Biological complexity: sorting chemicals in the cell (Introduction)

by David Turell , Saturday, November 16, 2019, 21:42 (1619 days ago) @ David Turell

A newly found complex mechanism:

https://www.sciencedaily.com/releases/2019/11/191115074402.htm

"A recent study by a group of scientists has revealed that a different mechanism is responsible for the formation and maintenance of the cell organelle called endosome that sorts and distributes substances entering a cell. Contrary to current knowledge in the field, the scientists show that the functioning of the Golgi is crucial for this organelle's upkeep.

"The cells in our body are workshops that continuously operate to produce and process substances to keep us going. When a substance enters a cell for processing, it is surrounded by a portion of the cell's outer membrane to form a sac. The sac then buds off into the cell and becomes a vesicle containing the substance. This ingestion of substances by the cell is called endocytosis. The vesicle is then quickly merged with an endosome, an organelle also frequently referred to as a 'sorting station'. From the endosome, the substance is either recycled back to the cell membrane (for exiting the cell) or forwarded to a lysosome -- a cell organelle containing enzymes for the breakdown of substances -- for degradation. The substances entering a cell -- and thereby an endosome -- could be nutrients or signal molecules for processing, or even pathogenic viruses which can cause disease. It is therefore extremely important to fully understand the molecular basis of how endosomes are formed and maintained.

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"...in a recent study published in Communications Biology, a group of scientists from Japan and Austria, led by Prof Jiro Toshima from the Tokyo University of Science, claims that vesicles transported out of the Golgi -- another crucial cell organelle -- and not those from the cell membrane are more important for the formation and maintenance of endosomes. "We used our research to show that endocytic vesicle internalization is not essential, but that vesicle transport from the trans-Golgi network [TGN; the Golgi] is crucial," the team of scientists says.

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"Prof Toshima and group saw that certain proteins, which are either resident in the Golgi or recruited to it, are transported from the Golgi to the endosomes where they activate Rab5 and spark the formation of endosomes. Deleting or deactivating the genes crucial to the transport of these proteins from the Golgi ultimately affects endosome formation.

"Thus, considering all of these results together, it appears that endocytosis is not necessary for endosome formation and maintenance, but vesicle transport form the Golgi is. "Our results provide a different view of endosome formation and identify the TGN as a critical location for optimal maintenance and functioning of endosomes," Prof Toshima says.

"Given that endosomes are essential to the functioning of the cell and, by extension, the organism, understanding the mechanism of its upkeep is important. The results of this compelling study reveal but a fraction of this mechanism and much remains to be discovered. Even so, this advancement in the knowledge of one of the core pathways by which cells process substances in the body can lead to enhanced comprehension of the molecular basis of diseases that involve defective endosomes, thereby leading to better treatments for such diseases."

Comment: More cellular complexity. How much exquisite complexity has to be shown before everyone realizes a designer is required