Abstract
Chemical reactions are responsible for information processing in living cells, and their accuracy and speed have been discussed from a thermodynamic viewpoint [1–5]. The recent development in stochastic thermodynamics enables evaluating the thermodynamic cost of information processing [6–8]. However, because experimental estimation of the thermodynamic cost based on stochastic thermodynamics requires a sufficient number of samples [9], it is only estimated in simple living systems such as RNA folding [10] and F1-ATPase [11]. Therefore, it is challenging to estimate the thermodynamic cost of information processing by chemical reactions in living cells. Here, we evaluated the thermodynamic cost and its efficiency of information processing in living systems at the singlecell level for the first time by establishing an informationgeometric method to estimate them with a relatively small number of samples. We evaluated the thermodynamic cost of the extracellular signal-regulated kinase (ERK) phosphorylation from the time series of the fluorescence imaging data by calculating the intrinsic speed in information geometry. We also evaluated a thermodynamic efficiency based on the thermodynamic speed limit [8, 12, 13], and thus this paper reports the first experimental test of thermodynamic uncertainty relations in living systems. Our evaluation revealed the change of the efficiency under the conditions of different cell densities and its robustness to the upstream pathway perturbation. Because our approach is widely applicable to other signal transduction pathways such as the G-protein coupled receptor pathways for sensation [14], it would clarify efficient mechanisms of information processing in such a living system.
Competing Interest Statement
The authors have declared no competing interest.
