Cullin 5 gene expression in the rat cerebral cortex and hippocampus following traumatic brain injury (TBI)

Protective effects and regulatory pathways of melatonin in traumatic brain injury mice model: Transcriptomics and bioinformatics analysis

Traumatic brain injury (TBI) is the leading cause of disability and mortality globally. Melatonin (Mel) is a neuroendocrine hormone synthesized from the pineal gland that protects against TBI. Yet, the precise mechanism of action is not fully understood. In this study, we examined the protective effect and regulatory pathways of melatonin in the TBI mice model using transcriptomics and bioinformatics analysis. The expression profiles of mRNA, long non-coding RNA (lncRNA), microRNA (miRNA), and circular RNA (circRNA) were constructed using the whole transcriptomes sequencing technique. In total, 93 differentially expressed (DE) mRNAs (DEmRNAs), 48 lncRNAs (DElncRNAs), 59 miRNAs (DEmiRNAs), and 59 circRNAs (DEcircRNAs) were identified by the TBI mice with Mel treatment compared to the group without drug intervention. The randomly selected coding RNAs and non-coding RNAs (ncRNAs) were identified by quantitative real-time polymerase chain reaction (qRT-PCR). To further detect the biological functions and potential pathways of those differentially expressed RNAs, Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analyses were executed. In our research, the regulatory network was constructed to show the relationship of lncRNA-RBPs. The lncRNA-mRNA co-expression network was established based on the Pearson coefficient to indicate the expression correlations. Moreover, the DEcircRNA–DEmiRNA–DEmRNA and DElncRNA–DEmiRNA–DEmRNA regulatory networks were constructed to demonstrate the regulatory relationship between ncRNAs and mRNA. Finally, to further verify our predicted results, cytoHubba was used to find the hub gene in the synaptic vesicle cycle pathway, and the expression level of SNAP-25 and VAMP-2 after melatonin treatment were detected by Western blotting and immunofluorescence. To sum up, these data offer a new insight regarding the molecular effect of melatonin treatment after TBI and suggest that the high-throughput sequencing and analysis of transcriptomes are useful for studying the drug mechanisms in treatment after TBI.

Cullin-RING Ligase 5: Functional characterization and its role in human cancers

Cullin-RING ligase 5 (CRL5) is a multi-protein complex and consists of a scaffold protien cullin 5, a RING protein RBX2 (also known as ROC2 or SAG), adaptor proteins Elongin B/C, and a substrate receptor protein SOCS. Through targeting a variety of substrates for proteasomal degradation or modulating various protein-protein interactions, CRL5 is involved in regulation of many biological processes, such as cytokine signal transduction, inflammation, viral infection, and oncogenesis. As many substrates of CRL5 are well-known oncoproteins or tumor suppressors, abnormal regulation of CRL5 is commonly found in human cancers. In this review, we first briefly introduce each of CRL5 components, and then discuss the biological processes regulated by four members of SOCS-box-containing substrate receptor family through substrate degradation. We next describe how CRL5 is hijacked by a variety of viral proteins to degrade host anti-viral proteins, which facilitates virus infection. We further discuss the regulation of CUL5 and its various roles in human cancers, acting as either a tumor suppressor or an oncoprotein in a context-dependent manner. Finally, we propose novel insights for future perspectives on the validation of cullin5 and other CRL5 components as potential targets, and possible targeting strategies to discover CRL5 inhibitors for anti-cancer and anti-virus therapies.

Effects of DHA on Hippocampal Autophagy and Lysosome Function After Traumatic Brain Injury

Traumatic brain injury (TBI) triggers endoplasmic reticulum (ER) stress and impairs autophagic clearance of damaged organelles and toxic macromolecules. In this study, we investigated the effects of the post-TBI administration of docosahexaenoic acid (DHA) on improving hippocampal autophagy flux and cognitive functions of rats. TBI was induced by cortical contusion injury in Sprague-Dawley rats, which received DHA (16 mg/kg in DMSO, intraperitoneal administration) or vehicle DMSO (1 ml/kg) with an initial dose within 15 min after the injury, followed by a daily dose for 3 or 7 days. First, RT-qPCR reveals that TBI induced a significant elevation in expression of autophagy-related genes in the hippocampus, including SQSTM1/p62 (sequestosome 1), lysosomal-associated membrane proteins 1 and 2 (Lamp1 and Lamp2), and cathepsin D (Ctsd). Upregulation of the corresponding autophagy-related proteins was detected by immunoblotting and immunostaining. In contrast, the DHA-treated rats did not exhibit the TBI-induced autophagy biogenesis and showed restored CTSD protein expression and activity. T₂-weighted images and diffusion tensor imaging (DTI) of ex vivo brains showed that DHA reduced both gray matter and white matter damages in cortical and hippocampal tissues. DHA-treated animals performed better than the vehicle control group on the Morris water maze test. Taken together, these findings suggest that TBI triggers sustained stimulation of autophagy biogenesis, autophagy flux, and lysosomal functions in the hippocampus. Swift post-injury DHA administration restores hippocampal lysosomal biogenesis and function, demonstrating its therapeutic potential.

