E-cadherin is a fundamental protein that connects cells, acting like a cellular glue. Found widely in tissues that form linings and coverings, such as skin and organ surfaces, it maintains the structural integrity and organization of various bodily structures.
Understanding E-cadherin
E-cadherin, or epithelial cadherin, is a cell adhesion molecule (CAM) belonging to the cadherin family. It forms adherens junctions, specialized structures on the surface of epithelial cells that allow them to adhere tightly.
The mechanism by which E-cadherin functions involves a precise interaction between E-cadherin molecules on one cell and those on a neighboring cell, much like a zipper fastening two pieces of fabric. This “zipping” action is dependent on the presence of calcium ions, which help to stiffen the E-cadherin molecules, allowing them to form stable connections.
Inside the cell, the E-cadherin protein extends through the cell membrane and connects to a network of internal proteins called catenins, including beta-catenin and alpha-catenin. These catenins, in turn, link E-cadherin to the cell’s internal scaffolding, known as the actin cytoskeleton. This connection to the cytoskeleton ensures that the cell-to-cell adhesion is not just superficial but is also mechanically integrated with the cell’s structure, influencing its shape and movement.
E-cadherin’s Role in Tissue Health
E-cadherin’s adhesive function supports the health and proper functioning of epithelial tissues, which cover external surfaces and line internal organs. It maintains the organized architecture of these tissues, ensuring cells are arranged correctly and form continuous, stable layers.
The protein also contributes to cell polarity, which is the organized arrangement of cellular components and functions within a cell. Proper polarity is essential for tissues to perform their specialized tasks, such as absorption or secretion. The continuous connections formed by E-cadherin help to establish and maintain this organized cellular orientation.
Beyond simply holding cells together, E-cadherin plays a role in the barrier function of epithelial tissues. For example, in the skin or the lining of the gut, E-cadherin helps to create a tight seal that prevents harmful substances from entering the body while allowing necessary nutrients to pass through. This barrier is fundamental for protection and normal physiological processes.
E-cadherin is also involved in cell signaling and differentiation, processes that contribute to healthy tissue development and maintenance. It influences how cells communicate and mature into specialized types, helping prevent uncontrolled cell growth. This broader role highlights its importance in tissue homeostasis, ensuring tissues remain stable and functional.
E-cadherin and Disease
When E-cadherin function is compromised or lost, it has consequences for tissue health, particularly in cancer progression. E-cadherin is often referred to as a tumor suppressor protein because its presence restricts cells from becoming invasive.
Loss of functional E-cadherin allows cells to detach from the primary tumor mass. This detachment is a step in tumor invasion, where cancer cells break away from their original location and move into surrounding tissues. The reduction in cell-to-cell adhesion makes it easier for these cells to become migratory.
Following invasion, the loss of E-cadherin also facilitates metastasis, the spread of cancer cells to distant parts of the body. Once detached, these cells can enter the bloodstream or lymphatic system and travel to new sites, forming secondary tumors. Studies have shown that re-activating E-cadherin’s adhesive function can inhibit metastasis at multiple stages, including reducing circulating tumor cells and their ability to establish new growths.
While the loss of E-cadherin is strongly linked to cancer progression, particularly in aggressive forms of epithelial cancers like gastric or breast cancer, some metastases can still retain E-cadherin expression. In these cases, it is often a change in the functional activity of E-cadherin, rather than its complete absence, that allows for continued cell migration and tumor spread.