Ion channels are transmembrane proteins that play pivotal role in functioning of human biochemistry. From smell to touch, from stupidity to intelligence, from love to love making depend on firing of action potential in the neuron, the smallest unit of brain. It is very interesting to note that there is only a few ions responsible for initiation of action potential resulting myriad of biochemical functions. Only known ion channels are of Na+, Cl-, K+, Ca2+, Mg2+ ions. Most of these channels are ligand gated i.e. open or close only after binding of small organic molecules followed by transportation of these ions. For examples, we feel happy when serotonin ligand binds K+ ion channel and open it for K+ to rush out of the cell prompting depolarization of inner cell membrane (potential of the inner membrane changes from -60mV to +55mV). This process leads to cascade of protein synthesis switching on or off effector gene. The structural change of the neuron reflects in our everyday mood.
Dumb and Smart Gene
Repeated boost of serotonin is also responsible for converting short term memory into long term memory through extra axonal growth. The more we repeat, the more serotonin gets released to bind with ion channel, firing action potential frequently. A small molecule cAMP builds up inside the cell which in turn activates protein kinase A (PKA, all kinase enzymes phosphorylate another molecule). PKA phophorylates MAP kinase in order to act on a protein CREB-2 and deactivates it. CREB-2 is a regulatory protein which attaches on a gene to switch it off inhibiting protein synthesis for long term memory. On the contrary, PKA activates CREB-1, a regulatory protein binds with a gene to switch it on for protein production. This strengthens the neural connectivity consolidating memory. In a simplistic version, a dumb person is one who has high CREB-2/CREB-1 ratio.
The most interesting part is that one ligand is responsible for two completely different functions (mood change and memory formation) through two separate pathways. Is it possible that there is connection between these two pathways? I believe that we can learn better when we are in good mood (in both cases, serotonin is released). Evolution is minimalist! It uses one molecule available to optimize different functions.
Science Fiction
The ions transport through protein channels on cell membrane are extremely abundant in nature. Na+ and Cl- are probably the most abundant ions found in ocean, evolutionary origin of us. Mg2+ and Ca2+ are also abundant in the rocks. Is there any ion channel for U238 in us? Probably not! U238 is a radioactive element which has disastrous health effect on human. I argue that a world full of U238 would have an evolutionary route to species with U238 channels and radioactive humans! Imagine a world of radioactive isotopic humans. Anything is possible in the universe of infinite worlds.
References:
1. Kandel, Eric. In Search of Memory, W. W, Norton & Company Inc, 2006
2. Jacob, Francois. Evolution and Tinkering, Science, 1977, 196 (4295), 1161-1166
Dumb and Smart Gene
Repeated boost of serotonin is also responsible for converting short term memory into long term memory through extra axonal growth. The more we repeat, the more serotonin gets released to bind with ion channel, firing action potential frequently. A small molecule cAMP builds up inside the cell which in turn activates protein kinase A (PKA, all kinase enzymes phosphorylate another molecule). PKA phophorylates MAP kinase in order to act on a protein CREB-2 and deactivates it. CREB-2 is a regulatory protein which attaches on a gene to switch it off inhibiting protein synthesis for long term memory. On the contrary, PKA activates CREB-1, a regulatory protein binds with a gene to switch it on for protein production. This strengthens the neural connectivity consolidating memory. In a simplistic version, a dumb person is one who has high CREB-2/CREB-1 ratio.
The most interesting part is that one ligand is responsible for two completely different functions (mood change and memory formation) through two separate pathways. Is it possible that there is connection between these two pathways? I believe that we can learn better when we are in good mood (in both cases, serotonin is released). Evolution is minimalist! It uses one molecule available to optimize different functions.
Science Fiction
The ions transport through protein channels on cell membrane are extremely abundant in nature. Na+ and Cl- are probably the most abundant ions found in ocean, evolutionary origin of us. Mg2+ and Ca2+ are also abundant in the rocks. Is there any ion channel for U238 in us? Probably not! U238 is a radioactive element which has disastrous health effect on human. I argue that a world full of U238 would have an evolutionary route to species with U238 channels and radioactive humans! Imagine a world of radioactive isotopic humans. Anything is possible in the universe of infinite worlds.
References:
1. Kandel, Eric. In Search of Memory, W. W, Norton & Company Inc, 2006
2. Jacob, Francois. Evolution and Tinkering, Science, 1977, 196 (4295), 1161-1166
