Question

1. How are waves of Ca2+ generated in cells? How might oscillating waves provide an added dimension for encoding information?

2. Why is specificity a particularly acute problem for small signaling mediators such as cAMP? How do scaffold proteins mitigate this issue?

Answer 1

1) Cytosolic Ca2+ waves can be generated after stimulation by hormones,neurotransmitters,or treatments which promote Ca2+ influx into the cells.This wave may result from cell membrane depolarization propagation,through voltage-operated channels,calcium-induced calcium release etc.During cell signalling through IP3-DAG pathway,IP3 can induce calcium release from ER via opening of calcium-gated channels.Thus calcium-waves are generated inside cells.

Calcium acts as a second messenger,through binding to calmodulin.calcium-calmodulin complexes activates protein kinase and other target proteins which enter the nucleus and regulate gene expression.In non-excitable cells, calcium regulates transcription, cell cycle progression or apoptosis.In excitable cells, these functions include muscle contraction or neurotransmitter release.Thus oscillating calcium waves add dimension for encoding information.