Back to David's theory of evolution: garbage systems (Evolution)

by David Turell @, Monday, June 29, 2020, 21:33 (88 days ago) @ David Turell

They are part of the corrective mechanisms to keep cells functional:

https://phys.org/news/2020-06-osmotic-stress-cellular-disposal.html

"Cellular waste disposal, where autophagy and lysosomes interact, performs elementary functions, such as degrading damaged protein molecules, which impair cellular function, and reintroducing the resulting building blocks such as amino acids into the metabolic system.

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"Researchers...have now discovered a previously unknown mechanism: osmotic stress, i.e. a change in water and ionic balance, triggers a response within hours, resulting in the increased formation and activity of autophagosomes and lysosomes.

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"Our cells are occasionally in need of a "spring clean" so that incorrectly folded protein molecules or damaged cell organelles can be removed, preventing the aggregation of protein molecules. The mechanisms responsible for this removal are so-called "autophagy" and the closely related lysosomal system, the discovery of which earned the Nobel Prize for Medicine in 2016.

"Quite a number of studies suggest that autophagy and lysosomes play a central role in aging and in neurodegenerative diseases. It is also generally agreed that fasting or food deprivation can kickstart this cellular degradation and recycling process. Other than that, little is known about how cells and organs control the quality of their protein molecules, and which environmental influences give the decisive signal to start cleaning up.

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"'When dehydration occurs, we suddenly see more lysosomes in the cells, i.e. more organelles where aggregated protein molecules are degraded," explained co-last author PD Dr. Tanja Maritzen. "It's a clever adaptation because cellular water loss simultaneously fosters the aggregation of proteins. These aggregates must be removed quickly to ensure the continued function of cells, and this works better when cells have more lysosomes."

"The researchers were able to observe what happens at the molecular level in dehydrated cells using astrocytes, star-shaped cells in the brain that assist the work of our nerve cells: in the event of dehydration, the ion transporter NHE7 translocates from the cell's interior, where it is normally positioned, to the cell's limiting plasma membrane that shields the cell from the outside. This leads to an influx of sodium ions into the cell, indirectly increasing the level of calcium—a key messenger—in the cytosol. The elevated level of calcium in turn activates a transcription factor called TFEB, which finally switches on autophagy and lysosomal genes. In other words, the system is initiated by the ion transporter NHE7, triggered by osmotic stress.

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"...it is not yet clear how osmotic stress affects the translocation of NHE7 to the cell surface. It is also not known whether the entire degradation system is initiated or whether just individual genes are switched on, or which specific responses to osmotic stress are needed to activate the lysosomal system. Nor is it known which other stimuli may be triggered by this physiological process."

Comment: It is clear the designer of the biochemistry of life recognized there had to be a mechanism for the clearance of garbage as it developed. This had to be present when life started or it would have collapsed upon itself in piled up debris. dhw would prefer it if God arranged a biological system that had no garbage. Can't done, based on our studies of life's processes. We are still at theodicy, the assumption that God does not keep everything perfect and He should when He creates.


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