Comprehensive coverage

No organ is an island

How is it possible to locate the tiny connection points between the cell organelles?

Microscope image of yeast cells. Mitochondrial organelles (indicated in red) are attached to peroxisomes (in light blue) by tiny "ribbons" (in green). Illustration: Weizmann Institute
Microscope image of yeast cells. Mitochondrial organelles (indicated in red) are connected to peroxisomes (in light blue) by tiny "bands" (in green). Illustration: Weizmann Institute

No man is an island, he is all of his own accord; "Every man is a piece of land, a part of a great land," wrote the English poet John Dunn in the 17th century (Hebrew translation: Rami Ditzni). Similarly, the organelles - the biological structures that make up the living cell - are not separate islands sailing in the cell fluid, each one for himself. With the help of a unique method, Weizmann Institute of Science scientists have revealed new connection and launching points between the cell organelles which are connected to each other by means of tiny "bands". The results of the study were published recently In the scientific journal Nature Communications.

The organelles are distinct parts of the cell, each of them is surrounded by a membrane, and each one has a unique role: the nucleus contains our genetic material, the mitochondria convert energy, the intraplasmic reticulum sorts proteins intended for secretion, the lysosomes break down proteins, and so on. In a previous study, Prof. Maya Shuldiner, from the Department of Molecular Genetics, discovered several points of connection between organelles. However, due to their small dimensions - only a few tens of nanometers long - the connection points are not visible in normal microscope images, and therefore it is difficult to locate all the points that are assumed to exist.

Prof. Shuldiner, together with faculty scientist Dr. Einat Salzkaber, and research student Nadav Shai, decided to take a new approach to locating the connection points, using a fluorescent protein. The scientists coated one of the organelles in the cell with half of the protein, and connected the other half to other organelles in the cell. When two organelle membranes came into contact with each other, the two halves formed one complete protein - and a glow, which can be seen under a normal fluorescence microscope. Since the yeast cells are grown in Prof. Shuldiner's laboratory in thousands of "barria", and are automatically scanned under a microscope, this method made it possible not only to locate points of contact between several different organelles, but also to scan all the proteins in the yeast in an attempt to locate potential connecting "bands".

"If until a few years ago we thought that organelles floated in the 'soup' of the cell, while collecting messages floating in this 'soup', now we know that each organelle has its own position in the cell, and this position is determined by a network of 'bands' which also serves A direct means of passing materials through physical contact"

In this way, the researchers were able to map the physical connections between several main organs, and find four completely new connection points. "We found that all the organelles we tagged are able to maintain connections with all the others," says Shay. "The bands that connect the organelles organize the cell and assign a location to the various organelles. For example, two organelles that need to work closely together will naturally be tied together in a certain area of ​​the cell. Furthermore, the connection using the ligaments appears to be an effective way to transfer from organ to organ materials or messages that could be harmful if they reach the wrong place."

Later, the research team decided to examine a specific connection point, the one that links the peroxisome organelle to the mitochondria. The peroxisome breaks down fats, both for using them as raw materials for energy conversion in the mitochondria and for removing toxic fats from the cell. For example, the lipids that make up the myelin coating on nerve cells can be toxic if there are large amounts of them. Thus, if the peroxisome does not function properly in the cells that produce the protective layer, this may cause severe nerve damage, and often even the death of the patient. In general, "peroxisomal diseases" - such as X-ALD described in the movie "Lorenzo's Fat" - are genetic diseases that have devastating consequences.

Most of the broken down fats are transported directly to the mitochondria. Hence, the peroxisome needs an efficient way to connect to the cell's energy converter. The research group was able to identify two genes that produce the "bands" that connect the mitochondria to the peroxisome. With the help of a team of experts in peroxisomal diseases from the Medical Center of the University of Amsterdam, the Netherlands, the group identified the function of the connection point: the transfer of lipid breakdown products to the mitochondria for their use. From the research, it emerged, therefore, that certain peroxisomal diseases are actually connection disorders, that is, a condition in which the peroxisome is unable to transport the products of fat breakdown to their destination.

"When it comes to basic functions," explains Dr. Salzkaber, "yeast cells are almost identical to our cells. So it is likely that the connections and extensions that we saw in the Shemer cells can also be found here. Another advantage is that yeast is very easy to grow, they have fewer genes, and there is a lot of extensive research in relation to them. After we identify the role of proteins in yeast cells, we know where to look for them in human cells." Shay adds: "Many laboratories have already adopted our method to discover new intracellular connections. Since the method is based on tools found in most laboratories, and in light of the fact that it is also valid for human cells, we believe that it will be very useful for genetics and cell biology researchers."

"The discovery of binding sites within the cell in recent years has opened our eyes," says Dr. Salzkaber. "If until a few years ago we thought that organelles floated in the 'soup' of the cell, while collecting messages floating in this 'soup', now we know that each organelle has its own position in the cell, and this position is determined by a network of 'bands' which also serves A direct means of passing materials through physical contact". Prof. Shuldiner adds: "Understanding the organization of cell organelles and their interrelationships has revolutionized the field of cell biology. We believe that the new method we developed for revealing connection points between organs will lead scientists in the coming years to new and interesting paths."

More of the topic in Hayadan:

One response

  1. Are the "bands" microtubulin? If not, what are they made of?
    The latter move closer and further apart with the help of the instability (disconnection) of the fibers?

Leave a Reply

Email will not be published. Required fields are marked *

This site uses Akismat to prevent spam messages. Click here to learn how your response data is processed.