The baculovirus gp64 envelope glycoprotein is a major component of the envelope of the budded virus (BV) and is involved in BV entry into the host cell by endocytosis. To determine whether gp64 alone was sufficient to mediate membrane fusion, the Orgyia pseudotsugata multicapsid nuclear polyhedrosis virus gp64 protein was transiently expressed in uninfected insect cells. Cells expressing the baculovirus gp64 protein were examined for membrane fusion activity by using a syncytium formation assay under various conditions of exposure to low pH. Cells expressing the gp64 protein mediated membrane fusion and syncytium formation in a pH-dependent manner. A pH of 5.5 or lower was required to induce membrane fusion. In addition, exposure of gp64-expressing cells to low pH for as little as 5 s was sufficient to induce gp64-mediated syncytium formation. These studies provide direct evidence that gp64 is a pH-dependent membrane fusion protein and suggest that gp64 is the protein responsible for fusion of the virion envelope with the endosome membrane during BV entry into the host cell by endocytosis.

Baculovirus gp64 envelope glycoprotein is sufficient to mediate pH-dependent membrane fusion.

Mechanisms and kinetics of liposome-cell interactions

We have characterized the parameters describing the total association (uptake) of liposomes with murine macrophage-like cell line J774 cells and human peripheral blood monocytes at 4 degrees C and at 37 degrees C with or without inhibitors of endocytosis. The uptake of neutral liposomes composed of phosphatidylcholine (PC)/cholesterol (Chol) (2:1 mole ratio) is about 10-fold lower than that of negatively charged liposomes composed of phosphatidylserine (PS)/PC/Chol (1:1:1). However, the rate of uptake of PC/Chol liposomes at 37 degrees C is still 10-fold higher than that by fluid-phase pinocytosis. The uptake of liposomes, which is mediated by high-affinity binding to the cell surface binding sites and subsequent endocytosis, could be simulated and predicted by model calculations employing mass action kinetics. The number of binding sites, affinity constants of binding at 37 degrees C and 4 degrees C, on- and off-rate constants of binding, and endocytic rate constants for both types of liposomes were determined. The number of binding sites and the binding constants for PS/PC/Chol liposomes binding to J774 cells is severalfold to an order of magnitude higher than that for PC/Chol liposomes, but the rate constants at which they are endocytosed following binding to the cells are similar for both liposome types. The binding of liposomes, especially PS/PC/Chol, to J774 cells and monocytes is greatly enhanced by adherence of cells to plastic substratum and is also increased by maturation/differentiation in the case of monocytes. Our quantitative analysis indicates that the binding and endocytosis of liposomes, especially PS-containing liposomes, is mediated by binding sites that have strong affinity, comparable to or about an order of magnitude smaller than other known particle-cell interactions with specific receptors such as virus and lipoproteins binding to cells.

Quantitative analysis of liposome-cell interactions in vitro: Rate constants of binding and endocytosis with suspension and adherent J774 cells and human monocytes

Conformational changes in Sindbis virions resulting from exposure to low pH and interactions with cells suggest that cell penetration may occur at the cell surface in the absence of membrane fusion

https://www.cell.com/biophysj/pdf/S0006-3495(96)79822-3.pdf

Reversible surface aggregation in pore formation by pardaxin

The kinetics of fusion of influenza virus (A/PR/8/34) with human promyelocytic leukaemia (HL-60), human T lymphocytic leukaemia (CEM) and murine lymphoma (S49) cells were investigated. Fusion was demonstrated by electron microscopy, and monitored by fluorescence dequenching of octadecylrhodamine incorporated in the virus membrane. Rapid fusion was induced upon mild acidification of the medium. At pH 5, all virus particles were capable of fusing with the cells. The initial rate and the extent of fusion were maximal between pH 4.9 and 5.2 and declined sharply below and above this range. The rate constants of adhesion of influenza virus to cells or erythrocyte ghosts were large, indicating a diffusion-controlled process. The rate constants of fusion of the virus with cells were smaller than those found previously for fusion with various liposomes. Although preincubation of the virus at acidic pH in the absence of target membranes almost completely inactivated the virus in its ability to fuse with erythrocyte ghosts, it reduced the extent of fusion with cultured cells by only 20 to 40%. Kinetic analysis of fusion revealed a mode of inactivation of the virus bound to erythrocyte ghosts or suspension cells, below pH 5.4, different from that of the virus preincubated at low pH without target membranes.

/pdf/fusion-activity-and-inactivation-of-influenza-virus-kinetics-4ulg8vpi25.pdf

Fusion activity and inactivation of influenza virus: kinetics of low pH-induced fusion with cultured cells.

Handle everyday research tasks with reliable, citation-backed results

Your personal Research Agent to handle research tasks with citation-backed results

Popular Tasks used by Researchers

How can I help with your research?

Meet SciSpace

Get more enhanced response by uploading the PDFs you want me to reference.

No relevant PDFs in your library

SciSpace is the AI research assistant for academics. Run systematic literature reviews on 280M+ papers, and write papers with cited sources. Trusted by 1M+ students, PhDs & researchers.

SciSpace | AI for Research

Analyze PDFs

Code & Manuscripts

Funding & Grants

Literature & Patents

Medical & Clinical Data

Systematic Review

Visualize & Present

Web & Data

Build a Google Scholar-like website for your research.

Build a website

Create charts and images for your research

Create a Chart

Write a paper for submission to a journal

Draft a manuscript

Patent Search

Design eye-catching scientific posters in minutes.

Scientific Poster Generation

Systematic Literature Review

One task is running at the moment. Your messages will be shown right after.

Drag and drop or click here to browse

Loved by <highlight>1 million+</highlight> researchers

Extract a list of specific topics and their sources from unstructured text

Topics

Compare and analyze relevant papers that matches with your search

Papers

Get insights from PDFs and bookmarked papers from your library

My library

Recent searches

Try searching for:

Catch AI-generated content in scholarly and non-scholarly content

{ai} Detector

Ai Writer

Get PDF Summaries, highlighted text explanations 

Chat with PDF

Effortlessly create in-text citations and bibliographies in APA and 2,500 other formats

Citation generator

Get explanations, summaries, and answers on academic papers

Ease up your research workflow with {scispace}'s cohort of exciting AI tools

Elevate your academic writing skills and convey your ideas the way you want

Paraphraser

Explore our range of reading and writing tools

Your file is being prepared and should be ready in a few minutes. If it's a large file, it might take a bit longer. You can close this window, and we'll email you the file when it's done.

You have reached a maximum limit of <strong>{limit}</strong> columns in the table. Remove at least <strong>1</strong> column to add or create another one.

D. Alford

Author Tools

Chat about Author

Papers

Fusion activity and inactivation of influenza virus: kinetics of low pH-induced fusion with cultured cells.