OBJECTIVETo investigate the role of cytoplasmic domain of integrin alpha IIb in platelet signal transduction.

METHODSBinding capacity of integrin alpha IIb(R995A) to antibody platelet activation complex-1 (PAC-1) and pp125 focal adhesion kinase (FAK) phosphorylation of cells were detected by flow cytometry, immune precipitation, and Western blotting.

RESULTSWithout activation, wild-type alpha IIb beta3 Chinese hamster ovary (CHO) cells failed to bind to PAC-1, but mutant chimera alpha IIb(R995A)beta3 CHO cells were able to bind with PAC-1. Furthermore, phosphorylation of pp125 (FAK) in wild-type alpha IIb beta3 CHO cells occured only when cells were adhered to fibrinogen, but could not be detected in bovine serum albumin suspension. However in the mutant chimera group, it could be detected in both conditions.

CONCLUSIONThe mutation in integrin alpha IIb(R995A) alters its affinity state as a receptor, thus also mediating cytoplasmic signal transduction leading to the phosphorylation of pp125 (FAK) without ligand binding.

Animals ; Blood Platelets ; metabolism ; CHO Cells ; Cell Adhesion ; Cricetinae ; Cricetulus ; Cytoplasm ; metabolism ; Dual Specificity Phosphatase 2 ; Focal Adhesion Kinase 1 ; Focal Adhesion Protein-Tyrosine Kinases ; Humans ; Phosphorylation ; Platelet Glycoprotein GPIIb-IIIa Complex ; genetics ; metabolism ; physiology ; Point Mutation ; Protein Phosphatase 2 ; Protein Tyrosine Phosphatases ; metabolism ; Protein-Tyrosine Kinases ; metabolism ; Signal Transduction ; Transfection

Animals ; Calcium ; metabolism ; DNA-Binding Proteins ; metabolism ; Enzyme Activation ; Focal Adhesion Kinase 2 ; metabolism ; Gene Expression Regulation, Viral ; Hepatitis B virus ; genetics ; physiology ; Humans ; Signal Transduction ; Trans-Activators ; genetics ; metabolism ; Virus Replication

Objective: To uncover the time-dependent expression pattern of ptk2b gene and ptk2b-encoded protein, protein tyrosine kinase 2 beta(PTK2B), in the brain tissues of transgenic animal models of Alzheimer's disease (AD) and its relationship with the levels of Aβ_1-42, phosphorylation of Tau (p-Tau) and low density lipoprotein receptor-related protein-1(LRP-1) in blood and brain tissues. Methods: In this study, 5-, 10- and 15-month-old APPswe/PS1dE9 double-transgenic mice harboring the genotype of AD confirmed by the gene test were divided into the 5-, 10- and 15-month-old experiment groups, and simultaneously, age-matched C57BL/6J mice were placed into the corresponding control groups, with 8 mice in each group. All mice were subjected to the Morris Water Maze for test of cognitive and behavioral ability. Expression profiles of PTK2B, Aβ_1-42, p-Tau/Tau and LRP-1 in the hippocampus or blood of mice were quantified by using the immunohistochemistry staining, Western blot or enzyme-linked immunosorbent assay (ELISA), while the mRNA expression of ptk2b in the hippocampus was quantified by using the real-time quantitative polymerase chain reaction (qRT-PCR). Results: Results of experiment groups demonstrated that as mice aged, the expression levels of PTK2B, ptk2b mRNA, Aβ_1-42 and p-Tau/Tau in the hippocampus were increased, and the expression of LRP-1 was decreased gradually. While in the blood, the level of Aβ_1-42 was decreased, and the cognitive and behavioral ability was decreased in an age-dependent manner (all P＜ 0.05). However, comparisons among the control groups, only the age-dependent downregulation of LRP-1 were observed in hippocampus(P＜0.05), but other indicators had no significant differences (P＞0.05). Conclusion: In the hippocampus of APP/PS1 double-transgenic mice, the expressions of PTK2B, Aβ_1-42 and p-Tau/Tau are upregulated, LRP-1 is downregulated, while cognitive and behavioral ability is decreased, and such changes are presented in a time-dependent manner.
Alzheimer Disease/metabolism* ; Amyloid beta-Peptides ; Amyloid beta-Protein Precursor/genetics* ; Animals ; Focal Adhesion Kinase 2/metabolism* ; Hippocampus/metabolism* ; Low Density Lipoprotein Receptor-Related Protein-1 ; Maze Learning ; Mice ; Mice, Inbred C57BL ; Mice, Transgenic ; RNA, Messenger

CD98, a disulfide-linked 125-kDa heterodimeric type II transmembrane glycoprotein, regulates beta 1 integrin- mediated cell adhesion. However, the molecular mechanisms underlying CD98-mediated activation of beta 1 integrin are presently unclear. In this study, the effects of CD98 signaling on the expression and clustering of beta 1 integrin were investigated. Activation of CD98 augmented surface expression of beta 1 integrin on MCF-7 cells. Cross-linking CD98 induced clustering of beta 1 integrins. Inhibition of phosphorylation of focal adhesion kimase (FAK) by PP2, an inhibitor of Src family kinase, reduced cell-extracellular matrix adhesion, but not surface expression and clustering of beta1 integrin on MCF-7 cells. This result was confirmed by over-expression of dominant negative forms of FAK. In addition, phalloidin or cytochalasin D inhibited CD98-mediated induction of cell-ECM adhesion, but not surface expression and clustering of b1 integrins. The inhibitory effects of PP2, cytochalasin D or phalloidin on CD98-stimulated cell adhesion were diminished by pretreatment of cells with Mn2+, which is shown to induce conformational change of integrins. These results provide the first evidence that CD98 activation increases not only beta1 integrin affinity but also its surface expression and clustering and the latter is independent of FAK/Src and cytoskeleton.
Antigens, CD29/*biosynthesis/genetics ; Antigens, CD98/agonists/*metabolism ; Cell Line, Tumor ; Cytochalasin D/pharmacology ; Cytoskeleton/drug effects/enzymology ; Focal Adhesion Kinase 2/genetics/*metabolism ; Focal Adhesions/drug effects/enzymology ; Humans ; Microscopy, Confocal ; Multiprotein Complexes/*biosynthesis/genetics ; Mutant Proteins/genetics/metabolism ; Phalloidine/pharmacology ; Phosphorylation/drug effects ; Protein Binding ; Pyrimidines/pharmacology ; Signal Transduction/physiology ; Transfection

