Spectrin is a structural protein that plays a crucial role in maintaining the shape and flexibility of the cell membrane, especially in red blood cells. It is a cytoskeletal protein that forms a lattice-like network beneath the cell membrane, providing support and stability to the cell's structure. Spectrin interacts with other cytoskeletal proteins, such as actin, to form the cytoskeleton. In red blood cells, the spectrin-actin network is essential for the biconcave shape and deformability of the cells, allowing them to squeeze through narrow capillaries. Mutations or deficiencies in spectrin can lead to conditions like hereditary spherocytosis, characterized by spherical-shaped and less flexible red blood cells.