Remarkable Cell Processes That Keep You Alive
Within the factories of molecular machines that run living cells, including those in the human body, processes occur non-stop that are designed to meet every contingency. Here are just a few examples.
Parking garage: Most of us have driven round and round in those multi-level parking garages looking for a spot. We have something like that in our cells, too: helical ramps within an organelle called the endoplasmic reticulum, where proteins are given final assembly and checkups before being put into operation. Science Daily has a diagram of the structure. Nature News described how it works the same way as a parking garage, allowing “for dense, adjustable packing of material in the cell, boosting the surface available for protein production within a small volume.”
Brain tune-up: To perform in concert, neurons in the brain occasionally need to tune their signals, like orchestra players tune their instruments. Science Daily described how they do it: NIH findings show that “brief bursts of chemical energy coming from rapidly moving power plants, called mitochondria, may tune brain cell communication.” About a third of mitochondria move along tracks in the axon. Their presence seems to provide a reference tone, like a tuning fork, for signals: “the presence of stationary power plants at synapses controls the stability of the nerve signal strength.”
Cell division conductors: Speaking of orchestra players, there wouldn’t be music without an orchestrator. Centrioles are tiny bundles of microtubules located at the foci of mitotic spindles, the structures that pull chromosomes apart during cell division (mitosis). They are always found in pairs perpendicular to each other. PhysOrg discussed their “manifold functions in the cell,” including “orchestrators of cell division,” a “tightly regulated process.” European biochemists investigated the mysterious “pericentriolar material” (PCM) that binds them into the “centrosome” where, in a still mysterious way, they winch the chromosomes into the daughter cells. “Our results show that the PCM still harbors many surprises,” one of the researchers said.
Damage repair team spirit: A paper in PNAS describes what happens when lesions form on DNA strands, triggering “excision repair” processes. The title describes what happens: “Homologous recombination rescues ssDNA gaps generated by nucleotide excision repair and reduced translesion DNA synthesis…” The study, performed on yeast cells, describes cooperation between translesion DNA synthesis (TLS), single-stranded DNA repair (ssDNA), and homologous recombination, which rebuilds a damaged strand from the intact strand. “These findings suggest that ssDNA that might originate during the repair of closely opposed lesions or of ssDNA-containing lesions or from uncoupled replication may drive recombination directly in various species, including humans.”
Checkpoint charlies: A technical paper in Science Magazine described the interactions of multiple players that use checkpoints to ensure genomic integrity. The teams include proteins, small interfering RNAs, and multi-part enzymes. These players are all involved in “DNA Replication Origin Firing in Human Cells,” i.e., making sure that the all-important task of replicating the genome begins at the right spot. Here’s a taste of the technical details: “We propose that MTBP acts with Treslin/TICRR to integrate signals from cell cycle and DNA damage response pathways to control the initiation of DNA replication in human cells.”
Master regulator: A paper in Nature uncovers more findings about mTOR kinase, which it calls “a master regulator of cell growth.” The opening paragraph describes why this enzyme is important:
Whether or not a cell grows is decided by a remarkable protein kinase enzyme called mTOR. As part of two complexes, mTORC1 and mTORC2, mTOR integrates and interprets all sorts of factors that influence cell growth — including nutrients, stressors and the outputs of signal-transduction networks — by targeting a multitude of substrates that drive processes such as protein translation, metabolism and cell division. Research into mTOR-mediated signalling has taken on added urgency since it was discovered that most cancers contain mutations that inappropriately activate this protein.
The newly-uncovered structure of mTOR, made up of 1,500 amino acids, shows that it has a “gatekeeper mechanism that controls substrate access to the active site.”
You’re the boss: As a functioning whole organism, you can tell your cells what to do. An attention-getting paper in Nature states that “Attention enhances synaptic efficacy and the signal-to-noise ratio in neural circuits.” In other words, when you focus your attention on a sight or sound, your neurons obey, all the way to the level of synapses between neurons. “The results demonstrate that attention finely tunes neuronal communication at the synaptic level by selectively altering synaptic weights, enabling enhanced detection of salient events in the noisy sensory environment.” Philosophers of free will, take note.
Bricks that build: Certain structural building blocks in the inner ear don’t just sit there. They actually have a “starring role” to play, Science Daily reported in a surprise announcement. “Researchers have found in mice that supporting cells in the inner ear, once thought to serve only a structural role, can actively help repair damaged sensory hair cells, the functional cells that turn vibrations into the electrical signals that the brain recognizes as sound.”
Sex cooperation: Science Daily reported a “shocker,” a “surprising finding” that the female X-chromosome participates in sperm production. One would think men and women are actually part of the same species after all.
Where do we stop? We could go on and on. Every week in the science literature, new findings are made about regulators, teams, quality controls (see 7/16/13), checkpoints, conductors, players with starring roles – Michael Denton wasn’t kidding when back in 1985 (Evolution: A Theory in Crisis, p. 328) he compared a cell to a large city, filled with “supreme technology and bewildering complexity.” That was almost 30 years ago; more discoveries have poured forth since then, many of them of paramount importance to our understanding of how life works. It’s almost as if God, in His shrewd wisdom, has allowed biochemists to peer into the machinery, bit by bit, just as they were concluding their “evolution is a fact” speeches through their megaphones in the press. It’s hard to see how Darwinian evolution can survive this never-ending onslaught of Design, design, design! emanating from the living cell as, week after week, year after year, improving technology brings its perfections into sharper focus.