Assistant Professor Matthias Schneider (ME) has found evidence of a highly efficient means of communication between cells and proteins: they “talk” to each other. In other words, acoustic signals propagate from one cell or protein to another, thereby signaling their neighbors to take a specified action.
Schneider, two of his graduate students—Josef Griesbauer and Stefan Bössinger—and a former colleague from the University of Augsburg in Germany, Achim Wixforth, describe their research in the May 9 online edition of Physical Review Letters. Their study is highlighted as an “Editors’ Suggestion,” indicating its far-reaching, interdisciplinary impact.
“Our findings support the controversial idea that sound propagation is the basis of inter- and intra-cellular communication and the foundation of nerve pulse propagation,” Schneider maintained. “This may lead to a fundamentally new way of thinking about organs, including the brain, and to novel approaches in treating organ disease and the engineering of artificial organs.”
Scientists have long identified two mechanisms for inter- and intracellular communication—immediate contact, in which proteins on the membranes of two neighboring cells collide; and diffusion, in which a protein on one cell membrane dispatches particles through the cell that eventually impact another protein or cell.
Schneider’s efforts to uncover a third mechanism—acoustic waves—stems from the work of Albert Einstein and Konrad Kaufmann (a former mentor of Schneider’s) and the realization that the inner landscape of individual cells is crowded with a network of two-dimensional ridges, known as “interfaces,” that form a distinct, continuous pathway leading from one end of a cell to another or even connecting multiple cells. Over the past two years, Schneider and his collaborators have conducted experiments to show that 2D acoustic waves propagate along these interfaces, just as sound travels through air.
Their results suggest that proteins attached to neighboring cells can “communicate” across the continuous 2D interfaces via acoustic waves, potentially enabling biological activities that range from energy consumption to digestion.
The researchers created a prototypical interface by spreading soap-like lipid molecules from a cell membrane onto a water surface. Once the lipids formed a two-dimensional film, they added a solvent such as ethanol or chloroform to excite one end of the film and produce an acoustic wave, and used a pressure sensor to measure unmistakable changes in pressure at the other end of the film.
“We’ve shown that a sound wave can propagate through these interfaces from one end of the film to the other, compressing and expanding them along the way,” said Schneider. “Similarly, as acoustic waves propagate along a cell’s interfaces, a protein on one end of the cell may ‘feel’ the pressure and other changes ‘communicated’ from the other end.”
To confirm this phenomenon in living systems, Schneider plans to investigate sound wave propagation in algae, earthworm and, ultimately, human cells.
“The idea presented is a major step for one of the most fundamental questions in science, ‘Can physics explain life?’ explored most notably in physicist Erwin Schrödinger’s book, What is Life?” said Schneider. “It’s not that we can say ‘yes’ yet, but we can say, ‘There is no reason to believe it cannot, and we just demonstrated why we should go ahead on Schrödinger’s quest.’”