1.16.14 Signaling Crosstalk Definition

Signaling Crosstalk Definition is a description of the phenomenon in which the activity of one signaling pathway influences the activity of a separate, otherwise distinct signaling pathway, occurring through shared components, direct molecular interactions between components of the two pathways, or competition for common regulatory resources, such that the behavior of either pathway can no longer be fully understood by considering that pathway in isolation from the other.

Conceptual Basis

Interaction Between Otherwise Distinct Pathways

Signaling crosstalk is defined by an interaction occurring between two or more signaling pathways that would, in the absence of this interaction, be considered functionally separate and independent, distinguishing crosstalk from the internal structure of a single pathway, such as its own internal branch points or feedback loops.

A Departure From Strict Pathway Independence

Signaling crosstalk represents a departure from the simplified view of signaling pathways as strictly independent, non-interacting chains of activation, reflecting instead the reality that the signaling pathways operating within a cell frequently exert mutual influence upon one another through a variety of mechanisms.

Mechanisms of Crosstalk

Shared Components

Crosstalk can occur when two distinct signaling pathways share a common component, such that activation of one pathway necessarily engages this shared component, which in turn also participates in and influences the activity of the second pathway, coupling the behavior of the two pathways through this point of overlap.

Direct Interaction Between Components

Crosstalk can also occur through a direct molecular interaction between a component of one pathway and a component of a separate pathway, in which a protein belonging to one signaling pathway physically binds to or chemically modifies a protein belonging to the other, influencing the second pathway's activity through this direct contact.

Competition for Shared Resources

Crosstalk can arise through competition between distinct pathways for a shared, limited resource, such as a common regulatory protein or a common downstream binding partner, such that increased engagement of that resource by one pathway reduces its availability to the other, indirectly coupling the activity of the two pathways.

Consequences of Crosstalk

Modulation of Pathway Output

Because crosstalk allows the activity of one pathway to influence a separate pathway, the ultimate signaling output produced by a given pathway can depend not only on the specific signal that engaged that pathway directly, but also on the concurrent activity of other pathways interacting with it through crosstalk.

Integration of Multiple Signaling Inputs

Signaling crosstalk provides a mechanism through which a cell can integrate information arising from multiple distinct signaling contexts into a coordinated overall response, rather than processing each pathway's input entirely separately and without reference to the others.

Relationship to Signaling Pathways and Cancer Cell Biology

An Emergent Property of the Broader Signaling Network

Signaling crosstalk is best understood as an emergent property of the broader signaling network within a cell, arising from the interconnections among individually definable pathways and contributing to the overall complexity of how a cell integrates and responds to its full range of concurrent signaling inputs.

A Contributor to the Complexity of Cancer Cell Signaling Alterations

Because crosstalk allows alteration of one signaling pathway to influence the behavior of otherwise distinct pathways, an alteration originating within a single pathway in a cancer cell can produce consequences that extend into other, seemingly unrelated pathways through crosstalk, contributing to the broader and interconnected pattern of signaling alteration frequently observed across cancer cell signaling as a whole.