Releases transmissions/ signals, helps communication between cells (axon terminal)
For this "specialized cell" I thought it would be interesting to have a cell that would have effects similar to that of caffeine, but without actually having any caffeine. Basically, I wanted this cell to be able to replace sleep. For the structure, I thought it would be really similar to that of a neuron, since it would have to sense signals from the brain in order to know that you were tired, and then transmit signals back to the brain to reverse it. Real neurons have to transmit signals all throughout the nervous system, but this cell would focus on transmitting signals to the brain. Even though the signals it has to transmit have to be stronger, the axon would be shorter, since the signal has to be transmitted a shorter distance.
The purpose of these cells would be to (somehow) replace sleep. It wouldn't be able to completely replace it, but the idea was that it would allow you to feel less tired, which is something I think we would all need once in a while. Now, why not just drink coffee? Or something that contains caffeine? Well, with this cell, you wouldn't have too. (Plus, it's just a concept, this most likely wouldn't work in real life.)
The location of this specialized cell would be The Brain. The function of this cell is to combat exhaustion, and to act as a "sleep supplement" in a way. Because of this, I believe it would take place within the brain, as that is what releases signals when you're tired; thus the caffeine cell would have to be in the same place to counteract (or transmit) signals to reduce that. In fact, this works really well with what already exists in the brain, as there can be over 10 million neurons in them to pick up and transmit the signals that are being released.