifteen eligible studies consisting of 1992 participants were included.We uncovered that BTG1 expression in solid tumors was associated w让h lymph node status(RR=0.66,95%CI:0.58-0.75,P=0.142),TMN stage status(RR=2.13,95%CI:1.71-2.65,P=0.001),T category(RR=1.90,95%CI:1.20-3.00,P=0.000),histological differentiation(RR-1.91,95%CI:1.55-2.37,7=0.012),vascular invasion(RR=0.90,95%CI:0.57-1.41,P=0.001).BTG1 low expression was significantly associated with overall survival(OS)(HR=0.47,95%CI:0.38-0.67,P=0.000).It concluded that BTG1 possessed the potential value for future research and could be recommended as a significant biomarker in solid tumor.

Understanding protein translocation across chloroplast membranes:Translocons and motor proteins

Subcellular organelles in eukaryotes are surrounded by lipid membranes.In an endomembrane system,vesicle trafficking is the primary mechanism for the delivery of organellar proteins to specific organelles.However,organellar proteins for chloroplasts,mitochondria,the nucleus,and peroxisomes that are translated in the cytosol are directly imported into their target organelles.Chloroplasts are a plant-specific organelle with outer and inner envelope membranes,a dual-membrane structure that is similar to mitochondria.Interior chloroplast proteins translated by cytosolic ribosomes are thus translocated through TOC and TIC complexes(translocons in the outer and inner envelope of chloroplasts,respectively),with stromal ATPase motor proteins playing a critical role in pulling pre-proteins through these import channels.Over the last three decades,the identity and function of TOC/TIC components and stromal motor proteins have been actively investigated,which has shed light on the action mechanisms at a molecular level.However,there remains some disagreement over the exact composition of TIC complexes and genuine stromal motor proteins.In this review,we discuss recent findings on the mechanisms by which proteins are translocated through TOC/TIC complexes and discuss future prospects for this field of research.

TSPO deficiency exacerbates acute lung injury via NLRP3 inflammasome-mediated pyroptosis

Background:Acute respiratory distress syndrome(ARDS)is a common cause of respiratory failure in many critically ill patients.Although inflammasome activation plays an important role in the induction of acute lung injury(ALI)and ARDS,the regulatory mechanism of this process is still unclear.When cells are stimulated by inflammation,the integrity and physiological function of mitochondria play a crucial part in pyroptosis.However,the underlying mechanisms and function of mitochondrial proteins in the process of pyroptosis are largely not yet known.Here,we identified the 18-kDa translocator protein(TSPO),a mitochondrial outer membrane protein,as an important mediator regulating nucleotide-binding domain,leucine-rich repeat,and pyrin domain-containing protein 3(NLRP3)inflammasome activation in macrophages during ALI.Methods:TSPO gene knockout(KO)and lipopolysaccharide(LPS)-induced ALI/ARDS mouse models were employed to investigate the biological role of TSPO in the pathogenesis of ARDS.Murine macrophages were used to further characterize the effect of TSPO on the NLRP3 inflammasome pathway.Activation of NLRP3 inflammasome was preformed through LPS+adenosine triphosphate(ATP)co-stimulation,followed by detection of mitochondrial membrane potential,reactive oxygen species(ROS)production,and cell death to evaluate the potential biological function of TSPO.Comparisons between two groups were performed with a two-sided unpaired t-test.Results:TSPO-KO mice exhibited more severe pulmonary inflammation in response to LPS-induced ALI.TSPO deficiency resulted in enhanced activation of the NLRP3 inflammasome pathway,promoting more proinflammatory cytokine production of macrophages in LPS-injured lung tissue,including interleukin(IL)-1β,IL-18,and macrophage inflammatory protein(MIP)-2.Mitochondria in TSPO-KO macrophages tended to depolarize in response to cellular stress.The increased production of mitochondrial damage-associated molecular pattern led to enhanced mitochondrial membrane depolarization and pyroptosis in TSPO-KO cells.Conclusion:TSPO may be the key regulator of cellular pyroptosis,and it plays a vital protective role in ARDS occurrence and development.

