Today is every-other-week recycling day in our town so I made sure our newspapers, magazines, bottles, cans, etc. were out at the curb before leaving for our early morning mall walk. Two weeks ago, I was shocked when the recyclers came through at 6:45 AM, an hour or two earlier than usual and I had just beaten them by a minute or so. Our garbage is picked up once a week on Mondays; it used to be twice a week in the good old days. I know that you couldn’t care less about the details of trash removal from our property. However, it’s my pitiful way to segue into the topic of this week’s column, how the cells in our bodies get rid of their trash. The process is known as “autophagy”.
Oh, I forgot to mention that tomorrow our every-other-week cleaning lady comes for her two-hour stint cleaning and vacuuming. Much the same thing goes on in our cells. There’s a sort of vacuum cleaning and there’s recycling as well. I learned of this from a very interesting article in the May issue of Scientific American titled “How Cells Clean House”. This article on autophagy is authored by two workers in the field, Vojo Deretic at the University of New Mexico and Daniel Klionsky at the University of Michigan. There’s actually a journal, Autophagy, of which Klionsky is the editor in chief.
I often have expressed how I stand in awe of these biological workers who work with such things as DNA, folding of proteins, storing of memories in the brain and what goes on inside the tiny cells of our bodies. The complexity of the multitude of processes that transpire in a cell boggles my mind. I must admit that I hadn’t given any thought to the fact that, with all the complex processes, there has to be some sort of “garbage” that has to be removed or otherwise gotten rid of. Obviously, if sufficient garbage piles up in a cell it’s going to explode or die in some fashion.
Some cells die off in the natural course of events – I’m thinking hair cells and skin cells are in this category. However, some cells stay with us for life and the authors of the article cite neurons in the brain as being one type of cell that in which the detritus of normal operation must be disposed of or recycled expeditiously; otherwise, our memory and other cognitive functions suffer significantly. Alzheimer’s might be one possibility.
OK, let’s cut to the chase. Our cells contain cytoplasm, a kind of jellylike material that surrounds the nucleus of a cell. Cytoplasm contains all kinds of stuff, proteins and lipids, for example. In response to a chemical signal of distress, these lipids and proteins get together to form a double-walled membrane that looks initially like a sliver of an emerging moon that becomes somewhat of a Pac-man. This “Pac-man”, known as a “phagophore”, looks for something out of the ordinary to gobble up. When it does catch something it encircles and becomes a double-walled capsule. In this stage, the capsule containing the wayward entity is known as an “autophagosome”.
One example of something our phagophore would gobble up is a damaged mitochondrion. Mitochondria are the little structures in a cell that generate the energy that drives the functioning of a cell. A mitochondrion works pretty hard generating that energy and in the process gives off oxygen ions and other reactive oxygen compounds. In the process, a mitochondrion can become damaged and start producing more of these reactive oxygen compounds than can be handled. If unchecked, cancer or other diseases might be initiated.
Our little Pac-man phagophore comes upon one of these damaged mitochondria and surrounds it, becoming an autophagosome. Now it goes around in the cell until it meets another capsule called a lysosome; this lysosome capsule contains a bunch of enzymes. The lysosome and phagophore fuse together; now it’s called an “autolysosome”. When the two capsules fuse, the enzymes inside act as recyclers. They go at the damaged mitochondrion and break it down into amino acids. The amino acids are released back into the cytoplasm for reuse. If the cell happens to be a neuron, our brain is happy that autophagy was there to preserve the cell for future use.
This is just a bit about autophagy. If you’re interested, I strongly urge reading the Scientific American article. It’s fascinating what goes on in a cell and what can go wrong when cells either do or do not die when they should. (Cancer is the obvious case when they don’t die.)
If this column seems short, it is. I’m anticipating trouble posting in view of what has happened recently. The first week of the new format on StocksandNews, editor Brian Trumbore essentially did the posting while I looked on. Last week, I posted the column on my own and was quite pleased to find that everything lined up nicely and seemed in order. Then I noticed that, as I scrolled down the column, it seemed much longer than what I had written. It was. Six copies of the column had been posted, one after the other! Happily, I managed to delete five of them.
This week, Brian is in Ireland and I’ve just signed up for one of those cable packages combining phone, Internet and digital TV. So far, I’ve managed the rudiments of the phone and TV but the Internet is giving me problems. In all the years, I’ve worked with computers, at home and at Bell Labs, I’ve never had to call for technical assistance. I think the time has come. I now have three laptops, one with Windows 95 (!!!), one with Millennium and one with XP, all given to me by our editor Brian Trumbore. For these past nine plus years, I’ve been posting my columns on the web site using my dial-up service and the Windows 95 computer. With the new StocksandNews format, I had to go Millennium last week. Now I’m going to see if I can post with the new cable connection. If you see this column, three cheers for Old Bortrum!
Allen F. Bortrum