Ca2+ signalling

Short (typically lasting no more than a few seconds) increases in cytosolic Ca2+ concentration that periodically interrupts the stable resting level. Many Ca2+ signals are delivered to cells as frequency-coded Ca2+ spikes. 

IP3 Receptors. Figure 1 Interplay between Ca2+ channels. Ca2+ signals are initiated when an extracellular stimulus (red) directly opens a Ca2+ channel in the plasma membrane or indirectly, via a signalling pathway (green), opens an intracellular Ca2+ channel. Ca2+ signals may then be propagated across the cell by Ca2+-induced Ca2+ release mediated by IP3R or RyR. 

All the RyR channels are gated by cytoplasmic Ca2+, known as Ca2+-induced Ca2+ release (CICR). CICR functions as an amplifier of small Ca2+ signals in various excitable and non-excitable tissues and well documented in E-C coupling in the heart. In addition, RyRl can also mediate depolarization-induced Ca2+ release (DICR) , which is controlled by some protein-protein interactions. DICR is the principal Ca2+ release mode in E-C coupling in the skeletal muscle. 

Bums JM, Lewis GK, DeVico AL. Soluble complexes of regulated upon activation, normal T cells expressed and secreted (RANTES) and glycosaminoglycans suppress HIV-1 infection but do not induce Ca2+ signaling. Proc Natl Acad Sci U S A 1999 96(25) 14499-14504. 

Uramura K., Funahashi H., Muroya S. et at (2001). Orexin-a activates phospholipase C- and protein kinase C-mediated Ca2+ signaling in dopamine neurons of the ventral tegmental area. NeuroReport 12, 1885-9. 

Eukaryotes (single cell) Plant-like Fungal-like Animal-like Cholesterol in cell s membrane compartments, nucleus, filaments, Ca2+ signals Photosynthetic, sedentary Dependent on plants, sedentary Dependent on digestion, mobile Use of Cu, Zn... 

Meinrenken, C. J., Borst, J. G. and Sakmann, B. Local routes revisited the space and time dependence of the Ca2+ signal for phasic transmitter release at the rat calyx of Held. J. Physiol. 547 665-689,2003. 

The addition of CaBPs can directly activate the IP3-R in a Ca2+-dependent manner, via interaction with the N-terminus region of the receptor. This raises the possibility that CaBPs can act on IP3-Rs to potentiate the Ca2+ signals that arise from other sources, e.g. ligand-gated ion channels. 

Periodic temporal and spatial patterns of Ca2+ signaling give rise to calcium oscillations and waves 384... 

Ca2+-signaling events in excitable and nonexcitable cells, although distinct, share some common characteristics 387... 

The interaction of IP3 with its receptor involves complex and poorly understood regulatory interactions among the receptor, IP3 and Ca2+ - the latter apparently exerting influence from both the cytoplasmic and luminal aspects of the receptor. Ca2+ in the lumen of the ER appears to sensitize the receptor to IP3. On the cytoplasmic surface, low concentrations of Ca2+ sensitize while higher concentrations are inhibitory. These actions may contribute to the all-or-none oscillatory behavior of [Ca2+] signals seen in some cell types. This phenomenon will be discussed in more detail below. 

Ca2+-signaling events in excitable and nonexcitable cells, although distinct, share some common characteristics. Traditionally, calcium-signaling studies have been divided into two separate categories studies focusing on excitable cells, such as nerve and muscle, and studies focusing on electrically nonexcitable cells, such as... 

Brini, M. Ca2+ signaling in mitochondria mechanism and role in physiology and pathology. Cell Calcium 34 399 105,2003. 

Stimulation of a cell by first messengers that increase cellular Ca2+ concentrations similarly activates CREB (Fig. 23-9). This appears to occur via the phosphorylation of CREB on serine 133 by a CaMK, probably CaMKIV as well as, possibly, CaMKI. It remains to be established whether the activated kinase translocates to the nucleus, by analogy with the catalytic subunit of the cAMP kinase, or whether elevated Ca2+ signals enter the nucleus and activate the kinase already there. Interestingly, phosphorylation of CREB on a distinct serine residue, serine 142, by CaMKII appears to inhibit the transcriptional activity of CREB in vitro, although whether this inhibitory effect occurs in vivo is unknown. 

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