SysBioSig ligand and three-node signaling network symbolSysBioSig

Systems Biology of Cellular Signaling
IPPT PAN · Warsaw, Poland

Questions & approaches

Research

Our work aims to go beyond reductionist descriptions of cellular signaling by understanding how interactions between components shape the behavior of the whole system.

We combine systems biology and information theory to ask how individual cells interpret complex signals and translate them into distinct actions. This perspective connects our studies of signaling dynamics, cell-to-cell variability and cross-wired networks.

Cellular signaling

Cells communicate by releasing molecules such as hormones, growth factors and cytokines. Receptors detect these signals and activate networks of proteins inside the cell, connecting changes in the environment to a cellular response.

These networks are interconnected, and apparently similar cells can respond differently to the same signal. We study how signaling dynamics, cellular variability and pathway architecture work together, asking how cells interpret complex signals reliably and what this means for coordinated biological function.

Extracellular signals are received by membrane receptors and passed through an interconnected intracellular network.
Signals reach distinct effectors through interconnected pathways.Conceptual illustration

Information theory

We view a signaling pathway as a communication channel: a stimulus is the input, and a cellular response is the output. Because the same input can produce a range of responses, interpreting the signal involves uncertainty.

Information theory gives us tools to quantify that uncertainty. Shannon information capacity measures how much information the channel can transmit, while Fisher information describes how sensitively response distributions change with the input. We investigate how signaling dynamics, network connections and cellular states affect the ability to distinguish stimuli, and how these limits help explain the organization of signaling systems.

Two schematic communication channels compare overlapping response distributions with more distinguishable responses.
Less overlap between response distributions makes input signals easier to distinguish.Conceptual illustration

Cell-to-cell variability

Genetically similar cells exposed to the same stimulus can show very different responses. This variability can reflect random fluctuations in molecular reactions, but also differences in cellular states, such as the amounts or activity of signaling components.

Distinguishing these possibilities matters: a broad spread of responses across a population does not, by itself, tell us how precisely each cell senses its environment. We combine quantitative experiments and mathematical analysis to understand what drives heterogeneous responses and how reliable signaling can emerge at the level of individual cells and populations.

Cells exposed to the same signal show different levels of intracellular activation; response envelopes are schematic.
The same stimulus can produce different responses across individual cells.Conceptual illustration

Cross-wired signaling

Cellular signaling is rarely organized into fully separate pathways. A single ligand can activate several effectors, and a single effector can respond to several ligands. This shared use of signaling components creates networks with overlapping inputs and outputs.

We ask why this architecture is so widespread, how it arose during evolution, and what its advantages and limitations are. In particular, we study how the overlap between pathways affects information transfer: when can a cell still distinguish signals, and when do shared components constrain the range of responses it can resolve?

No divergenceComplete divergencePartial divergence
Three conceptual networks compare no divergence, complete divergence and partial divergence of ligand–receptor interactions.
Alternative patterns of ligand–receptor connectivity.Conceptual illustration