On 5 Oct 2003 11:01:17 -0700, glucegen at excite.com (Radium) wrote:
>What if both the intracellular and extracellular levels of calcium are zero?
I find it hard to understand your persistence in pursuing this topic.
Although Ca++ is normally held to a very low value inside a cell
(typically below 0.1 micromolar concentration), it is quite essential
for a tremendous number of cell activities.
Whether a cell can sustain a total absence of calcium and recover once
the calcium is restored is debatable. However, a cell simply will not
function without any calcium.
You already know it is essential for contractility and for secretion
including the release of neurotransmitter at the synapse. It is also
absolutely essential for all sorts of other processes. For example
(there are literally hundreds more example)
CM Armstrong and G Cota
Calcium Ion as a Cofactor in Na Channel Gating
Proc. Natl. Acad. Sci. USA. 1991 August 1; 88 (15): 6528-6531
Ubarretxena-Belandia I, Boots JW, Verheij HM, Dekker N.
Role of the cofactor calcium in the activation of outer membrane
Biochemistry. 1998 Nov 10;37(45):16011-8.
Hayakawa Y, Hirashima Y, Yamamoto H, Kurimoto M, Hayashi T, Lee JB,
Mechanism of activation of heparin cofactor II by calcium spirulan.
Arch Biochem Biophys. 2003 Aug 1;416(1):47-52
Wakabayashi H, Schmidt KM, Fay PJ.
Ca(2+) binding to both the heavy and light chains of factor VIII is
required for cofactor activity.
Biochemistry. 2002 Jul 2;41(26):8485-92.
Kornhauser JM, Cowan CW, Shaywitz AJ, Dolmetsch RE, Griffith EC, Hu
LS, Haddad C, Xia Z, Greenberg ME.
CREB transcriptional activity in neurons is regulated by multiple,
calcium-specific phosphorylation events.
Neuron. 2002 Apr 11;34(2):221-33., Neuron. 2002 Apr 11;34(2):179-82.
Regulation of the endoplasmic reticulum calcium storage during the
unfolded protein response--significance in tissue ischemia?
Trends Cardiovasc Med. 2002 Feb;12(2):57-62