Defensins Bar Viruses from Cells
By Biotechdaily staff writers
Posted on 17 Oct 2005
Researchers have found that the defensin class of proteins protects cells from viral infection by cross-linking cell surface glycoproteins, which prevents the virus particles from binding to and fusing with the cell membrane.Posted on 17 Oct 2005
Defensins comprise a family of small (30-35 residue) cysteine-rich cationic proteins primarily found in vertebrate phagocytes. Investigators at the [U.S] National Institutes of Health (Bethesda, MD, USA; www.nih.gov) worked with epithelial cells from the inner surface of the lungs to study how defensins prevent viruses from entering the cells.
They reported in the October 2005 issue of Nature Immunology that defensins work in a lectin-like fashion to cross-link and immobilize glycoproteins in the cell membrane. Viruses usually cause the glycoproteins to clump together exposing areas of the membrane surface to which they can bind, fuse, and enter the cell. Defensin cross-linking locks the virus out.
"Defensins do not kill the virus, they just prevent it from entering the cell,” said senior author Dr. Leonid V. Chernomordik, head of the section on membrane biology in the laboratory of cellular and molecular biophysics at NIH. "Viruses that are not allowed to enter the cells can then be destroyed by the cells of the immune system.”
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