ABSTRACT
The scaffold protein IRS-1 is an essential node in insulin/IGF signaling. It has long been recognized that the stability of IRS-1 is dependent on its endomembrane targeting. However, how IRS-1 targets the intracellular membrane, and what type of intracellular membrane is actually targeted, remains poorly understood. Here, we found that the phase separation-mediated IRS-1 puncta attached to endoplasmic reticulum (ER). VAPB, an ER-anchored protein that mediates tethers between ER and membranes of other organelles, was identified as a direct interacting partner of IRS-1. VAPB mainly binds active IRS-1 because IGF-1 enhanced the VAPB-IRS-1 association and replacing of the nine tyrosine residues of YXXM motifs disrupted the VAPB-IRS-1 association. We further delineated that the Y745 and Y746 residues in the FFAT-like motif of IRS-1 mediated the association with VAPB. Notably, VAPB targeted IRS-1 to the ER and subsequently maintained its stability. Consistently, ablation of VAPB in mice led to downregulation of IRS-1, suppression of insulin signaling, and glucose intolerance. The amyotrophic lateral sclerosis (ALS)-derived VAPB P56S mutant also impaired IRS-1 stability by interfering with the ER-tethering of IRS-1. Our findings thus revealed a previously unappreciated condensate-membrane contact (CMC), by which VAPB stabilizes the membraneless IRS-1 signalosome through targeting it to ER membrane.
ABSTRACT
The present study aimed to investigate the association of the invasiveness of colon cancer (CC) with the expression of CCAAT/enhancer binding protein α (C/EBPα). Immunohistochemistry was performed to determine the expression of C/EBPα in the cancer and adjacent tissue samples from 48 patients with CC. A pCDGFP-C/EBPα eukaryotic expression vector was constructed, and a wound-healing assay was performed to observe the effect of transfection on the migration of SW480 cells. In addition, the expression levels of tumor invasion-associated proteins, including Kruppel-like factor 5 (KLF5), matrix metallopeptidase (MMP)-2, MMP-9, and E-cadherin (ECD) were detected subsequent to transfection. Immunohistochemistry analysis demonstrated that the rate of low C/EBPα expression in normal tissue was 6.25%, whereas the rate in CC tissues was 68.75%; this difference was statistically significant (P<0.05). The patients with lower C/EBPα expression exhibited statistically larger tumor diameters, more advanced tumor-node-metastasis (TMN) stages and a greater likelihood of lymph node metastasis. The overexpression of C/EBPα significantly reduced the mobility of SW480 cells, and the expression of KLF5, MMP-2 and MMP-9 was reduced, whereas the expression of ECD was increased. In conclusion, C/EBPα was downregulated in CC tissue samples, and associated with the TMN stage and metastasis of CC; in addition, the overexpression of C/EBPα significantly reduced the invasiveness of CC cells. This may be significant for the diagnosis and treatment of CC in the future.
ABSTRACT
OBJECTIVE: To investigate the biomechanical effect of anterior screw fixation on the type II fractured odontoid process. METHODS: Twenty fresh human C1-C2 vertebrae specimens were harvested and randomly divided into three groups. The angle of type II fracture line was 0 degree in group I (n=6), 17 degrees in group II (n=8) and 25 degrees in group III (n=6). The fractures were treated by anterior screw fixation. Insertion torque,maximal axial pullout force and stiffness of the bone-screw were tested. RESULTS: There was no significant difference of screw insertion torque and the pull-out strength between each group. The displacement of the odontoid fragment had an association to the angle of the fracture line,the displacement of the small angle was significantly higher than that of the large one (P < 0.5). No significant difference of structure stiffness of the bone-screw was found between each group. CONCLUSION: Anterior screw fixation is feasible for type II odontoid fracture with certain fracture line extends from anteroinferior to posterosuperior.
