New insights into cell division
As World AIDS Day 2008 approaches, a coalition of hundreds of HIV/AIDS medical care providers and advocates, representing dozens of organizations, today sent a letter to Dr. Margaret Chan, Director General of the World Health Organization (WHO), urging an end to harmful single-dose HIV/AIDS treatment as a recommended treatment for expectant mothers and infants worldwide.
Full Post: AIDS advocates tell WHO: Stop harmful single-dose treatment for expectant mothers and infants
Biologists have discovered a mechanism that is critical to cytokinesis — nature’s completion of mitosis, where a cell divides into two identical daughter cells.
The researchers have opened a new window on the assembly and activity of a ring of actin and myosin filaments that contract to pinch a cell at just the right time. They focused on key proteins whose roles drive signaling mechanisms that promote the production of both linear and branching microfilaments along the inside surface membrane of a dividing cell. By down-regulating the production of branched microfilaments at the right time, the membrane may be more malleable and better able to pinch inward and complete cytokinesis.
The findings– detailed in the Dec. 5 issue of the journal Science — come from basic research using Caenorhabditis elegans (roundworm) embryos. The discovery provides more basic insight than immediate biomedical application, but the implications could lead to a fine-tuning of anti-cancer drug therapies or to isolating new targets for drugs to stop cancerous cell division, said Bruce Bowerman, professor of biology in the University of Oregon’s Institute for Molecular Biology.
Bowerman and Karen Oegema of the Ludwig Institute for Cancer Research at the University of California, San Diego, were principal investigators of a seven-member team funded by the National Institutes of Health.
Scientists have theorized that the modulation of microfilament structure plays a role in healthy cell division. However, finding that such shape-shifting down-regulation specifically targets branched microfilaments assembly came as a surprise, Bowerman said.
C. elegans is used in many genetics research laboratories to discover basic requirements for the 20,000 genes that compose its genome; most of the genes are conserved in humans and carry out similar processes. Using these nematodes, Bowerman said, is allowing researchers to “find players inside that previously weren’t known to be involved in cytokinesis.”
The new research focused on enzymes targeted by the GAP domain of the protein CYK-4 that is part of a multi-protein complex called centralspindlin. This GAP domain functions as a GTPase activator, targeting protein switches called GTPases, which bind and hydrolyze guanosine triphosphate (GTP) to guanosine diphosphate (GDP). When GTPase is bound to GTP it acts as an on switch; when GTP is hydrolyzed to GDP, the switch is turned off.
The researchers found that deleting a GTPase called Rac could bypass the requirement for the GAP domain in CYK-4, Bowerman said. Because Rac GTPases promote branched microfilament assembly, this suggests that normally the CYK-4 GAP acts to down-regulate the production of branched microfilaments.
Previously CYK-4 had been thought to only down-regulate a different GTPase called RhoA, which promotes linear microfilament assembly. Thus these new results implicate the down-regulation of branched microfilaments at the cell cortex as a critical step in cell division.
“We have found a completely new way of thinking about how cells remodel their internal skeletons such that they undergo the shape changes needed to divide and produce daughter cells,” Bowerman said. “Some of these proteins already are targets of some cancer drugs. Now we have the opportunity to study and understand how certain proteins stabilize microfilaments within cells and inhibit cell division, and how other proteins act to modulate the stiffness of a cell’s membrane to allow them to undergo shape changes needed for cell division and proliferation.”
A Swedish research group, partly financed by NWO, has discovered a new mechanism for cell division in a microorganism found in extremely hot and acidic conditions. The results of the research offer insights into evolution, but also into the functioning of the human body. The research has been recently published in PNAS, the magazine
Full Post: Discovery of new mechanism for cell division
Garbage collectors are important for removing trash; without them waste accumulates and can quickly become a health hazard. Similarly, individual cells that make up such biological organisms as humans also have sophisticated methods for managing waste. For example, cells have developed complex systems for recycling, reusing and disposing of damaged, nonfunctional waste proteins. When such
Full Post: Researchers describe how cells recycle protein waste
Determining the mechanisms that shape biological membranes has long been a tricky business. Like a factory assembly line, eukaryotic cells are organized into membrane-bound, functional compartments called organelles. For instance, the nucleus is the repository of genetic information and houses the machinery that creates the messenger RNA transcripts, which direct the synthesis of new protein.
Full Post: Doing the math for membranes
CANCER RESEARCH UK scientists have linked cancer clues in faulty cells to provide a new route to cancer development, reveals a study published in Developmental Cell. Cancer is a disease caused by uncontrolled cell growth and division and understanding the complex molecular networks inside cells which regulate these processes is fundamental to understanding what goes
Full Post: Scientists establish completely new route to cancer development
The Stowers Institute’s Rong Li Lab has published findings that shed light on the ability of cells to adapt to disruptions to their basic division machineries - findings that may help explain how cancer cells elude the body’s natural defense mechanisms or chemotherapy treatment. The work was published in the November 26 issue of Cell
Full Post: Researchers provide new insight into adaptive ability of cells