Cadherins
Summary
Cadherins are Ca²⁺-dependent transmembrane proteins that bind one cell to another, usually by binding the same cadherin type on the neighboring cell. They anchor adherens junctions (via actin) and desmosomes (via intermediate filaments). Testable: removing Ca²⁺ weakens cadherin adhesion.
Detail
Meaning: Cadherins are transmembrane glycoproteins that hold neighboring cells together, and they require extracellular Ca²⁺ to bind. They usually bind the same cadherin type on the adjacent cell (homophilic binding), so cells with matching cadherins stick together and sort into tissues. Inside the cell, classical cadherins link through catenins to actin in adherens junctions; desmosomal cadherins link to intermediate filaments in desmosomes.
On the MCAT: Passages describe cells that clump in culture but separate when Ca²⁺ is chelated (for example by EDTA) or an anti-cadherin antibody is added. Questions ask you to match the molecule to its job: cadherins join cell to cell. Loss of E-cadherin in tumor cells is linked to detachment and invasion, so predict reduced adhesion.
Common confusion: Cadherins are mixed up with integrins and selectins. Integrins are αβ heterodimers that bind extracellular matrix such as fibronectin and collagen (focal adhesions, hemidesmosomes). Selectins bind carbohydrates and mediate leukocyte rolling. Tight junctions rely on claudins and occludin, not cadherins.
Sources
- Molecular Biology of the Cell
- Lehninger Principles of Biochemistry
- Campbell Biology
Written for the MCAT and checked before it was published. For study reference only. Spotted an error? Let us know.