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Extracellular calcium signaling
A selection of talks on Biochemistry
The ERK1/2 MAPK cascade
- Prof. Melanie H. Cobb
- University of Texas Southwestern Medical Center at Dallas, USA
Amino acid conjugation: mechanism and enzymology
- Dr. Kathleen Knights
- Flinders University, Australia
Hi, my name is Aldebaran Hofer. Welcome to this lecture on extracellular calcium signaling.
Calcium is at the same time the simplest, yet the most versatile messenger. To put this signaling pathway into perspective, I really like this slide adapted from Sir Michael Berridge, which presents an inventory of the known intracellular signal transduction cascades. As you can see, the calcium ion is highly represented, and in fact, this messenger is recycled for many different purposes to mediate the actions (for example) of G protein-coupled receptors, receptor tyrosine kinases, voltage-operated calcium channels, among others. Most of the other pathways in this list rely on metabolic reactions for their initiation and termination, calcium differs in an important way from these other pathways in that as an inorganic cation, calcium can be neither created nor destroyed. So it's powerful signaling actions can only be controlled by moving the calcium ion about in different locations inside and outside the cell, or by temporarily buffering it.
Calcium moves across the plasma membrane through pathways such as the plasma membrane calcium ATPase (PMCA), or the sodium calcium exchanger, these are important in expelling calcium from the cell. Calcium can enter through pathways such as store-operated, voltage-operated, or receptor-operated calcium channels. All of this transport activity is, of course, exceedingly important in shaping the intracellular calcium signal. However, an interesting corollary of these plasma membrane fluxes is that they can potentially lead to significant alterations in local calcium concentration at the extracellular face of the cell. In today's talk, I'm going to discuss the emerging idea that these calcium fluctuations outside the cell may serve as signals in their own right.