Featured Research

from universities, journals, and other organizations

Virology: Some viruses use fats to penetrate a cell

Date:
February 8, 2010
Source:
ETH Zurich
Summary:
SV40 viruses use an amazing means of communication, in order to be able to penetrate into a cell: fats, whose structure must fit like a key in a lock.

The icosahedric SV40 binds to glycolipids, a class of cell membrane fats. (Figure not to scale)
Credit: Image courtesy of ETH Zurich

SV40 viruses use an amazing means of communication, in order to be able to penetrate into a cell: fats, whose structure must fit like a key in a lock.

Just like a ball, driven into the goal, causing the net to bulge out and wrap itself closely around the leather: This is how it appears when the Simian Virus 40 (SV40) penetrates into a cell. The virus docks onto the cell membrane, which in turn invaginates deeply, wraps itself tightly around the intruder and buds into a vesicle that is finally pinched off inside the cell.

Suitable Trojans required

Until recently, scientists were unable to explain how this dramatic rearrangement of the cell membrane took place in order to make it possible for the virus to penetrate, since only few proteins seem to be involved in this process. A new work, which has just appeared in Nature Cell Biology, now throws new light on the mechanism by which the SV40 outwits its host: it exploits the components of the cell membrane itself, fats.

If a virus wants to reproduce itself, the same question generally arises: How does it get into a cell in order to use the latter's reproductive mechanism for its own purposes? After all, although viruses carry with them a short piece of genetic information depending upon their type, they need to penetrate into the cell and its nucleus in order to propagate their genome. There, the cells own replication machinery is reprogrammed to produce new viruses, which finally abandon the cell and infect further cells.

Fats as a Velcro fastener

SV40 has now developed a unique strategy. Instead of binding to a protein receptor in the plasma membrane and entering vesicles created by an apparatus around the protein molecule clathrin, this polyomavirus attaches itself to lipids. It does however not bind to one receptor, but many lipid molecules, in a similar way to a Velcro fastener. The individual connections are weak, but many connections taken together are strong. As soon as the virus has connected itself to many fats, the plasma membrane of the cell changes dramatically: It undergoes deep invagination and, in the course of time, completely surrounds the virus and finally forms a vesicle, which is pinched off inside the cell.

Interestingly the many connections are not only important for virus binding, but also for this membrane deformation process. The researchers could show that different molecules binding to the same fat cannot deform the membranes. At least five fat connections were required for membrane deformation. The membrane is then organized so closely around the virus that hardly any space remains between its surface and the virus. The virus in this way optimizes the number of connections with the membrane and can exert a strong force on the membrane sufficient to deform it without the help of cellular proteins.

Short chains do not bind

In addition, the correct fats must be present on the surface of the virus. The carbon chains forming part of the fat must be of the correct length. If they are too short, then the membrane does not invaginate. This has been demonstrated by experiments with structurally altered fats.

"It surprised us that there is a relationship between structure and function even with fats," observed Helge Ewers, ETH Group-Leader, who signs as primary author of the paper. With proteins, such key/lock principles are common. "With this work we have proven that it can also be the same for fats," says the former graduate student of Ari Helenius, Professor of Biochemistry.

Widely distributed mechanism

In co-operation with the Curie Institute in France the ETH researchers were able to show that SV40 is not the only pathogen, which gains entry to cells via multi-lipid connections. This route is also taken by bacterial toxins, such as, for instance, the cholera toxin or mouse polyomavirus. It thus seems to be a widespread mechanism.

It is not yet possible, however, to use this knowledge therapeutically. Antiviral medicines continue to eliminate the infected cells. Finding active substances, which block the viral fat connection, is considered by Ewers and Helenius to be a difficult task.

SV40

SV40 naturally infects Asian apes, such as macaques and rhesus monkeys. It can also be passed on to humans. In the '60s it was discovered in cultures of kidney cells from rhesus monkeys. The cells were used for the production of vaccines against polio, the childhood paralysis. During the inoculation from 1955 to 1963 several million humans were probably infected with SV40. Like other polyomaviruses, SV40 can cause tumours under certain conditions. However, in most cases the infection remains symptom-free. In humans no direct connections between an SV40-infection and the emergence of cancer could be proven. Oncogenes of this virus, however, play a role in the emergence of cancer cells from human cells in cell culture.


Story Source:

The above story is based on materials provided by ETH Zurich. Note: Materials may be edited for content and length.


Journal Reference:

  1. Ewers H et al. GM1 structure determines SV40-induced diaphragm invagination and infection. Nature Cell Biology, 20 December 2009 DOI: 10.1038/ncb1999

Cite This Page:

ETH Zurich. "Virology: Some viruses use fats to penetrate a cell." ScienceDaily. ScienceDaily, 8 February 2010. <www.sciencedaily.com/releases/2010/01/100129105934.htm>.
ETH Zurich. (2010, February 8). Virology: Some viruses use fats to penetrate a cell. ScienceDaily. Retrieved April 25, 2014 from www.sciencedaily.com/releases/2010/01/100129105934.htm
ETH Zurich. "Virology: Some viruses use fats to penetrate a cell." ScienceDaily. www.sciencedaily.com/releases/2010/01/100129105934.htm (accessed April 25, 2014).

Share This



More Plants & Animals News

Friday, April 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Deadly Fungus Killing Bats, Spreading in US

Deadly Fungus Killing Bats, Spreading in US

AP (Apr. 24, 2014) A disease that has killed more than six million cave-dwelling bats in the United States is on the move and wildlife biologists are worried. White Nose Syndrome, discovered in New York in 2006, has now spread to 25 states. (April 24) Video provided by AP
Powered by NewsLook.com
Blood From World's Oldest Woman Suggests Life Limit

Blood From World's Oldest Woman Suggests Life Limit

Newsy (Apr. 24, 2014) Scientists say for the extremely elderly, their stem cells might reach a state of exhaustion. This could limit one's life span. Video provided by Newsy
Powered by NewsLook.com
Raw: Kangaroo Rescued from Swimming Pool

Raw: Kangaroo Rescued from Swimming Pool

AP (Apr. 24, 2014) A kangaroo was saved from drowning in a backyard suburban swimming pool in Australia's Victoria state on Thursday. Australian broadcaster Channel 7 showed footage of the kangaroo struggling to get out of the pool. (April 24) Video provided by AP
Powered by NewsLook.com
Could Marijuana Use Lead To Serious Heart Problems?

Could Marijuana Use Lead To Serious Heart Problems?

Newsy (Apr. 24, 2014) A new study says marijuana use could lead to serious heart-related complications. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins