Calcium signalling cascades

Definition

Calcium signalling cascades are cellular signalling pathways in which the calcium ion (^Ca2+) assumes central functions as a secondary messenger substance. They enable the cell to convert external stimuli into specific reactions.

Function and significance

^Ca2+ acts as a versatile signalling molecule. Even the smallest changes in concentration can trigger far-reaching cellular responses.

Mechanism of the calcium signalling cascade

Signalling induction: Activation of cell receptors by stimuli.
Calcium release:
- Inflow of ^Ca2+ through membrane channels
- Release from intracellular stores (ER)
Signal transmission:
- Activation of calmodulin, CaMKs, calcineurin
- Triggering of cell responses: contraction, secretion, gene expression
Signalling shutdown: ^Ca2+ return transport into storage or to the outside

Physiological and pathological significance

Important for: muscle movement, neuronal communication, immune response, cell growth

Disruptions lead to: cardiac arrhythmia, neurodegenerative diseases, cancer

Example: Neuronal calcium signalling cascade

Action potential reaches presynaptic termination
^Ca2+ flows into the cytosol via channels
Vesicles fuse with membrane
Neurotransmitters are released

Summary

Calcium signalling cascades are essential, finely tuned mechanisms of cell communication. Their versatility makes them central players in biological processes and at the same time susceptible to pathological disorders.