Leakage Channels

Introduction

Leakage channels are also referred to as leak or passive channels. They are one of the many different types of ion channels found in living cell membranes. This is the simplest form of ion channel in our body with only one main rule to follow: simple diffusion and concentration. They are the only nongated ion channel that allows simple ions to flow within membranes and layers. Regardless this is still a vital channel in our body that helps us maintain homeostasis at all times with the equaling out of ions in our body. Since our body is doing this all the time to maintain equilibrium we never truly are in full equilibrium because of this constant change and external stimuli.

Review of Ion Channels

Ion channels are subunits composed of many different things from the body. They are embedded in the cell membrane used to transport ions in different ways. They often contain three components; a selectivity filter, a gate for ion flow, and an ion-permeable pore. These things make up all the different types of channels working in your body all the time. The main one I am going to focus on in this chapter is the selectivity filter which is very prominent in the leakage channels.

When we are talking about equilibrium we are talking about two main types of interactions between electrical and chemical gradients. Electrical gradients is where can push away ions that have the same charge as them like magnets and the opposite can happen with them being attracted to the opposing electric charge. These ions are measured using milli-volts (mV) on the charge of the ion. The chemical reaction is just the second law of thermodynamics which is entropy and diffusion. If there is an area with a high concentration or gradient of one ion those ions will want to move away just because of simple diffusion going on with these leakage channels.

Resting Potential

This is the potential of a cell membrane when that cell is at rest not interacting with any other outside stimuli. This is determined by lots of factors but the main one I am going to talk about is ion charge because that is what determines equilibrium in these leakage channels. Everything that flows through and stays in a membrane has a different resting membrane potential all changing the equilibrium on both sides of the membrane. The most prominent of them all are Sodium (Na) and Potassium (K). These two ions work together going in and out of the cell always trying to find equilibrium. Potassium is more often found trying to leave the cell membrane and sodium is more often trying to get into the cell membrane.

Different Types of Leakage Channels

Sodium (Na+)

One of the main ions sends electrical currents through your body because of the positive charge. They also move around to maintain equilibrium in your body because of the +60mV charge on them. Sodium is useful for things like the activation of neurons, helps contract muscles, is used to maintain a balance of water/minerals, and so much more. Sodium is needed all over the body and that is why we have these sodium leakage channels to be able to get it to where it needs to go using as little energy as possible.

NALCN is the gene for Na+ leakage. Is it the channel that the Na+ can travel through at all times to try and maintain equilibrium.

Potassium (K+)

The potassium channels go hand in hand with the sodium channels in almost everything they do. They work together to get neurons to fire and work against the sodium ions in membrane potential seen in the figure above and below. People don’t often think of potassium as something very important to maintain in their body but, it is so important to maintain because of how it stabilizes the membrane and how it works with sodium ions. Their electrical charge is also so important to maintain because of the membrane potential and how it all works together.

K2P Gene: these are 2-pore domain potassium channels (K2P) that are responsible for the background, leakage currents that stabilize the resting membrane potential and regulate neuronal excitability.

Calcium (Ca2+)

The calcium channel is very important because calcium is used for several different molecular processes like maintaining cell function, muscular contraction, and maintaining an electrochemical gradient. Calcium is regulated by the constant dissolving and building of our bone tissue. It is also regulated by the smooth endoplasmic reticulum (sarcoplasmic reticulum in muscles) because they have calcium storages that are released when acetylcholine is released especially in the muscle. This is important in the muscles because it helps the contraction and relaxation of muscle fibers whenever we move any muscle in our body. Calcium is also very important for bone strength and size.

Aquaporin (H20)

Just like the name suggests it is a leakage channel for water to slip through around the body. Your body uses osmosis to move water across many cell membranes for them to maintain structure and function properly. These are the main ways water spreads around your body to all of your cells. Just like you are told all the time water is very important for your body to function and that is why many cells are areas in your body have this leakage channel because they need water all over always.

References

Boyden, P. A., & Smith, G. L. (2018). Ca²⁺ leak-What is it? Why should we care? Can it be managed? Heart rhythm, 15(4), 607–614. https://doi.org/10.1016/j.hrthm.2017.11.018

Cooper, D., & Dimri, M. (2023). Biochemistry, Calcium Channels. In StatPearls. StatPearls Publishing.

Goldstein, S. A., Bockenhauer, D., O’Kelly, I., & Zilberberg, N. (2001). Potassium leak channels and the KCNK family of two-P-domain subunits. Nature Reviews Neuroscience, 2(3), 175-184.

Kandel, E. R. (2013). Principles of neural science (Fifth ed.). McGraw-Hill Medical

Ren, D. (2011). Sodium leak channels in neuronal excitability and rhythmic behaviors. Neuron, 72(6), 899-911.

Outline by Caleb Bevan, Shelby Pickett, and Avalon Marker