Cell’s are perhaps the most complex machines known to human kind. The sheer diversity of activity, machinery and timing is staggering in its breadth and complexity.
And that raises an interesting question: how is it all co-ordinated? What mechanism do cells use to ensure that crucial biochemical events occur in the right order and at the right time?
Today, Sepehr Ehsani at the University of Toronto in Canada floats an interesting suggestion. His idea is that vibrations in the cell membrane act as a kind of cellular pacemaker, providing a background pulse rate for synchronising activities.
The idea of a pacemaker is common in computer science. Most microchips have an internal clock that synchronises activity across the chip. Information processing as we understand it would not be possible without this pulse.
Cells are essentially information processors too, albeit ones that are far more complex than anything humans have ever made. Many cells use periodic signals such as dark-light cycles to synchronise activity.
However, the circadian cycle is far too slow to help co-ordinate most biochemical activity. Any pacemaking mechanism would probably have to work on the timescale of amino acid folding, which occurs at the microsecond scale.
Internal activities such as cellular energy cycles are fast enough to do the trick but are highly variable across species. And since any pacemaking mechanism must have evolved early in the history of cells, it ought to be shared across the tree of life.
“The remaining alternative is the plasma membrane,” says Ehsani. He points out that the membrane ought to support picosecond vibrations and could easily couple activity outside the cell with what’s going on inside, a factor that might explain various kinds of intercellular communication..
What’s more, the mechanism is easily passed on via evolution and shared across phyla.
Ehsani says that his idea could be easily tested by growing cell cultures in the presence of external vibrations that are designed to interfere with the natural timing mechanism.
Of course, that would require a better understanding of the nature of membrane vibrations, their consistency of over timescales as long as seconds and across phyla.
That’s an interesting suggestion but one that needs significantly more work to be persuasive. Experimental evidence would help but so would some kind of explanation for how the machinery inside a cell could monitor and exploit this signal.
And of course there is another explanation for the complex activity that does not require any kind of pacemaker. Biologists and physicists are well aware that synchrony emerges spontaneously in many complex systems.
This occurs in everything from firefly flashing and brain waves to Huygens’ famous discovery that clock pendulums can become synchronised. And there are sound mathematical models that explain what is going on.
It’s not beyond the realms of possibility that synchrony is an emergent phenomenon in cells that requires no independent pacemaker.
So this is an important question and Ehsani has an interesting hypothesis that is relatively easily testable.
On that basis, it’s surely worth more attention.
Ref: arxiv.org/abs/1210.0168: Time In The Cell: A Plausible Role For The Plasma Membrane