It’s been brought to my attention that the scientific terms are beginning to pile up a bit and get in the way of understanding the concepts I am trying to share. (Thanks, Jlynn.) So today let’s try to clear away some of the clutter.
There are two ways to go with scientific terms. You can tell yourself they are only names—just monikers attached to bits of matter—which is essentially true. Or you can try to understand where they came from.
Understanding the origin of a name is only useful if it helps you connect the name and the thing being named. So let me take a shot at helping with that.
Amyloid is a generic term referring to clumps of insoluble protein. You can have amyloid deposition in many disorders, as well as a result of repeated medical procedures like kidney dialysis. The specific protein clumping up and getting deposited varies from disorder to disorder.
All amyloids share certain traits. Most important is insolubility. They are tremendously hard to dissolve, which is the reason deposits build up. The reason they are insoluble has to do with their abnormal 3-D shape, called the beta-pleated-sheet conformation. To a chemist, those italicized words carry meaning and significance. To you and me, all they need to say is insoluble protein.
The name of the specific protein in the amyloid deposits of Alzheimer’s disease is beta-amyloid protein (a.k.a. beta amyloid, nicknamed Aβ for short). There is a long (and boring) story about how that name came to be, but suffice it so say that after much initial disagreement, beta-amyloid is the name that was finally generally agreed upon.
APP stands for amyloid precursor protein (or amyloid protein precursor—depending on whose paper you are reading). This is a big protein (in the neighborhood of 700 amino acid subunits long).
The much smaller (40-42 amino acid subunits) beta-amyloid protein (a.k.a. Aβ) is a small piece snipped out of APP by the secretases discussed last time.
ALPHA, BETA, and GAMMA SECRETASE:
These are the enzymes that act like scissors to cut APP.
Alpha secretase cuts right in the middle of the Aβ part of APP. Any APP molecule that is cut by alpha secretase has had its Aβ portion cut in two, so if half of the APP molecules in a brain are cut by alpha secretase, the potential for Aβ production has been cut in half.
On the opposite side of the coin, beta and gamma secretase work together to free the Aβ section from the big old APP molecule. Beta secretase cuts one end free, and gamma secretase cuts at the other end, releasing Aβ. You only need to stop one of this pair from working to decrease Aβ production.
Together, these three enzymes are called secretases because the protein pieces they cut free are released outside the cell (that is, they are secreted— 😉 . We scientists usually go for the obvious when naming things.)
I’m afraid I can’t be much help with these…
When drug names look like catalog numbers, that is pretty much what they are—someone is testing a bunch of similar compounds and has numbered them. There is no good way to recall these except to have a good memory. Personally, I don’t try to keep them straight in my brain; I just look them up when I need them.
Chemical names of drugs are sometimes used. These carry useful information only if you are chemist enough to understand them… usually I am not that much of a chemist. I treat these the same as the catalog-type names.
Brand names of drugs are assigned by the companies selling them. While these do sometimes carry meaning, more often they are just made up by some marketing guru employed by the pharmaceutical company. If you are an Alzheimer’s caregiver, you probably recognize these more readily than I do. Some of the more common I carry in my brain. But even with those, I look them up to be sure I have it straight when writing about them.
Did that help?
I hope so. Next time we’ll get back in sequence and talk about drugs being developed to prevent aggregation and/or promote the breakdown and removal of beta amyloid deposits.
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