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The Release of Calcium Ions is a Key Event in
Many Signaling Processes
• Many signal molecules in animals induce responses in
their target cells via signal-transduction pathways that
increase the cytosolic concentration of Ca2+.
– Signal-transduction pathways trigger the release of Ca2+ from the cell’s ER.
• The pathways leading to release involve still other
second messengers, diacylglycerol (DAG) and inositol
trisphosphate (IP3).
– Both molecules are produced by cleavage of certain phospholipids in the plasma
membrane.
• Cells use Ca2+ as a second messenger in both G-protein
pathways and tyrosine-kinase pathways.