The role of cullin 5-containing ubiquitin ligases

The suppressor of cytokine signaling (SOCS) box consists of the BC box and the cullin 5 (Cul5) box, which interact with Elongin BC and Cul5, respectively. SOCS box-containing proteins have ubiquitin ligase activity mediated by the formation of a complex with the scaffold protein Cul5 and the RING domain protein Rbx2, and are thereby members of the cullin RING ligase superfamily. Cul5-type ubiquitin ligases have a variety of substrates that are targeted for polyubiquitination and proteasomal degradation. Here, we review the current knowledge on the identification of Cul5 and the regulation of its expression, as well as the signaling pathways regulated by Cul5 and how viruses highjack the Cul5 system to overcome antiviral responses.

Military personnel with chronic symptoms following blast traumatic brain injury have differential expression of neuronal recovery and epidermal growth factor receptor genes

Objective: Approximately one-quarter of military personnel who deployed to combat stations sustained one or more blast-related, closed-head injuries. Blast injuries result from the detonation of an explosive device. The mechanisms associated with blast exposure that give rise to traumatic brain injury (TBI), and place military personnel at high risk for chronic symptoms of post-concussive disorder (PCD), post-traumatic stress disorder (PTSD), and depression are not elucidated.

Methods: To investigate the mechanisms of persistent blast-related symptoms, we examined expression profiles of transcripts across the genome to determine the role of gene activity in chronic symptoms following blast-TBI. Active duty military personnel with (1) a medical record of a blast-TBI that occurred during deployment (n = 19) were compared to control participants without TBI (n = 17). Controls were matched to cases on demographic factors including age, gender, and race, and also in diagnoses of sleep disturbance, and symptoms of PTSD and depression. Due to the high number of PCD symptoms in the TBI+ group, we did not match on this variable. Using expression profiles of transcripts in microarray platform in peripheral samples of whole blood, significantly differentially expressed gene lists were generated. Statistical threshold is based on criteria of 1.5 magnitude fold-change (up or down) and p-values with multiple test correction (false discovery rate <0.05).

Results: There were 34 transcripts in 29 genes that were differentially regulated in blast-TBI participants compared to controls. Up-regulated genes included epithelial cell transforming sequence and zinc finger proteins, which are necessary for astrocyte differentiation following injury. Tensin-1, which has been implicated in neuronal recovery in pre-clinical TBI models, was down-regulated in blast-TBI participants. Protein ubiquitination genes, such as epidermal growth factor receptor, were also down-regulated and identified as the central regulators in the gene network determined by interaction pathway analysis.

Conclusion: In this study, we identified a gene-expression pathway of delayed neuronal recovery in military personnel a blast-TBI and chronic symptoms. Future work is needed to determine if therapeutic agents that regulate these pathways may provide novel treatments for chronic blast-TBI-related symptoms.

Cullin5 reduces retinal cell death induced by glutamate toxicity

PURPOSE

To investigate the expression in the mouse retina and the function in a retinal cell of cullin5 that is known as a protein that is associated with ubiquitilation.

METHODS

The retinal sites of expressing cullin5 were determined by immunohistochemistry with a specific antibody for cullin5. Retinal cells were transfected with HA-tagged cullin5 using an adenovirus system, and retinal cells were exposed to L-glutamate with or without an over-expression of cullin5.

RESULTS

Cullin5 was expressed in the retina of C57BL/6N mice and the retinal ganglion cell layer (RGL) of retina was strongly immunostained. Further, cullin5 was localized in the retinal ganglion cell (RGC). An over-expression of cullin5 reduced the percentage of retinal cell deaths induced by L-glutamate.

CONCLUSIONS

The expression of cullin5 on retinal cells and reduction in the percentage of dead retinal cells induced by L-glutamate suggest that cullin5 has neuroprotective properties in retinal cells.

Granulocytic differentiation of HL-60 promyelocytic leukemia cells is associated with increased expression of Cul5

The human HL-60 promyelocytic leukemia cell line has been widely used as a model for studying granulocytic differentiation. All-trans retinoic acid (ATRA) treatment of HL-60 cells promotes granulocytic differentiation and is effective as differentiation therapy for patients with acute promyelocytic leukemia. The identification of genes that are transcriptionally regulated by ATRA has provided insight into granulocytic differentiation and differentiation therapy. The Asb-2 (ankyrin repeat SOCS box 2) gene has previously been identified as a transcriptional target in ATRA-treated HL-60 cells. The ASB-2 protein forms an E3 ubiquitin ligase complex with the proteins, Cul5, regulator of cullin 2 (ROC2), and elongin B and C. The purpose of this study was to determine if there is increased expression of Cul5 during granulocytic differentiation of HL-60 cells. To induce granulocytic differentiation, HL-60 cells were treated for 5 d with ATRA and differentiation was confirmed by examining superoxide anion production, nuclear morphology, and changes in the expression of CD11b, CD13, and CD15. Quantitative real-time RT-PCR was used to measure Cul5 mRNA expression and also the expression of other components of the E3 ubiquitin ligase (ASB-2, ROC2, elongin B and C). Granulocytic differentiation of HL-60 cells was associated with a 1.6-, 1.7-, and 23-fold statistically significant (P <or= 0.05) increase in mRNA expression for Cul5, ROC2, and ASB-2, respectively. No significant change was found in elongin B and C mRNA expression. Using Western blot analysis, the expression of Cul5 protein was increased 6.5-fold with granulocytic differentiation of the HL-60 cells. Increased expression of multiple components of the Cul5-containing E3 ubiquitin ligase complex with ATRA treatment of HL-60 cells indicates that this complex may play an important role in granulocytic differentiation.

