Biology:Calcium-induced calcium release
Calcium-induced calcium release (CICR) describes a biological process whereby calcium is able to activate calcium release from intracellular Ca2+ stores (e.g., endoplasmic reticulum or sarcoplasmic reticulum). Although CICR was first proposed for skeletal muscle in the 1970s,[1] it is now known that CICR is unlikely to be the primary mechanism for activating SR calcium release. Instead, CICR is thought to be crucial for excitation-contraction coupling in cardiac muscle.[2] It is now obvious that CICR is a widely occurring cellular signaling process present even in many non-muscle cells, such as in the insulin-secreting pancreatic beta cells,[3] epithelium, and many other cells.[4] Since CICR is a positive-feedback system, it has been of great interest to elucidate the mechanism(s) responsible for its termination.
Examples in biology
Excitation-contraction coupling
Excitation-contraction coupling in myocardium relies on sarcolemma depolarization and subsequent Ca2+ entry to trigger Ca2+ release from the sarcoplasmic reticulum. When an action potential depolarizes the cell membrane, voltage-gated Ca2+ channels (e.g., L-type calcium channels) are activated. CICR occurs when the resulting Ca2+ influx activates ryanodine receptors on the SR membrane, which causes more Ca2+ to be released into the cytosol.[4][5] In cardiac muscle, the result of CICR is observed as a spatio-temporally restricted Ca2+ spark. The result of CICR across the cell causes the significant increase in cytosolic Ca2+ that is important in activating muscle contraction.
References
- ↑ "Calcium release from the sarcoplasmic reticulum". Physiological Reviews 57 (1): 71–108. January 1977. doi:10.1152/physrev.1977.57.1.71. PMID 13441.
- ↑ "Calcium-induced release of calcium from the cardiac sarcoplasmic reticulum". The American Journal of Physiology 245 (1): C1-14. July 1983. doi:10.1152/ajpcell.1983.245.1.C1. PMID 6346892.
- ↑ "Ca(2+)-induced Ca2+ release in insulin-secreting cells". FEBS Letters 296 (3): 287–91. January 1992. doi:10.1016/0014-5793(92)80306-2. PMID 1537406.
- ↑ 4.0 4.1 "Chapter 26 - Using bilayer lipid membranes to investigate the pharmacology of intracellular calcium channels". Membrane Science and Technology. Planar Lipid Bilayers (BLMs) and Their Applications. 7. Elsevier. January 2003. pp. 723–734. doi:10.1016/s0927-5193(03)80050-5. ISBN 9780444509406.
- ↑ "Calcium-Induced calcium release during action potential firing in developing inner hair cells". Biophysical Journal 108 (5): 1003–12. March 2015. doi:10.1016/j.bpj.2014.11.3489. PMID 25762313. Bibcode: 2015BpJ...108.1003I.
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