MAGI3 Suppresses Glioma Cell Proliferation via Upregulation of PTEN Expression.

OBJECTIVE: To investigate the role and molecular mechanism of membrane-associated guanylate kinase inverted 3 (MAGI3) in glioma cell proliferation. METHODS: The expression levels of MAGI3 and PTEN were assessed in glioma samples by Western blotting. MAGI3 was stably transfected into C6 glioma cells to obtain C6-MAGI3 cells. Then, the proliferation, the expression levels of MAGI3 and PTEN, and Akt phosphorylation were evaluated in C6 and C6-MAGI3 cells. Xenograft tumor models were established by subcutaneous injection of C6 and C6-MAGI3 cells into nude mice, and the growth rates of xenografts in the mice were compared. The potential role of MAGI3 expression in PI3K/Akt signaling activation was further investigated by examining the correlation between MAGI3 expression and the expression of PI3K/Akt signaling downstream target genes in a glioma dataset using gene set enrichment analysis (GSEA). RESULTS: Expression levels of MAGI3 and PTEN were significantly downregulated in gliomas. Overexpression of MAGI3 in the glioma C6 cell line upregulated PTEN protein expression, inhibited the phosphorylation of Akt, and suppressed cell proliferation. MAGI3 overexpression also inhibited the growth of C6 glioma tumor xenografts in nude mice. Analysis based on the GEO database confirmed the negative correlation between activation of PI3K/Akt pathway and MAGI3 mRNA levels in human glioma samples. CONCLUSION: The loss of MAGI3 expression in glioma may enhance the proliferation of glioma cells via downregulation of PTEN expression, leading to the activation of the PI3K/Akt pathway. MAGI3 is a potential glioma suppressor.

[Regulation on EGFR function via its interacting proteins and its potential application].

Epidermal growth factor receptor (EGFR) is imptortant for cell activities, oncogenesis and cell migration, and EGFR inhibitor can treat cancer efficiently, but its side effects, for example, in skin, limited its usage. On the other hand, EGFR interacting proteins may also lead to oncogenesis and its interacting protein as drug targets can avoid cutaneous side effect, which implies possibly a better outcome and life quality of cancer patients. For the multiple EGFR interaction proteins, B1R enhances Erk/MAPK signaling, while PTPN12, Kek1, CEACAM1 and NHERF repress Erk/MAPK signaling. CaM may alter charge of EGFR juxamembrane domain and regulate activation of PI3K/Akt and PLC-gamma/PKC. STAT1, STAT5b are widely thought to be activated by EGFR, while there is unexpectedly inhibiting sequence within EGFR to repress the activity of STATs. LRIG1 and ACK1 enhance the internalization and degration of EGFR, while NHERF and HIP1 repress it. In this article, proteins interacting with EGFR, their interacting sites and their regulation on EGFR signal transduction will be reviewed.

Alpha(1D)-adrenergic receptor insensitivity is associated with alterations in its expression and distribution in cultured vascular myocytes.

AIM: It is unclear why alpha(1D)-adrenergic receptors (alpha(1D)-ARs) play a critical role in the mediation of peripheral vascular resistance and blood pressure in situ but function inefficiently when studied in vitro. The present study examined the causes for these inconsistencies in native alpha(1)-adrenergic functional performance between the vascular smooth muscle and myocytes. METHODS: The alpha(1)-adrenergic mediated contraction, Ca(2+) signaling and the subcellular receptor distribution were evaluated using the Fluo-4, BODIPY-FL prazosin and subtype-specific antibodies. RESULTS: Rat aortic rings and freshly dissociated myocytes displayed contractile and increased intracellular Ca(2+) responses to stimulation with phenylephrine (PE, 10 micromol), respectively. However, the PE-induced responses disappeared completely in cultured aortic myocytes, whereas PE-enhanced Ca(2+) transients were seen in cultured rat cardiac myocytes. Further studies indicated that alpha(1D)-ARs, the major receptor subtype responsible for the alpha(1)-adrenergic regulation of aortic contraction, were distributed both intracellularly and at the cell membrane in freshly dispersed aortic myocytes, similar to the alpha(1A)-AR subcellular localization in the cultured cardiomyocytes. In the cultured aortic myocytes, however, in addition to a marked decrease in their protein expression relative to the aorta, most labeling signals for alpha(1D)-ARs were found in the cytoplasm. Importantly, treating the culture medium with charcoal/dextran caused the reappearance of alpha(1D)-ARs at the cell surface and a partial restoration of the Ca(2+) signal response to PE in approximately 30% of the cultured cells. CONCLUSION: Reduction in alpha(1D)-AR total protein expression and disappearance from the cell surface contribute to the insensitivity of cultured vascular smooth muscle cells to alpha(1)-adrenergic receptor activation.

Hippocampal protein levels related to spatial memory are different in the Barnes maze and in the multiple T-maze.

The Multiple T-maze (MTM) and the Barnes maze (BM) are land mazes used for the evaluation of spatial memory. The observation that mice are performing differently in individual mazes made us test the hypothesis that differences in cognitive performances in the two land mazes would be accompanied by differences in hippocampal protein levels. C57BL/6J mice were tested in the BM and in the MTM, hippocampi were extirpated 6 h following the probe trials each, and proteins were extracted for gel-based proteomic analysis. Mice learned the task in both paradigms. Levels of hippocampal proteins from several pathways including signaling, chaperone, and metabolic cascades were significantly different between the two spatial memory tasks. Protein levels were linked to spatial memory specifically as yoked controls were used.