The organisation and functions of local Ca(2+) signals.

Calcium (Ca(2+)) is a ubiquitous intracellular messenger, controlling a diverse range of cellular processes, such as gene transcription, muscle contraction and cell proliferation. The ability of a simple ion such as Ca(2+) to play a pivotal role in cell biology results from the facility that cells have to shape Ca(2+) signals in space, time and amplitude. To generate and interpret the variety of observed Ca(2+) signals, different cell types employ components selected from a Ca(2+) signalling 'toolkit', which comprises an array of homeostatic and sensory mechanisms. By mixing and matching components from the toolkit, cells can obtain Ca(2+) signals that suit their physiology. Recent studies have demonstrated the importance of local Ca(2+) signals in defining the specificity of the interaction of Ca(2+) with its targets. Furthermore, local Ca(2+) signals are the triggers and building blocks for larger global signals that propagate throughout cells.