Tau protein is a type of protein primarily found in neurons, where it plays a crucial role in stabilizing microtubules. Microtubules are structural components that help maintain the shape of cells and facilitate the transport of nutrients and other essential materials within the cell. In certain neurodegenerative diseases, such as Alzheimer's disease, tau protein can become hyperphosphorylated, leading to the formation of tangles inside neurons. These tangles disrupt normal cell function and contribute to the degeneration of brain cells, which is associated with cognitive decline and memory loss.