The G1 cytoplasmic tail of Hantaan virus (HTNV) harbors a highly conserved region, which is homologous to immunoreceptor tyrosine-based activation motifs (ITAM) and is termed the ITAM-like sequence. To demonstrate the potential signal-transducing activity of G1 ITAM-like sequence resembling the canonical ITAM within immune and endothelial cells, a series of experiments were performed to define its interaction with cellular kinases. The synthesized G1 ITAM-like peptide was shown to coprecipitate with cellular phosphoprotein complexes by an immune-complex kinase assay. Mutational analyses showed that this ITAM-like sequence was a substrate for the Src family kinase Fyn, and two conserved tyrosine residues were required for coprecipitating Lyn, Syk, and ZAP-70 kinases. These findings demonstrated that HTNV envelope glycoprotein G1 contains a functional ITAM-like sequence in its cytoplasmic tail, which can bind critical cellular kinases that regulate immune and endothelial cell functions.
Amino Acid Sequence ; Cells, Cultured ; Hantaan virus ; chemistry ; physiology ; Humans ; Intracellular Signaling Peptides and Proteins ; physiology ; Molecular Sequence Data ; Phosphorylation ; Protein-Tyrosine Kinases ; physiology ; Proto-Oncogene Proteins c-fyn ; physiology ; Signal Transduction ; Syk Kinase ; Viral Envelope Proteins ; chemistry ; physiology

Molecular mechanisms underlying the effects of Fyn on cell morphology, pseudopodium movement, and cell migration were investigated. The Fyn gene was subcloned into pEGFP-N1 to produce pEGFP-N1-Fyn. Chinese hamster ovary (CHO) cells were transfected with pEGFP-N1-Fyn. The expression of Fyn mRNA and proteins was monitored by reverse transcription-PCR and Western blotting. Additionally, transfected cells were stained with 4',6-diamidino-2-phenylindole and a series of time-lapse images was taken. Sequences of the recombinant plasmids pMD18-T-Fyn and pEGFP-N1-Fyn were confirmed by sequence identification using National Center for Biotechnology Information in USA, and Fyn expression was detected by RT-PCR and Western blotting. The morphology of CHO cells transfected with the recombinant vector was significantly altered. Fyn expression induced filopodia and lamellipodia formation. Based on these results, we concluded that overexpression of mouse Fyn induces the formation of filopodia and lamellipodia in CHO cells, and promotes cell movement.
Animals ; Blotting, Western ; CHO Cells ; Cricetinae ; Cricetulus ; Genetic Vectors ; Green Fluorescent Proteins/genetics ; Mice ; Proto-Oncogene Proteins c-fyn/genetics/*metabolism ; Pseudopodia/*metabolism ; Reverse Transcriptase Polymerase Chain Reaction ; Time-Lapse Imaging ; Transfection

BACKGROUNDThe effect of chronic stress on cognitive functions has been one of the hot topics in neuroscience. But there has been much controversy over its mechanism. The aim of this study was to investigate the effects of chronic multiple stress on spatial learning and memory as well as the expression of Fyn, BDNF and TrkB in the hippocampus of rats.

METHODSAdult rats were randomly divided into control and chronic multiple stressed groups. Rats in the multiple stressed group were irregularly and alternatively exposed to situations of vertical revolution, sleep expropriation and restraint lasting for 6 weeks, 6 hours per day with night illumination for 6 weeks. Before and after the period of chronic multiple stresses, the performance of spatial learning and memory of all rats was measured using the Morris Water Maze (MWM). The expression of Fyn, BDNF and TrkB proteins in the hippocampus was assayed by Western blotting and immunohistochemical methods. The levels of Fyn and TrkB mRNAs in the hippocampus of rats were detected by RT-PCR technique.

RESULTSThe escape latency in the control group and the stressed group were 15.63 and 8.27 seconds respectively. The performance of spatial learning and memory of rats was increased in chronic multiple stressed group (P < 0.05). The levels of Fyn, BDNF and TrkB proteins in the stressed group were higher than those of the control group (P < 0.05). The results of immunoreactivity showed that Fyn was present in the CA3 region of the hippocampus and BDNF positive particles were distributed in the nuclei of CA1 and CA3 pyramidal cells as well as DG granular cells. Quantitative analysis indicated that level of Fyn mRNA was also upregulated in the hippocampus of the stressed group (P < 0.05).

CONCLUSIONSChronic multiple stress can enhance spatial learning and memory function of rats. The expression of Fyn, BDNF and TrkB proteins and the level of Fyn mRNA are increased in the stessed rat hippocampus. These suggest that Fyn and BDNF/TrkB signal transduction pathways may participate in the process of the enhanced learning and memory during chronic multiple stress.

Animals ; Blotting, Western ; Brain-Derived Neurotrophic Factor ; genetics ; metabolism ; Hippocampus ; metabolism ; Immunohistochemistry ; Learning ; physiology ; Male ; Memory ; physiology ; Proteins ; genetics ; metabolism ; Proto-Oncogene Proteins c-fyn ; genetics ; metabolism ; RNA, Messenger ; genetics ; metabolism ; Rats ; Rats, Wistar ; Receptor, trkB ; genetics ; metabolism ; Reverse Transcriptase Polymerase Chain Reaction ; Stress, Physiological ; physiopathology