As people around the world mark Earth Day (April 22) with activities that protect the planet, our cells are busy safeguarding their own environment.
To keep themselves neat, tidy and above all healthy, cells rely on a variety of recycling and trash removal systems. If it weren't for these systems, cells could look like microscopic junkyards—and worse, they might not function properly. Scientists funded by the National Institutes of Health are therefore working to understand the cell's janitorial services to find ways to combat malfunctions.
Office of Biological and Environmental Research of the U.S. Department of Energy Office of Science.
When proteins enter the proteasome, they're chopped into bits for re-use.
Garbage Disposal and Recycling Plant
One of the cell's trash processors is called the proteasome. It breaks down proteins, the building blocks and mini-machines that make up many cell parts. The barrel-shaped proteasome disassembles damaged or unwanted proteins, breaking them into bits that the cell can re-use to make new proteins. In this way, the proteasome is just as much a recycling plant as it is a garbage disposal.
How does the cell know which proteins to keep and which to trash? The 2004 Nobel Prize in chemistry went to three scientists for answering that question. They found that the cell labels its refuse with a tiny protein tag called ubiquitin. Once a protein has the ubiquitin label, the proteasome can grab it, put it inside the barrel, break it down and release the pieces.
Because diseases like Alzheimer's involve the accumulation of excess proteins, researchers are trying to develop medicines to help the proteasome out. They hope such a treatment would keep brain cells clean and healthy.
Scientists are also interested in designing medicines that turn off the proteasome. Cancer cells, for instance, make a lot of abnormal proteins that their proteasomes have to remove. A proteasome-clogging medicine could prevent cancer cells from recycling their own garbage, leaving them without reusable resources for survival and growth. This is the approach behind the proteasome inhibitor drug bortezomib, which is used for the blood cancer multiple myeloma.
Proteins aren't the only type of cellular waste. Cells also have to recycle compartments called organelles when they become old and worn out. For this task, they rely on an organelle called the lysosome, which works like a cellular stomach. Containing acid and several types of digestive enzymes, lysosomes digest unwanted organelles in a process termed autophagy, from the Greek words for "self" and "eat." The multipurpose lysosome also processes proteins, bacteria and other "food" the cell has engulfed.
An inability to make one of the lysosomal enzymes can lead to a rare, life-threatening sickness called a lysosomal storage disease. There are more than 40 different lysosomal storage diseases, depending on the kind of trash that's unprocessed. These diseases can affect many organs, including the brain, heart and bones.
Lysosomes also gobble up viruses, an activity important to fighting infections. A drug that activates lysosomes protects mice from diseases like West Nile virus. It's possible that the same or similar medications might treat diseases in which cellular trash piles up, including Alzheimer's and other diseases of aging.
While cells mainly use proteasomes and lysosomes, they have a couple of other options for trash disposal.
Sometimes they simply hang onto their trash, performing the cellular equivalent of sweeping it under the rug. Scientists propose that the cell may pile all the unwanted proteins together in a glob called an aggregate to keep them from gumming up normal cellular machinery.
For example, a protein called islet amyloid polypeptide builds up in aggregates in the pancreas of people with type 2 diabetes. Other proteins form aggregates in certain brain diseases. Scientists are still trying to understand what these trash piles do and whether they're helpful or harmful.
If the garbage can't be digested by lysosomes, the cell can sometimes spit it out in a process called exocytosis. Once outside the cell, the trash may encounter enzymes that can take it apart, or it may simply form a garbage heap called a plaque. Unfortunately, these plaques outside the cell may be harmful, too.
The cell also has ways to toss out some poisons that get inside. This means that cancer cells may pump out cancer drugs that are meant to destroy them, and bacteria may do the same with antibiotics. Scientists are studying how these pumps work, looking for ways to keep the medicines inside where they can do their job.
Further study of the many ways cells take out the trash could lead to new approaches for keeping them healthy and preventing or treating disease.
Inside the Cell Booklet http://publications.nigms.nih.gov/insidethecell/
Shelly Pollard |
How Invasive Plants Influence an Ecosystem
28.07.2016 | Albert-Ludwigs-Universität Freiburg im Breisgau
Perseus translates proteomics data
27.07.2016 | Max-Planck-Institut für Biochemie
Transparent electronics devices are present in today’s thin film displays, solar cells, and touchscreens. The future will bring flexible versions of such devices. Their production requires printable materials that are transparent and remain highly conductive even when deformed. Researchers at INM – Leibniz Institute for New Materials have combined a new self-assembling nano ink with an imprint process to create flexible conductive grids with a resolution below one micrometer.
To print the grids, an ink of gold nanowires is applied to a substrate. A structured stamp is pressed on the substrate and forces the ink into a pattern. “The...
A new Fraunhofer MEVIS method conveys medical interrelationships quickly and intuitively with innovative visualization technology
On the monitor, a brain spins slowly and can be examined from every angle. Suddenly, some sections start glowing, first on the side and then the entire back of...
Researchers at the U.S. Department of Energy's (DOE) Ames Laboratory have discovered an unusual property of purple bronze that may point to new ways to achieve high temperature superconductivity.
While studying purple bronze, a molybdenum oxide, researchers discovered an unconventional charge density wave on its surface.
Munich Physicists have developed a novel electron microscope that can visualize electromagnetic fields oscillating at frequencies of billions of cycles per second.
Temporally varying electromagnetic fields are the driving force behind the whole of electronics. Their polarities can change at mind-bogglingly fast rates, and...
Breakup of continents with two speed: Continents initially stretch very slowly along the future splitting zone, but then move apart very quickly before the onset of rupture. The final speed can be up to 20 times faster than in the first, slow extension phase.phases
Present-day continents were shaped hundreds of millions of years ago as the supercontinent Pangaea broke apart. Derived from Pangaea’s main fragments Gondwana...
15.07.2016 | Event News
15.07.2016 | Event News
11.07.2016 | Event News
28.07.2016 | Information Technology
28.07.2016 | Materials Sciences
28.07.2016 | Earth Sciences