Expression and sub-cellular localization of leucine-rich repeats and immunoglobulin-like domains are related to antioxidant enzymes in human ependymoma and oligodendroglioma

The current study investigated correlations between the expression of leucine-rich repeats and immunoglobulin-like domain 1 （LRIG1） and antioxidant enzymes and related proteins, including manganese superoxide dismutase, glutamate cysteine ligase catalytic or regulatory subunit, thioredoxin and thioredoxin reductase, in both human ependymoma and oligodendroglioma. Results revealed that the cytoplasmic expression of LRIG1 was associated with expression of glutamate cysteine ligase catalytic subunit in the human ependymoma, while the nuclear expression of LRIG1 was associated with expression of thioredoxin reductase. In human oligodendroglioma, the cytoplasmic expression of LRIG1 was associated with expression of the glutamate cysteine ligase catalytic subunit. Both the nuclear and perinuclear expressions of LRIG1 were associated with expression of glutamate cysteine ligase regulatory subunit. These results indicated that several antioxidant enzymes and related proteins contributed to LRIG1 expression, and that these may participate in the antioxidation of the cells.

Increased leucine-rich repeats and immunoglobulin- like domains 1 expression enhances chemosensitivity in glioma

Leucine-rich repeats and immunoglobulin-like domains 1 （LRIG1） is an anti-oncogene. LRIG1 is correlated with Bcl-2 in ependymomas. Decreased Bcl-2 and manganese superoxide dismutase expression can improve the chemosensitivity of glioma. In the present study, a tissue microarray of human brain astrocytomas was constructed. To investigate the relationship of LRIG1 with Bcl-2 and manganese superoxide dismutase, LRIG1, Bcl-2 and manganese superoxide dismutase expression in our tissue microarray was determined using immunohistochemistry. In addition, we constructed the LRIG1-U251 cell line, and its responses to doxorubicin and temozolomide were detected using the MTT assay. Results showed that LRIG1 expression was significantly negatively correlated with Bcl-2 and manganese superoxide dismutase expression in glioma. Also, proliferation of LRIG1-U251 cells exposed to doxorubicin or temozolomide was significantly inhibited, i.e. in the LRIG1-U251 cell line, the chemosensitivity to doxorubicin and temozolomide was increased. This indicates that increased LRIG1 expression produces a chemosensitivity in glioma.

Axonal growth inhibitors and their receptors in spinal cord injury:from biology to clinical translation

Axonal growth inhibitors are released during traumatic injuries to the adult mammalian central nervous system, including after spinal cord injury. These molecules accumulate at the injury site and form a highly inhibitory environment for axonal regeneration. Among these inhibitory molecules, myelinassociated inhibitors, including neurite outgrowth inhibitor A, oligodendrocyte myelin glycoprotein, myelin-associated glycoprotein, chondroitin sulfate proteoglycans and repulsive guidance molecule A are of particular importance. Due to their inhibitory nature, they represent exciting molecular targets to study axonal inhibition and regeneration after central injuries. These molecules are mainly produced by neurons, oligodendrocytes, and astrocytes within the scar and in its immediate vicinity. They exert their effects by binding to specific receptors, localized in the membranes of neurons. Receptors for these inhibitory cues include Nogo receptor 1, leucine-rich repeat, and Ig domain containing 1 and p75 neurotrophin receptor/tumor necrosis factor receptor superfamily member 19(that form a receptor complex that binds all myelin-associated inhibitors), and also paired immunoglobulin-like receptor B. Chondroitin sulfate proteoglycans and repulsive guidance molecule A bind to Nogo receptor 1, Nogo receptor 3, receptor protein tyrosine phosphatase σ and leucocyte common antigen related phosphatase, and neogenin, respectively. Once activated, these receptors initiate downstream signaling pathways, the most common amongst them being the Rho A/ROCK signaling pathway. These signaling cascades result in actin depolymerization, neurite outgrowth inhibition, and failure to regenerate after spinal cord injury. Currently, there are no approved pharmacological treatments to overcome spinal cord injuries other than physical rehabilitation and management of the array of symptoms brought on by spinal cord injuries. However, several novel therapies aiming to modulate these inhibitory proteins and/or their receptors are under investigation in ongoing clinical trials. Investigation has also been demonstrating that combinatorial therapies of growth inhibitors with other therapies, such as growth factors or stem-cell therapies, produce stronger results and their potential application in the clinics opens new venues in spinal cord injury treatment.

Effect of Over-expressed LRIG3 on Cell Cycle and Survival of Glioma Cells

This study examined the effects of over-expression of leucine-rich repeats and immunoglobulin-like domains 3 （LRIG3） on the cell cycle and survival of human glioma cell line U87 and U251 and explored the possible mechanisms. The LRIG3 gene was transduced into U87 and U251 cells respectively by using lentivirus and the transduced cells were selected by puromycin. The changes in LRIG3 mRNA and protein levels were measured by RT-PCR and Western blotting. The apoptosis rate was detected by Annexin Ⅴ-FITC/PI double labeling and the cell cycle was flow cytometrically analyzed. Compared with control cells, LRIG3 mRNA expression in U251 and U87 cells transduced with pLVX-DsRed-LRIG3-Monomer-N1 were increased by 77.6% and 129.7%, and LRIG3 protein expression was raised by 141.3% and 322.7%, respectively. Cell cycle analysis showed that LRIG3 over-expression increased the percentage of cells at G0/G1 phase （P〈0.01）. Over-expressed LRIG3 could significantly promote the apoptosis of U87 and U251 cells （P〈0.05）. These findings suggest that the over-expression of LRIG3 could arrest the cell cycle in G0/G1 phase, and promote apoptosis of U87 and U251 cells.

Extracellular and cytoplasmic regions of LRIG1 play a negative role in EGFR activity: Findings of a radioligand-binding assay

Objective Leucine-rich repeats and immunoglobulin-like domains 1(LRIG1) is a newly identified human gene that inhibits the epidermal growth factor receptor(EGFR), which on combining with a ligand, can drive tumor growth. This study investigated the interaction between human LRIG1 and EGFR and attempted to delineate the functions of as well as the mechanisms used by the extracellular(ECD) and cytoplasmic(CPD) domains of the human LRIG1 protein to downregulate human EGFR signaling activity.Methods Two constructed chimeric eukaryotic expression vectors, pIRES2-EGFP-3XFLAG-LRIG1-ET and p3FLAG-LRIG1-TC, encoding the extracellular and transmembrane regions(LRIG1-ET) and the transmembrane and cytoplasmic regions(LRIG1-TC), respectively, and the plasmid p3XFLAG-CMV-9-LRIG1 encoding full-length LRIG1(LRIG1-FL) were transfected into the human glioma cell line U251 or primary astrocytoma cells by using liposomes. The number and affinity of cell surface EGFR on transfected cells was determined by ^(125)I-EGF binding assay. Results The dissociation constant(KD) values for EGFR were higher, and the maximum increase was observed in the cells transfected into LRIG1-ET(1.36 folds). The number of maximal binding sites(Bmax) of the receptors was decreased in all transfected cells; the maximum decrease was noted in the cells transfected into LRIG1-FL(40.05%).Conclusion Both the ECD and CPD of LRIG1 are important to negate EGFR signaling. The ECD may interfere with the binding between EGFR and its ligand and facilitate the functions of CPD. The CPD may, when brought in proximity to EGFR, enhance receptor degradation. These two mechanisms can contribute to the downregulation of EGFR-mediated signaling by LRIG1.