Calcium signaling
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During calcium signaling calcium ions act as second messengers in signal transduction. Second messengers are intracellular signals that mediate physiological processes. Important physiological roles for calcium signalling include muscle contraction, and the cellular motility, including the movement of flagella and cilia. Other biochemical roles of calcium include regulating enzyme activity, ion pumps, and components of the cytoskeleton.
Signaling occurs when the cell is stimulated to release calcium ions (Ca2+) from intracellular stores. The resting concentration of Ca2+ in the cytoplasm is normally maintained in the range of 10 - 100 nM. To maintain this low concentration, Ca2+ is actively pumped from the cytosol and accumulated in the endoplasmic reticulum (ER), and sometimes in the mitochondria. Certain proteins of the cytoplasm and organelles act as buffers by binding Ca2+.
Specific signals can trigger a sudden increase in the cytoplasmic Ca2+ level up to 500 - 1 000 nM by opening channels in the endoplasmic reticulum or the plasma membrane. Many of Ca2+-mediated events occur when the released Ca2+ binds to and activates the regulatory protein calmodulin.
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- Koolman, Roehm. Color Atlas of Biochemistry. Thieme, 2005 ISBN 1-58890-247-1
| Cell signaling |
|---|
| Key concepts - Ligand | Receptor | Second messenger | Protein kinase | Transcription factor | Cell signaling networks |
| Pathways - Apoptosis | Ca2+ signaling | Cytokine signaling | Hedgehog | Integrin signaling | JAK/STAT | Lipid signaling | MAPK/ERK pathway | mTOR | NF-kB | Notch | p53 | TGFβ | Wnt |
| Calcium signaling |
|---|
| Second messengers: IP3 | NAADP | cADPR |
| Intracellular calcium store gates: IP3 receptor | Ryanodine receptor | putative NAADP receptor |
| Calcium pumps and exchangers: SERCA | Na/Ca antiport | Ca/H antiport |
| calcium binding protein domains: EF hand domain | C2 domain |
| Calcium based molecular switches, and kinases: troponin c | CaM | CaM kinases | PKC | NCS |
| Intracellular Calcium chelators (calcium buffers) and calcium sensors: Calbindin | S100 | pervalbumin | Calretinin | Calsequestrin | Sarcalumenin | Phospholamban | Synaptotagmins |
| Calcium dependent proteases: Calpain |
| Calcium dependent cytoskeleton remodeling proteins: Gelsolin |
| Cell membrane calcium channels: VDCC | TRP | NMDA receptor | AMPA receptor | 5-HT3 receptor | P2X Receptor |
| Calcium regulated chaperones: calreticulin | calnexin |
| Calcium based adhesion molecules: cadherin |
| Calcium homeostasis |
| parathormone | Calcitonin | calcium receptor | vitamin D |
