Assumed structure of signaling pathways. This figure depicts a signal transduction pathway. The source proteins are cell-surface proteins that transduce the signal to intermediate (cytosolic) proteins. These in turn transduce the signal to the target proteins (TFs), that regulate the transcription of downstream genes. A dotted line between two proteins indicates a PPI.
Supper et al. BMC Systems Biology 2009 3:67 doi:10.1186/1752-0509-3-67