We don't usually use a mace to drive a pin into a cork board. Living organisms, on the other hand, use destructive molecules called caspases - which perform destructive jobs such as killing unwanted cells - also for much more subtle purposes, such as "sculpting" cells, or transmitting signals between them.

The destructive power of caspases is so great, that if they were sold in a store, it would surely be written on them "keep away from children": they can cut into pieces and eliminate the molecular structures and proteins with which they come in contact. For example, the caspases are responsible for "cell suicide", i.e. the programmed cell death, called apoptosis." How can this deadly weapon perform more delicate tasks without causing damage or killing the cell?
In a study recently published in the scientific journal Developmental Cell, Dr. Eli Arma and the members of the research group he heads, in the Department of Molecular Genetics of the Weizmann Institute of Science, took an important step towards solving this mystery: they discovered how caspases carry out one of the delicate processes in the cell - the separation of sperm cells , to create compact and mobile cells, while removing the parts of the cell that are not necessary. This research helps to understand many processes in living cells that do not end in the elimination of the cell, and also sheds new light on apoptosis, which plays a central role in both normal processes in the cell and in disease states.
Dr. Arma and research student Yosef Kaplan, with the help of Liron Gibbs-Barr, Dr. Yossi Kalifa and Dr. Yael Feinstein-Rotkopf, discovered that when the caspases separate the sperm cells, their activity is limited by a large protein called dBruce. Protein It controls the activity of caspases and functions as a kind of "molecular stopper": normally the caspase cutter activated the structures in the cell like "Pac-Man", but when dBruce closes the "mouth" of Pac-Man, the caspase stops its killing activity. But it doesn't The whole story: the distribution of dBruce inside the cell is controlled by another molecule called Scotti.
Why is such a complicated, two-stage control mechanism necessary? Probably because Scotti, being a small molecule, is a more convenient switch than the bulky dBruce. In this way, Scotti can ensure that destructive molecules such as caspases are activated with maximum precision, at the right time and in the right amounts, to carry out their mission without killing the cell.
When the sperm cells - which first develop as a cocoon of cells - begin to separate from each other, they do so from the head towards the tail, like a horse's tail being separated into individual hairs with a comb. This separation is done through the caspases that break the cellular skeleton, but the one who controls the whole process is Scotti.
It can block a protein cluster (belonging to the ubiquitin system) that is needed for dBruce, the molecular stopper, to move inside the cell. In this way, Scotti controls the distribution of the dBruce throughout the cell, and makes sure that the amounts of "cork" gradually increase from the head of the sperm cell to its tail. In other words, it makes sure that caspase activity is lower in the tail. As a result, although the tails of sperm cells are the last to undergo separation, they are not exposed for too long to a lethal bath of caspases.
This research was done in fruit fly sperm cells, but the findings are relevant to mammals, including humans. In the future, they may help treat certain male fertility problems caused by defects in the formation of sperm cells. Also, they may have a much wider impact. Thus, among other things, the information obtained in these studies could help control apoptosis. In cancer, for example, we are interested in increasing apoptosis, because cancer cells manage to "escape" programmed cell death. And on the contrary, in degenerative diseases of the brain, such as Alzheimer's disease, cell death has been reduced.