For only beginning our second week, it feels a lot like being in the middle of a semester.
You know the feeling: you’re carrying something heavy (a giant wooden desk, for instance), and you’re about halfway to where you’re trying to take it (a moving van, say). Your fingers start cramping, palms begin sweating; you have this vision of dropping it mid-stairway, right onto your toes…
So I’m about to dive deep into an all-(Sun)day study session, but first I want to share something near and dear to my heart: the iron-dependent regulation of transferrin-receptor (TfR) mRNA.
Are you rolling your eyes?
I don’t want to get into the nitty-gritty details. (I mean, I DO want to, I just don’t have time. Also, I already described it in detail to Hubs, and his reaction brought me down to earth again–God bless him for loving me.)
But basically, there is a special mechanism through which your cells control how much iron is brought into each cell. There is a specific little mRNA sequence (think of mRNA like Ikea instructions) that tells that cell to make a protein that brings extracellular iron into the cell. When the cell has too much iron, this mRNA piece needs to be told to stop making more iron-recruiters. But how? The mRNA contains these “weak” sequences that allow it to be degraded by the cell. (If we’re sticking with the Ikea metaphor, imagine that key words of your instructions are randomly flipped from English to Swedish.)
The coolest part is that, when iron levels are low, there are these special little protective caps called IRE-BP that bind to these weak “key words” and protect the mRNA from being degraded by the cell, thereby allowing the mRNA to keep commanding the cell to make theses iron-recruiting protein guys to raise the intracellular iron levels. (Or you to keep assembling your Ikea desk or whatever.)
So if you think about the complexity of this one process just for a moment, and think about how many things could go wrong (a mutation in the mRNA, a misfolded protein, a problem with the IRE-BPs, etc)–then back up and think of ALL the other things that that one cell requires to survive (calcium, sodium, water, magnesium–just read the back of a vitamin bottle).
Now back up further and think of how many many MANY cells you have in your body, and how different classes of different cells need different things at different levels–and some even have different regulatory pathways. I really don’t think anyone has to be as nerdy as I am to appreciate the awe-inspiring complexity of the human body. Considered this way, it’s really hard for me to think of life as anything other than Divinely created and organized. And absolutely amazing.
The Nontraditional Medical Student 