The mystery of nerve cell behaviour could be solved with a recent study of how calcium affects cellular responses
SCIENTISTs at the MRc Laboratory of
Molecular Biology in Cambridge, UK,
claim to have unearthed a significant
relationship between calcium present
in our bodies and cellular responses.
Calcium plays an important role in
various physio -biological functions
ranging from normal development
to illness and cell death. Besides, the
calcium atom - more appropriately,
the calcium ion - is an important agent
of signalling between the cells of
our body or between the environment
and a cell. A whole range of external
signals first elicit a rise in the calcium
content of a cell; this rise tells the
cell what it has to do. The rise can be
caused by either an entry of calcium
from the outside or by a release of
the calcium that is stored in special
compartments inside the cell. Often,
an increase in cellular calcium is accompanied by an increase in the level of
calcium in the nucleus of the cell. It
had been believed that this was a passive
consequence of a leak from the main
body of the cell, the cytoplasm, into the nucleus.
The study - involving a combination of micro-injection and state-of-
the-art fluorescence microscopy - by
G E Hardingharn, Sangeeta Chawla and
colleagues at MRC Laboratory has
thrown this belief overboard. It has
shown that calcium in the nucleus and
calcium in the cytoplasm act as two
different signals and control two
different kinds of responses in the cell
(Nature, Vol 385, No 6615).
The researchers injected a dye,
BAPTA, into the nucleus of cells removed
from the pituitary gland of a mouse.
BAPTA binds calcium very tightly. When
cells were stimulated after this procedure, the rise in cytoplasmic calcium
was as expected but the rise in nuclear
calcium was reduced by half It was seen
that blocking the increase in nuclear
calcium prevented the rise in activity of
a particular gene that was normally
evoked by the stimulus. However, not
only did BAPTA affect the increase in
cytoplasmic calcium caused by the stimulus, the expression of a second gene that was known to be activated thereby was also unaffected.
The finding essentially points
out that when stimulated, a cell has
some means of knowing whether it
should respond by a decrease in the
nuclear calcium pool, or by an increase
in the cytoplasmic calcium pool.
The two patterns of increase lead to
correspondingly different patterns of
gene activity.
We are a voice to you; you have been a support to us. Together we build journalism that is independent, credible and fearless. You can further help us by making a donation. This will mean a lot for our ability to bring you news, perspectives and analysis from the ground so that we can make change together.
Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.