calciumswitch

Calciumswitch, commonly referred to as the calcium switch, is a concept in cell biology describing how extracellular calcium levels regulate cadherin-mediated cell–cell adhesion. The process is especially studied in epithelial and endothelial tissues where adherens junctions depend on calcium to function.

Cadherins are calcium-dependent transmembrane proteins. Extracellular calcium binds to cadherin repeats, stabilizing their rigid structure and enabling homophilic interactions with cadherins on neighboring cells. In the presence of physiological calcium concentrations, adherens junctions form and maintain tissue integrity. When calcium is chelated and extracellular Ca2+ concentration falls, the cadherin ectodomains lose rigidity, adhesive bonds weaken, and cell–cell contacts disassemble. The switch can occur rapidly, over minutes in cultured cells, and is reversible upon restoration of Ca2+.

Calcium switch assays are commonly used to study junction dynamics and epithelial polarity. In these experiments, cells are grown under normal calcium, then treated with calcium-chelating agents such as EGTA or EDTA to transiently disrupt junctions. After washout and reintroduction of calcium, junctions reform, allowing researchers to examine the kinetics of adhesion reassembly, the dependence on specific cadherins, and the role of signaling pathways in junction maturation.

Beyond basic cell biology, the calcium switch concept has applications in cancer research, tissue engineering, and developmental biology, where control of cell adhesion affects morphogenesis, invasion, and metastasis. Limitations include differences between in vitro assay conditions and the complex calcium environments of living organisms, and the involvement of other calcium-dependent adhesion systems beyond classical cadherins.

Related topics include cadherin, adherens junction, calcium signaling, and the calcium switch assay.