In Vivo Function of Tic22, a Protein Import Component of the Intermembrane Space of Chloroplasts

Preprotein import into chloroplasts depends on macromolecular machineries in the outer and inner chloroplast envelope membrane （TOC and TIC）. It was suggested that both machineries are interconnected by components of the intermembrane space （IMS）. That is, amongst others, Tic22, of which two closely related isoforms exist in Arabidopsis thaliana, namely atTic22-III and atTic22-IV. We investigated the function of Tic22 in vivo by analyzing T-DNA insertion lines of the corresponding genes. While the T-DNA insertion in the individual genes caused only slight defects, a double mutant of both isoforms showed retarded growth, a pale phenotype under high-light conditions, a reduced import rate, and a reduction in the photosynthetic performance of the plants. The latter is supported by changes in the metabolite content of mutant plants when compared to wild-type. Thus, our results support the notion that Tic22 is directly involved in chloroplast preprotein import and might point to a particular importance of Tic22 in chloroplast biogenesis at times of high import rates.

Elevated Neurosteroids in the Lateral Thalamus Relieve Neuropathic Pain in Rats with Spared Nerve Injury

Neurosteroids are synthesized in the nervous system from cholesterol or steroidal precursors imported from peripheral sources. These compounds are important allosteric modulators of γ-aminobutyric acid A receptors （GABAARs）, which play a vital role in pain modulation in the lateral thalamus, a main gate where somatosensory information enters the cerebral cortex. Using high-perfor mance liquid chromatography/tandem mass spectrometry, we found increased levels of neurosteroids （pregnenolone, progesterone, deoxycorticosterone, allopregnanolone, and tetrahydrodeoxycorticosterone） in the chronic stage of neuropathic pain （28 days after spared nerve injury） in rats.The expression of the translocator protein TSPO, the upstream steroidogenesis rate-limiting enzyme, increased at the same time. In vivo stereotaxic microinjection of neurosteroids or the TSPO activator AC-5216 into the lateral thalamus （AP -3.0 mm, ML 4-3.0 mm, DV 6.0 mm） alleviated the mechanical allodynia in neuropathic pain, while the TSPO inhibitor PK 11195 exacerbated it. The analgesic effects of AC-5216 and neurosteroids were sig- nificantly attenuated by the GABAAR antagonist bicuculline. These results suggested that elevated neurosteroids in the lateral thalamus play a protective role in the chronic stage of neuropathic pain.

Functional Analysis of Semi-conserved Transit Peptide Motifs and Mechanistic Implications in Precursor Targeting and Recognition

Over 95% of plastid proteins are nuclear-encoded as their precursors containing an N-terminal extension known as the transit peptide （TP）. Although highly variable, TPs direct the precursors through a conserved, posttranslational mechanism involving translocons in the outer （TOC） and inner envelope （TOC）. The organelle import specificity is mediated by one or more components of the Toc complex. However, the high TP diversity creates a paradox on how the sequences can be specifically recognized. An emerging model of TP design is that they contain multiple loosely conserved motifs that are recognized at different steps in the targeting and transport process. Bioinformatics has demonstrated that many TPs contain semiconserved physicochemical motifs, termed FGLK. In order to characterize FGLK motifs in TP recognition and import, we have analyzed two well-studied TPs from the precursor of RuBisCO small subunit （SStp） and ferredoxin （Fdtp）. Both SStp and Fdtp contain two FGLK motifs. Analysis of large set mutations （-85） in these two motifs using in vitro, in organello, and in vivo approaches support a model in which the FGLK domains mediate interaction with TOC34 and possibly other TOC components. In vivo import analysis suggests that multiple FGLK motifs are functionally redundant. Furthermore, we discuss how FGLK motifs are required for efficient precursor protein import and how these elements may permit a convergent function of this highly variable class of targeting sequences.