OBJECTIVETo study the role of inhibition FAK expression by FAK siRNA in liver cancer cell (MHCC97-H) adhesion, invasion and cytoskeleton rearrangement.

METHODSFAK siRNA was transfected into MHCC97-H cell by Lipofectamine 2000; then, FAK expression was detected by Western blot analysis. The change of cell adhesive and invasive ability after RNAi was checked by cell adhesive assay and cell invasive assay respectively. Meanwhile, matrix metalloproteinase-2 secretion was checked by gelatin zymography. Cytoskeleton rearrangement labeled by immunofluorescence antibody was examined by confocal laser scanning microscope.

RESULTSFAK expression in MHCC97-H cell was obviously inhibited by specific FAK siRNA; However, it was not inhibited by negative siRNA. Adhesion rate between MHCC97-H cell and extracellular matrix decreased from 57.3% to 35.8% after RNA interference (P < 0.05). Compared with untreated group, the number of cell penetrating matrigel also decreased from 31.3 +/- 2.6 to 14.5 +/- 3.1 after transfection (P < 0.05). Besides, matrix metalloproteinase-2 secretion was significantly reduced for FAK expression inhibited by FAK siRNA. FAK inhibition influenced Vinculin rearrangement, blocked the formation of lamellipodium, delayed the time of focal adhesion formation.

CONCLUSIONDown-regulation the expression of FAK can reduce adhesive rate and invasive number of MHCC97-H cell by influencing cytoskeleton rearrangement and decreasing matrix metalloproteinase-2 secretion.

Blotting, Western ; Carcinoma, Hepatocellular ; enzymology ; genetics ; pathology ; Cell Adhesion ; Cell Line, Tumor ; Cell Movement ; Cytoskeleton ; metabolism ; Fluorescent Antibody Technique ; Focal Adhesion Kinase 1 ; genetics ; metabolism ; Humans ; Liver Neoplasms ; enzymology ; genetics ; pathology ; Matrix Metalloproteinase 2 ; metabolism ; Microscopy, Confocal ; RNA Interference ; RNA, Small Interfering ; genetics ; Transfection ; methods

OBJECTIVETo investigate the expression of SOCS3 and Pyk2 and their correlations in non-small cell lung cancer (NSCLC).

METHODSThe expression of SOCS3 and Pyk2 was detected in 100 cases of NSCLC, human bronchial epithelial cells (HBE) and 6 lung cancer cell lines by immunohistochemistry and immunofluorescence staining. The methylation status of SOCS3 was investigated in A549 cells by methylation-specific PCR. A549 cells were either treated with a demethylation agent 5-aza-2'-deoxycytidine (5-aza) or transfected with three SOCS3 mutants with various functional domains deleted. Besides, the cells were pretreated with a proteasome inhibitor β-lactacystin where indicated. The effects of SOCS3 on Pyk2 expression, Pyk2 Tyr 402 and ERK1/2 phosphorylations were assessed by Western blot. RT-PCR was used to estimate Pyk2 mRNA levels. Transwell experiments were performed to evaluate cell migration.

RESULTSSOCS3 (43.0%, 43/100) and Pyk2 (65.0%, 65/100) were expressed in NSCLC. A significant negative correlation was found between SOCS3 and Pyk2 in both NSCLC tissues and cell lines. SOCS3 was aberrantly methylated and 5-aza restored SOCS3 expression. Transfection studies indicated that exogenous SOCS3 interacted with Pyk2, and both Src homology 2 (SH2) and kinase inhibitory region (KIR) domains contributed to Pyk2 binding. Furthermore, SOCS3 was found to inhibit Pyk2-associated ERK1/2 activity in A549 cells. SOCS3 possibly promoted degradation of Pyk2 in a SOCS-box-dependent manner and interfered with cell migration.

CONCLUSIONSThe data indicates that SOCS3 definitely plays roles in regulating Pyk2 signaling, and cell motility. Decreased SOCS3 induced by methylation may confer a migration advantage to A549 cells.

Adenocarcinoma ; genetics ; metabolism ; pathology ; Carcinoma, Non-Small-Cell Lung ; genetics ; metabolism ; pathology ; Carcinoma, Squamous Cell ; genetics ; metabolism ; pathology ; Cell Line, Tumor ; Cell Movement ; DNA Methylation ; Focal Adhesion Kinase 2 ; metabolism ; Humans ; Lung Neoplasms ; genetics ; metabolism ; pathology ; Lymphatic Metastasis ; Mutation ; Phosphorylation ; Signal Transduction ; Suppressor of Cytokine Signaling 3 Protein ; Suppressor of Cytokine Signaling Proteins ; genetics ; metabolism