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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,
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
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,
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.