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.[1]
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.
After cytoplasmic calcium has been depleted, Ca2+ can be imported from outside the cell by activation of SOC channels. This inflowing calcium current that results after stored calcium reserves have been released is referred to as Ca2+-release-activated Ca2+ current (ICRAC). The mechanisms through which ICRAC occurs are currently still under investigation, although two candidate molecules, Orai1 and STIM1 have been linked by several studies, and a model of store-operated calcium influx, involving these molecules, has been proposed. Recent studies have cited the phospholipase A2 beta,[1] nicotinic acid adenine dinucleotide phosphate (NAADP),[1] and the protein STIM 1[1] as possible mediators of ICRAC.
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Cell signaling | |
|---|---|
| Key concepts | Ligand - Signal transduction - Apoptosis - Second messenger system (Ca2+ signaling, Lipid signaling) |
| Processes | Paracrine - Autocrine - Juxtacrine - Neurotransmitters - Endocrine (Neuroendocrine) |
| Types of proteins | Receptor (Transmembrane, Intracellular) - Transcription factor (General, Preinitiation complex, TFIID, TFIIH) - Adaptor protein |
| receptor ligands | hormones, neurotransmitters, cytokines, growth factors |
Cell signaling: 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 | Parathyroid hormone - Calcitonin - calcium receptor - vitamin D |
Acknowledgement and Attribution Regarding Sources of Content
Some of the initial content on this page may be incorporated in part from copyleft sources in the public domain including wikis such as Wikipedia and AskDrWiki. Drug information for patients came from the The National Library of Medicine. Infectious disease information may have come from the Centers for Disease Control (CDC). Differential Diagnoses are drawn from clinicians as well as an amalgamation of 3 sources: 1.The Disease Database; 2. Kahan, Scott, Smith, Ellen G. In A Page: Signs and Symptoms. Malden, Massachusetts: Blackwell Publishing, 2004:3; 3. Sailer, Christian, Wasner, Susanne. Differential Diagnosis Pocket. Hermosa Beach, CA: Borm Bruckmeir Publishing LLC, 2002:7 .