Alterations of cerebral cortex and hippocampal proteasome subunit expression and function in a traumatic brain injury rat model

Following cellular stress or tissue injury, the proteasome plays a critical role in protein degradation and signal transduction. The present study examined the beta-subunit expression of constitutive proteasomes (beta1, beta2, and beta5), immunoproteasomes (beta1i, beta2i, and beta5i) and the 11S proteasome activator, PA28alpha, in the rat CNS after traumatic brain injury (TBI). Concomitant measures assessed changes in proteasome activities. Quantitative real time PCR results indicated that beta1 and beta2 mRNA levels were not changed, while beta5 mRNA levels were significantly decreased in injured CNS following TBI. However, beta1i, beta2i, beta5i, and PA28alpha mRNA levels were significantly increased in the injured CNS. Western blotting studies found that beta1, beta2, beta5, beta2i, and beta5i subunit protein levels remained unchanged in the injured CNS, but beta1i and PA28alpha protein levels were significantly elevated in ipsilateral cerebral cortex and hippocampus. Proteasome activity assays found that peptidyl glutamyl peptide hydrolase-like and chymotrypsin-like activity were significantly reduced in the CNS after TBI, and that trypsin-like proteasome activity was increased in the injured cerebral cortex. Our results demonstrated that both proteasome composition and function in the CNS were affected by trauma. Treatments that preserve proteasome function following CNS injury may be beneficial as an approach to cerebral neuroprotection.

Ubiquitin and ubiquitin-conjugated protein expression in the rat cerebral cortex and hippocampus following traumatic brain injury (TBI)

Regulation of protein turnover is essential to the survival of eukaryotic cells. This important cellular process is partly regulated by the ubiquitin-proteasome system through posttranslational modification by the conjugation of ubiquitin chains to proteins targeted for degradation by proteasomes. The present study examined ubiquitin mRNA and protein expression in the CNS of rats that sustained traumatic brain injury (TBI). Quantitative real-time polymerase chain reaction results indicated that mRNA levels of ubA52, ubB and ubC in the ipsilateral cerebral cortex were significantly decreased on Day 1 post-TBI, that ubC mRNA levels also were significantly lower than control on Day 3 post-TBI, but that by Day 7 post-TBI, ubA52, ubB and ubC mRNA levels had all returned to control levels. In the ipsilateral hippocampus, ubA52 mRNA levels were significantly lower on Days 1-7 post-TBI, while ubB and ubC mRNA levels were less only on Day 1 post-TBI. Western blotting found that free ubiquitin protein levels were significantly reduced in both ipsilateral cerebral cortex and hippocampus on Days 1-7 post-TBI, while there was markedly increased ubiquitin-conjugated protein in ipsilateral cerebral cortex on Day 7 and in hippocampus on Days 3-7 post-TBI. Our study suggests that altered ubiquitin system function in the CNS contributes to the pathological outcomes of TBI.

Delayed increase of tyrosine hydroxylase expression in rat nigrostriatal system after traumatic brain injury

Tyrosine hydroxylase (TH) is the key enzyme for synthesizing dopamine (DA) in dopaminergic neurons and its terminals. Emerging experimental and clinical evidence support the hypothesis of a disturbance in dopamine neurotransmission following traumatic brain injury (TBI). However, the effect of controlled cortical impact (CCI) injury on TH in the nigrostriatal system is currently unknown. To determine if there is an alteration in TH after CCI injury, we examined TH levels at 1 day, 7 days, and 28 days post-injury by utilizing a commercially available antibody specific to TH. Rats were anesthetized and surgically prepared for CCI injury (4 m/s, 3.2 mm) or sham surgery. Injured (N=6) and sham animals (N=6) were sacrificed and coronally sectioned (35 microm thick) through the striatum and substantia nigra (SN) for immunohistochemistry. Additionally, semiquantitative measurements of TH protein in striatal and SN homogenates from injured (N=6) and sham (N=6) rats sacrificed at the appropriate time post-surgery were assessed using Western blot analysis. TH protein is bilaterally increased at 28 days post-injury in nigrostriatal system revealed by immunohistochemistry in injured rats compared to sham controls. Western blot analysis confirms the findings of immunohistochemistry in both striatum and SN. We speculate that the increase in TH in the nigrostriatal system may reflect a compensatory response of dopaminergic neurons to upregulate their synthesizing capacity and a delayed increase in the efficiency of DA neurotransmission after TBI.