Biological complexity: homeostasis and cell function (Introduction)

by David Turell , Tuesday, October 16, 2018, 19:14 (2011 days ago) @ David Turell
edited by David Turell, Tuesday, October 16, 2018, 19:22

Cells are busy factories under tight controls:

https://www.sciencedaily.com/releases/2018/10/181015084553.htm

"Proteins in a cell are like cars in a city. The cell has different means to fix broken proteins, sometimes choosing less obvious paths.

"The steps cells take in response to challenges are more complex than previously thought, finds new research published in the journal eLIFE.

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"Surprisingly, cells often take an approach that seems quite inefficient," explains Christine Vogel, an associate professor at New York University's Department of Biology and the study's lead author.

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Each cell in the human body produces as many as 1.5 million protein molecules every minute -- and folding the proteins into their right shape is a vital and enormous task. If too many proteins misfold and accumulate, cellular health is in immediate danger and may eventually cause the cell to die. (my bold)

"For that reason, the "cellular stress response" is central to many human diseases. Misfolded proteins occur in rapidly dividing cancer cells that produce many more protein molecules than normal -- or in virus infected cells where the virus hijacks the host's protein manufacturing machinery.

"Therefore, cells develop multiple mechanisms to fight the accumulation of misfolded proteins, to stop the synthesis of proteins, and refold existing ones properly.

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What the scientists discovered was contrary to their expectations."The normal process to make proteins from genes consists of two major steps, called transcription and translation," explains Vogel. "If you have misfolded proteins accumulating in the cell, you would think that the first and easiest response should be to shut down these two steps in order to avoid producing even more proteins. And indeed, we observe many genes for which translation stops in response to misfolded molecules in the cell."

"However, the researchers also found a surprising number of very different responses. For example, many genes did not participate in the global translation shutdown, but rather increased the second synthesis step, producing even more protein molecules from these genes.

"Others did decrease their translation according to the standard model, but, conversely, increased the first step -- transcription -- rendering a seemingly uneconomical process.
Why the easiest route is often not taken is still subject to speculation, the researchers note.

"'The cells are much smarter than just turning everything off under stress, and we have some ideas as to why," Vogel says. "For some genes, the cells want to be particularly fast in ramping up synthesis when misfolded proteins occur -- to support the refolding machinery, for example. To save time, the cell then always conducts the first step for these genes in a somewhat wasteful manner, so that only the second step is left to do when the proteins are needed. For others, the cell activates the genes' protein production halfway through 'just in case' they are needed -- and therefore prepares for all eventualities.'"

Comment: We are looking at cells through human eyes and only partially, at this point, understand fully why cells are acting in ways like they are. Remember the human retina: it looks like it is designed wrong, but research shows that strange design gives us special sight properties we might otherwise not have. At some point in research we will understand cells actions as well designed and reasonable. Note my bold which shows just how busy cells are. There must be tight feedback controls. Not by chance.