Which of the following is NOT a characteristic of paracrine signaling?
Paracrine signaling is short-range communication where secreted proteins travel tens to hundreds of micrometers through extracellular matrix, binding receptors on nearby cells. It involves ligand-receptor interaction, gradient formation, endocytic clearance and threshold-dependent gene activation, exemplified by FGF, Hedgehog, Wnt and TGF-beta families patterning embryonic fields. Communicating with distant organs requires endocrine signaling via bloodstream, such as insulin, estrogen or growth hormone traveling systemically and acting at low concentration. Paracrine cannot act systemically du
Ref: Alberts, Molecular Biology of the Cell, 6th ed., Chapter 15: Paracrine vs Endocrine Signaling.
