Paracrine signaling

Paracrine signaling is local cell-to-cell communication in which secreted molecules act on nearby cells, typically without entering systemic circulation.

Ligand: A molecule that binds specifically to another molecule, often a receptor. Paracrine signals act as ligands when they bind receptors on nearby target cells.
Autocrine signaling: Cell communication in which a secreted signal acts on the same cell that released it. It differs from paracrine signaling because the signal returns to its producing cell.
Morphogen: A signaling molecule that produces different cell fates at different concentrations across a developing tissue. Paracrine morphogens pattern tissues by forming gradients that nearby cells interpret.
Hedgehog signaling pathway: A conserved signaling pathway that regulates embryonic patterning and tissue maintenance. Secreted Hedgehog proteins can act across neighboring cells to specify developmental patterns.
Receptor: A molecule, usually a protein, that detects and binds a specific signal. Target-cell receptors determine which nearby cells respond to a paracrine signal.
Endocrine signaling: Cell communication in which hormones travel through circulation to affect distant target cells. It contrasts with paracrine signaling’s local reach and lack of systemic transport.
Angiogenesis: The formation of new blood vessels from pre-existing vessels. Paracrine factors released by tissues recruit and guide endothelial cells during vessel growth.
Wnt signaling pathway: A family of signal-transduction pathways activated by secreted Wnt proteins. Wnt proteins often convey local developmental and tissue-maintenance cues between nearby cells.
Signal transduction: The conversion of a detected signal into a series of intracellular events and responses. Receptor binding converts an extracellular paracrine cue into changes inside its target cell.
Synaptic transmission: Communication in which a neuron releases neurotransmitter across a specialized synaptic cleft to a target cell. It is a more spatially restricted, specialized form of local chemical communication.

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