Know the Single-Receptor Sensing Limit? Think Again

Abstract

How cells reliably infer information about their environment is a fundamentally important question. While sensing and signaling generally start with cell-surface receptors, the degree of accuracy with which a cell can measure external ligand concentration with even the simplest device—a single receptor—is surprisingly hard to pin down. Recent studies provide conflicting results for the fundamental physical limits. Comparison is made difficult as different studies either suggest different readout mechanisms of the ligand-receptor occupancy, or differ on how ligand diffusion is implemented. Here we critically analyse these studies and present a unifying perspective on the limits of sensing, with wide-ranging biological implications.Electronic supplementary materialThe online version of this article (doi:10.1007/s10955-015-1412-9) contains supplementary material, which is available to authorized users.

hunchbackPromoters Can Readout Morphogenetic Positional Information in Less Than a Minute

“…However, none of these approaches can result in a precise anterior-posterior (AP) decision for the hunchback promoter in the short time of the early nuclear cycles, which has led to the conclusion that there is not enough time to apply the fixed-time Berg-Purcell strategy with the desired accuracy [23]. Additional mechanisms to increase precision (including internuclear diffusion) do yield a speed-up [24,25], yet they are not sufficient to meet the 3 minutes challenge. The issue of the embryological speed-accuracy tradeoff remains open.…”

Mixed analytical-stochastic simulation method for the recovery of a Brownian gradient source from probability fluxes to small windows

“…Bacteria and spermatozoa can orient themselves in various chemotactical or mechanical gradients [2,11]. However, most models in the current literature that are concerned with addressing these questions rely on computing the flux to an absorbing or reflecting ball [4], an absorbing or permeable ball [9,1], or a single receptor sphere [17], all of which is insufficient to differentiate between concentrations to the left or right of the cell. To enable sensing of this difference, the detectors, modeled here as small absorbing windows, should be considered individually.…”

Optimal inference strategies and their implications for the linear noise approximation

“…In an information theoretic language the ML estimate "uses" 0.5 bit more information from the history of the receptor occupancy than the BP estimate. Further studies have examined ML estimates for concentration ramps [3,4], for spatial gradients [5], and for competing signals [6] (see [7,8] for recent reviews). Most prominently, it has been elucidated that this additional information cannot be reached within the class of linear models [9,10], which illustrates the inherent loss of information for this specific class of inference strategies.…”